The effects of resistance exercise on lipid peroxidation, bone metabolism, and physical performance in adults aged 60-85...

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The effects of resistance exercise on lipid peroxidation, bone metabolism, and physical performance in adults aged 60-85 years.
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Thesis (Ph.D.)--University of Florida, 1999.
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Includes bibliographical references (leaves 180-192).
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by Kevin Robert Vincent.
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Typescript.
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Vita.

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THE EFFECTS OF RESISTANCE EXERCISE ON LIPID PEROXIDATION, BONE
METABOLISM, AND PHYSICAL PERFORMANCE IN ADULTS AGED 60-85
YEARS.











By

KEVIN ROBERT VINCENT


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE
UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

1999














Copyright 1999

By

Kevin Robert Vincent














This dissertation to dedicated to:

My wife Heather. Her love and support has guided me through this process. For that, I
can never thank her enough.

Michael L. Pollock, Ph.D. I hope that he is as proud of this work as I am of being his
student.

My parents, James and Mary Ellen Vincent. Their love and support has provided me the
foundation for who I have become. I am very proud to be their son.














ACKNOWLEDGMENTS


An endeavor such as this one cannot be accomplished by one person alone.

Throughout my doctoral career at the University of Florida I have been fortunate to meet

and work with many outstanding people. I hope that I have touched their lives as they

have touched mine.

I would like to acknowledge Dr. Michael L. Pollock, my first advisor at the

University of Florida. He was the reason I chose to attend this university. I will always

cherish the opportunity I had to work with and to get to know him. Thank you for

everything "Big Mike"!

I would also like to express my gratitude to Dr. Randy W. Braith. His support,

guidance, and friendship over the past year have been greatly appreciated. Whenever I

had a question or just needed to talk, he was always available. I could not have

accomplished this project without him.

I would like thank my doctoral committee members: Dr. David Lowenthal, Dr. Jeff

Bauer, and Dr. Charles Wood for all of their assistance throughout my doctoral career.

Their advice and friendship helped to guide my studies as well as my life.

The friends that I have made at Florida have made this entire experience

worthwhile. I would like to express my sincerest thanks and appreciation to Shannon

Lennon, Rachel Cutler, Ross Feldman, Pete Magyari, and Chris Hass. You were all there








for me when I needed a shoulder to lean on or some help with data collection. I will

always cherish our friendship.

I would like to thank Michelle Brown for her seemingly endless patience during

this project. She was always there to listen to my frustrations and she allowed me the

time necessary to work on this study. I can never thank her enough for her support.

Finally, I would like to thank my wife, Heather Vincent. I cannot express how

much I appreciate the help and support that she has given me, not only during graduate

school, but with life. I would not be where I am without her.












TABLE OF CONTENTS


ACKNOWLEDGMENTS. .

ABSTRACT .....

CHAPTERS

1 INTRODUCTION ..


Justification for Research .
Purpose and Specific Aims.
Research Hypotheses ..
Significance of Research .


2 REVIEW OF RELATED LITERATURE .. ....
Age-Related Alterations in Muscle Mass, Structure, and Strength
Decreased Muscle Mass .. .....
Motorneuron Decline with Aging ...
Neuromuscular Performance Changes with Aging
Muscle Mass and Strength Increases with Resistance .
Exercise in Older Adults
Postural Control and Aging .. .....
Resistance Exercise and Balance and Physical Function .
Bone Formation and Resorption .. ....
Resistance Exercise and Bone Mineral Density .. ..
Oxidative Stress and Free Radical Production ..
Free Radicals and Aging .. ........
Exercise and Oxidative Stress ...
Exercise Prescription for Older Adults ...

3 METHODS .. .......


Subjects .
Subject Eligibility .
Inclusion Criteria .
Exclusion Criteria .
Study Design .
Experimental Protocol .. ..


. iv


I









Visit 1: Screening/Orientation .
Visit 2: Treadmill Graded Exercise Test .
and Blood Sample Collection
Visit 3: Muscular Strength Assessment .
Visit 4: Muscular Endurance .
Visit 5: Bone Mineral Density .
Visit 6: Balance, Stair Climbing, and Isometric .
Lumbar Extension Strength
Visit 7: Body Composition and Muscular Strength Assessment .
Training Period: Six Months of Dynamic Resistance Exercise
Biochemical Assays .
Markers of Bone Metabolism .... .
Alkaline Phosphatase-B .
Osteocalcin .
Pyridinoline Crosslinks .
Biochemical Indicators of Oxidative Stress .
Lipid Peroxidation Measurements .
Oxidative Challenges in vitro ... .
Xanthine-Xanthine Oxidase System .
(Superoxide Generator)
Hydrogen Peroxide System .
Ferric Chloride System (Hydroxyl Generator) .
Statistical Analyses .

4 RESULTS ........


Subject Characteristics ..
Aerobic Endurance ..
Oxygen Consumption ..
Treadmill Time to Exhaustion.
Time to Ascend One Flight of Stairs .
Changes in Muscular Strength
Chest Press ..
Leg Press .. ...
Leg Curl .
Biceps Curl ..
Seated Row .. ...
Overhead Press ..
Triceps Dip ..
Leg Extension ..
Total Strength .. ..
Muscular Endurance .. ..
Chest Press ..
Leg Press .. ...
Lumbar Extension Strength .


S36
. 37

S 39
S40
S40
S 41

42
44
S 45
S 45
S45
S46
S46
S47
S47
S47
. 48

S 48
S 48
S 48









0 of Lumbar Flexion 59
12 of Lumbar Flexion 59
24 of Lumbar Flexion .. 59
36 of Lumbar Flexion 60
48 of Lumbar Flexion ..... 60
60 of Lumbar Flexion ... 60
72 of Lumbar Flexion .. 60
Total Lumbar Extension Strength. 62
Bone Mineral Density .. 62
Total Body Bone Mineral Density 62
Femoral Neck Bone Mineral Density. 62
Anterior/Posterior Lumbar Spine Bone Mineral Density 62
Lateral Lumbar Spine Bone Mineral Density 63
Ward's Triangle Bone Mineral Density.. .. .. 63
Correlations Between Physiological Performance Variables 63
and Muscular Strength
vo2 ... .. 64
Treadmill Time to Exhaustion. 64
Stair Climbing Time .68
Correlations Between Physiological Performance Variables and 68
Bone Mineral Density
Total Body 68
Femoral Neck. 69
Ward's Triangle....... .69
Anterior/Posterior Lumbar Spine 69
Lateral Lumbar Spine. 70
Biochemical Analyses. 71
TBARS 71
Lipid Hydroperoxides..... 71
Serum Osteocalcin 72
Serum Bone-Specific Alkaline Phosphatase .72
Serum Pyridinoline Crosslinks. 72

5 DISCUSSION 146

Overview and Principal Findings .146
Muscular Strength, Muscular Endurance, and Stair Climbing 147
Muscular Strength. 147
Muscular Endurance 149
Stair Climbing Ability 150
Physiological Significance of Strength Data .. .. 150
Aerobic Endurance 151
VO1 a .. 151
Treadmill Time to Exhaustion. 154
Bone Mineral Density and Bone Metabolism 155









Bone Mineral Density .
Biochemical Markers of Bone Metabolism .
Physiological Significance .
Lipid Peroxidation and Resistance to Oxidative Stress
Physical Challenge in vivo ....
Oxidative Challenge in Vitro ..
Physiological Consequence and Significance .
Major Conclusions .
Physiological Significance ...
Limitations to the Experiment and Future Directions.


APPENDICES


A A-PRIORI SAMPLE SIZE ESTIMATION AND POWER ANALYSIS
B INFORMED CONSENT TO PARTICIPATE IN RESEARCH .
C INSTITUTIONAL REVIEW BOARD APPROVAL FORM TO.
PERFORM RESEARCH

REFERENCES ........

BIOGRAPHICAL SKETCH .......


155
. 157
158
. 159
160
162
. 163
163
164
. 165













Abstract of Dissertation Presented to the Graduate School of the University of Florida in
Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy

THE EFFECTS OF RESISTANCE EXERCISE ON LIPID PEROXIDATION, BONE
METABOLISM, AND PHYSICAL PERFORMANCE IN ADULTS AGED 60-85
YEARS.



By

Kevin Robert Vincent

August 1999


Chairman: Randy W. Braith
Major Department: Exercise and Sport Sciences

The purpose of this investigation was to examine the effects of circuit resistance

exercise training (CWT) at two different intensity levels on physical function, bone

metabolism, and lipid peroxidation in elderly persons. Sixty-two men and women (age

68.16.3 yr.) completed the study. Participants were randomized into three groups: high-

intensity (HEX, 80% of 1RM for 8 repetitions, n=22), low-intensity (LEX, 50% of IRM

for 13 repetitions, n=24) and control (CON, n=16). HEX and LEX groups trained 3x/wk

for 6 months using 11 machines. All groups were tested pre- and post-training for aerobic

capacity (V024,), treadmill time to exhaustion, IRM on the chest press, leg press, leg

curl, leg extension, seated row, overhead press, biceps curl, and triceps dip, chest press

and leg press endurance, time to walk up one flight of stairs, regional bone mineral density

(BMD), serum markers of bone metabolism, and serum lipid peroxidation (LIPOX). Both








training groups significantly increased IRM strength for all 8 exercises (p<0.05). Total

strength increased 17.2 and 17.8% for the LEX and HEX groups, respectively (p<0.05).

VO2.k increased 23.5 and 20.1% for the LEX and HEX groups, respectively (p<0.05).

Treadmill time increased 26.4 (p<0.05) and 23.3% for the LEX and HEX groups,

respectively. Time to ascend one flight of stairs decreased by 7.3 (p<0.05) and 5.79% for

the LEX and HEX groups, respectively. Chest press endurance increased by 75.5 and

68.0%, and leg press endurance increased by 79.2 and 105% for the LEX and HEX

groups, respectively (p<0.05). Femoral neck (BMD) increased significantly for the HEX

group (p<0.05). Osteocalcin increased significantly for the LEX and HEX groups, and

alkaline phosphatase increased for the HEX group (p<0.05). Both the LEX and HEX

groups demonstrated significantly lower levels ofLIPOX immediately after the graded

exercise test when compared to CON (p<0.05). The results of this study indicate that one

set of either low- (50% 1RM) or high- (80% 1RM) intensity resistance exercise is

sufficient to increase strength VO2peak, regional BMD, bone turnover, and decrease

exercise-induced LIPOX in older adults.














CHAPTER 1
INTRODUCTION


Aging is associated with decreases in strength, muscle cross-sectional area, bone

mineral density, and physical function (Fiatarone et al., 1994, and Tseng et al., 1995).

Aging is also associated with an increase in oxidative stress. It has been proposed that

aging is a consequence of the interactions of oxygen free radicals with cell components

throughout life (Ji, 1994). Free radicals have been implicated as contributors to cell

membrane disruption, atherosclerosis, and sarcopenia (Weindruch, 1995).

During the aging process, indices of free radical formation increase (Ji et al.,

1990). This increase results in an increase in antioxidant enzyme levels to act as defense

against oxidative stress (Ji, 1993). An increased rate of free radical generation is a signal

for an increase in antioxidant enzyme activity (Jenkins, 1988). Numerous investigations

have shown that acute and chronic exercise can result in an increase in antioxidant enzyme

activity (Ji, 1993, Ji et al., 1991, and Tullson et al., 1994). Aerobic endurance exercise,

particularly intense endurance exercise, produces free radicals that upregulate antioxidant

enzyme activities (Tullson et al., 1994). It was recently demonstrated that intermittent

sprint cycling performed three times per week for 6 weeks followed by a seventh week

with five sessions increased antioxidant enzyme activity (Hellsten et al., 1996).

Resistance exercise induces a metabolic stress similar to that seen during sprint

exercise. Therefore, resistance exercise may elicit similar increases in antioxidant enzyme








activity observed during sprint exercise. It has also been shown that transient ischemia

followed by reperfusion can also increase antioxidant enzyme activity (Das et al., 1993).

Muscular contractions greater than 40% of the maximal voluntary contraction (MVC), as

seen during resistance exercise, result in transient blood flow occlusion in the exercising

muscle (Donald et al., 1967). Thus, resistance training may subject skeletal muscle to a

form of ischemia/reperfusion that could possibly result in an increase in antioxidant

enzyme activity leading to improved defense against oxidative stress. Since free radical

formation has been implicated as a possible cause for many debilitating conditions

associated with aging, it is important to ascertain which interventions are effective in

decreasing oxidative stress.

Aging has been associated with a decrease in muscle mass and strength (Larsson et

al., 1979). This decrease in strength is linked to decreased mobility, physical function, and

increased risk of falling in older people (Bendall et al., 1989 and Fiatarone et al., 1990).

Resistance exercise has been shown to be effective for increasing muscle mass, strength

and physical function in elderly adults (Fiatarone et al., 1990, Fiatarone et al., 1994, and

Verfaillie et al., 1997). The Surgeon General's Report on Physical Activity and Health

states that developing muscular strength can improve one's ability to perform tasks and

reduce the risk of injury (Surgeon General, 1996). Furthermore, the report states that

"resistance training may contribute to better balance, coordination, and agility that may

help prevent falls in the elderly (Surgeon General, 1996)."

Resistance exercise also improves physical function by decreasing the relative

intensity of tasks performed in daily life. Resistance exercise can decrease the stress








placed on the heart during lifting tasks such as lifting moderate to heavy boxes which has

been implicated as a cause of heart attacks (McCartney et al., 1993).

Osteoporosis is a degenerative disease that is characterized by a decrease in bone

mineral density (BMD). This loss makes the bones more susceptible to fractures.

Research has indicated that bone formation can be stimulated by placing a strain on the

bone such as during resistive exercise (Rubin and Lanyon, 1984). Braith et al. (1996)

examined the effects of 6 months of resistance exercise on BMD following heart transplant

surgery. Typically, BMD decreases during the post-operative period as a consequence of

glucocorticoid therapy. The group that performed strength training was able to return

their lumbar, total body, and femoral neck BMD to near baseline levels while the control

group's BMD remained depressed. Isolated strength training of the lumbar muscles has

also been shown to increase lumbar BMD. Pollock et al. (1992) showed that 6 months of

isolated lumbar training improved lumbar BMD compared to controls in men and women

60 to 79 years of age. Menkes et al. (1993) reported a significant increase in femoral neck

BMD in middle-aged to older men following 16 weeks of strength training. Resistance

exercise can also have a significant effect on biochemical markers of bone metabolism.

For example, Menkes et al. (1993) reported significant increases in osteocalcin and

skeletal alkaline phosphatase isoenzyme (markers of bone formation) and a significant

decrease in tartrate-resistant acid phosphatase (marker of bone resorption) following 16

weeks of training. However, the results of this study were not replicated in another 16

week study by the same group (Ryan et al., 1994). It is possible that the duration of

training was not adequate to elicit a consistent alteration in the levels of these markers.








A factor that makes comparison of many of the investigations mentioned in this

review difficult is that some used high intensity resistance exercise while others used lower

intensity levels. Therefore, comparisons of their results or the ability to make appropriate

recommendations is difficult or impossible. The current intensity recommendation for

adults over 50 years of age corresponds to 14 to 16 (hard) on the Borg RPE scale

(Pollock et al., 1994). The intensity should be perceived as hard by the participant, but

should not be to voluntary failure as is recommended for younger adults (ACSM, 1990).

This recommendation for people over 50 yr. is not based upon scientific evidence and it is

not known if elderly people need to work at the same intensity as younger adults to derive

similar benefits, or if a lower intensity is sufficient. Therefore, the purpose of the proposed

investigation is determine what level of intensity is necessary for improved physical

function, bone metabolism, and defense against oxidative stress.



Justification for Research

Resistance exercise can have a significant impact on bone mineral density, strength,

physical function, and balance. Also, recent studies have demonstrated that elderly

persons can show similar adaptations to resistance exercise when compared to younger

adults. However, what is not known is if there is an intensity threshold for these

adaptations. It is also unknown if the same intensity is necessary to elicit these changes or

if they each respond to a different intensity. Since a large portion of the American

population is growing older, it is important to know what is the threshold intensity that

should be recommended to these people to improve health.








To date, no published investigations have examined if resistance exercise can

improve antioxidant defense systems. It has been shown that endurance exercise can

increase antioxidant enzyme activities (Powers et al., 1994). If resistance exercise can

increase these enzymes it could be recommended as another means of combating oxidative

stress. What is also necessary to determine is if low or high intensity exercise is necessary

to elicit adaptations in the endogenous antioxidant defense system.

It has been shown that resistance exercise can positively impact bone mineral

density, and improve balance and physical function. Although both low and high intensity

resistance exercise can affect all of the previously mentioned parameters, we sought to

determine if a greater impact will be made by high intensity training.



Purpose and Specific Aims

The purposes of this investigation were twofold: (1) To examine the effects of 6

months of dynamic resistance exercise training at two different intensity levels on physical

function, bone metabolism, aerobic endurance, and alterations in lipid peroxidation in

older adults. (2) To determine if the various physiological adaptations to 6 months of

resistance exercise vary between two intensity levels of resistance training. Specifically,

the aims of this study were to examine the consequences of low and high intensity

resistance exercise on:

1. Muscle strength: Measured by 1-repetition maximum (1-RM) for the chest

press, leg press, leg curl, biceps curl, seated row, overhead press, triceps dip, and

leg extension.








2. Muscle endurance: Measured by maximum number of repetitions performed

using 60% of the pre-training 1-RM for chest press and leg press.

3. Physical function: Measured by time to climb one flight of stairs

4. Bone metabolism: Measured by assaying for serum levels of pyridiniline

crosslinks, osteocalcin, and skeletal alkaline phosphatase enzyme.

5. Bone mineral density: Measured by dual-energy photon absorptiometry (DXA)

6. Serum oxidative stress measured by lipid peroxidation.

7. Aerobic endurance measured by a symptom-limited graded exercise test, and

time to exhaustion measured during the graded exercise test.



Research Hypotheses

The purpose of this investigation was to examine how dynamic resistance exercise

training at two different intensity levels affected strength, aerobic endurance, bone

metabolism, and lipid peroxidation older adults. This experiment was designed to test two

hypotheses. The first was that six months of resistance exercise would improve "health-

related" adaptations including bone metabolism, defense against lipid peroxidation, aerobic

endurance, physical function, and strength. The second hypothesis was that high-intensity

resistance exercise would not cause greater improvements in muscle strength and

endurance, aerobic endurance, serum markers of bone turnover, bone mineral density, and

serum lipid peroxidation when compared to low-intensity resistance exercise.








Significance of Research

Aging is associated with decreases in strength, muscle mass, physical function,

balance, and increased oxidative stress. Muscle weakness has been shown to be an

important contributor to risk of falling in older people (Nevitt et al., 1991). It is estimated

that the acute care costs associated with falls is in excess of $10 billion (Tinetti et al.,

1994). It is further estimated that insufficient strength to perform activities of daily living

incurs an additional $7 billion in health care costs (Rowland and Lyons, 1991). Decreased

muscular strength can lead to loss of physical independence, increased risk of injury, and

long term disability or institutionalization. Since the proportion of the population over 60

years of age is increasing, it is important to identify feasible interventions that can maintain

quality of life as people age. Resistance exercise has been shown to be an effective means

of improving strength and physical function in people of all ages. However, it is necessary

to obtain data which indicates what is the appropriate quantity and quality of resistance

exercise necessary to promote improved health and function. It is currently unknown if

there is an intensity threshold for health-related adaptations to resistance exercise for older

adults. The American College of Sports Medicine has recognized that resistance training

is important for quality of life and physical function for older adults (ACSM, 1990, 1998).

However, the recommendations for the quantity or quality of this exercise is not based on

an abundance of scientific evidence, rather it is based on the opinions of experts in the

field. There are data to support the beneficial effects of resistance exercise for this

population, but not what the appropriate intensity level is to attain these benefits. The

current intensity recommendation for adults over 50 years of age corresponds to 14 to 16

(hard) on the Borg RPE scale (Pollock et al., 1994). The intensity should be perceived as







8

hard by the participant, but should not be to voluntary failure as is recommended for

younger adults (ACSM, 1990). However, as stated, this recommendation for people over

50 yr. is not based upon scientific evidence and it is not known if elderly people need to

work at the same intensity as younger adults to derive similar benefits, or if a lower

intensity is sufficient. If a greater impact were to be made by high intensity training then

more definitive recommendations to the public can be made. However, if there is no

difference between groups, then the low intensity exercise would be the best

recommendation because it may be associated with a greater adherence rate as compared

to high intensity.














CHAPTER 2
REVIEW OF RELATED LITERATURE


Age Related Alterations in Muscle Mass. Structure and Strength

Decreased Muscle Mass

Aging is associated with a progressive loss of muscle mass and consequently

strength. This age related decline in muscle mass is termed sarcopenia (Evans, 1995). As

a result of the decrease in muscle mass and strength, older individuals can experience

decreased balance, physical function, bone mineral density, independence, and lowered

metabolic rate which contributes to alterations in body composition (Evans, 1995,

McComas, 1996, and Porter et al., 1995).

Aging is accompanied by a loss in fiber size and number (McComas, 1996). Lexell

et al., (1983) reported that elderly men (70-73yr) had 25% fewer muscle fibers in the

vastus lateralis compared to younger men (19-37 yr.). Lexell et al. (1988) also showed

that men in their 80s have 50% the number of fibers compared to younger individuals. The

results also showed that only 10% of the muscle area was lost by age 50, and that after

that point the loss in mass accelerated.

Numerous investigations have reported that the type II fibers experience the

greatest degree of atrophy ( Grimby et al., 1982, Klitgaard et al., 1990, Lexell et al., 1988,

1991, and Tomlinson et al., 1969). This selective reduction in type I muscle size may be

the result of decreased activity leading to disuse atrophy of the high force motor units.









Lexell et al. (1988) demonstrated that the age related decline in muscle mass is mainly

accounted for by type II fiber atrophy with very little contribution from type I fibers.

However, it has also been shown that although the type II fibers experience more atrophy

(decreased cross-sectional area), the relative proportion of type I to type II fibers remains

largely unchanged with age (Grimby et al., 1982,1984, and Lexell et al., 1988). Lexell et

al. (1988) reported that the proportion of type I fibers was 51% at 20 yr. and 55% at 80

yr. It has also been shown that the "mosaic" muscle pattern that is evident in the muscles

of younger individuals is lost with age (Klitgaard et al., 1990). There is typically an

intermixing of motor units so that similar fiber types are not grouped together in one area.

Data from Klitgaard et al. (1990) indicate that muscle fibers in older adults may

experience histochemical alterations in myosin heavy chain (MHC) expression. They

reported that fibers may contain more that one MHC isoform such that type IIA and IIB

or type I and HA isoforms may be found together. The authors felt that this could be the

result of a dynamic equilibrium between fiber groups resulting from disuse, denervation,

or both.

Other studies have reported further histological alterations in aging muscle

(Tomlinson et al., 1969, McComas, 1996). These alterations include: macrophage

infiltration, hyaline degeneration, disorganized sarcomeres, lipofucshin pigmentation,

decreased mitochondrial size, and increased connective tissue.



Motomeuron Decline with Aging

Aging is accompanied by a decrease in the number ofmotorneurons, particularly

the larger alpha-motorneurons (Ansved and Larsson, 1990, Kawamura et al., 1977, and







11

Tomlinson and Irving, 1977). Once denervated, the muscle quickly atrophies, losing 50%/

of its weight in one month and the rate of decline is more rapid for old animals when

compared to young (Gutmann, 1962, and White and Vaughan, 1991). Ansved et al.

(1991) and Einsiedel and Luff (1992) have shown that older neurons are not able to

demonstrate the same degree of collateral sprouting as compared to younger neurons.

This may be the result of decreased protein synthesis and a decreased rate of axonal

transport that is observed with old age (Ansved et al., 1991). Ansved et al. (1991) also

reported that preferential loss during aging is observed in large, fast-conducting

motorneurons with low oxidative enzyme activity that innervate fast-twitch muscle fibers.

In an examination of the extensor digitorum brevis, Campbell et al. (1973)

reported that prior to the age of 60, the number of functioning motor units shows little

change, but there is a progressive decline in functional motor units beyond that age.

Similar results have also been reported for the biceps, soleus, and the thenar muscles

(McComas, 1996). Campbell et al. (1973) also reported that the mean amplitudes of

motor unit potentials are significantly larger in the elderly when compared to younger

controls. These results indicate that when certain muscle fibers become denervated, other

motorneurons reinnervate the fiber by sending out new axonal branches (McComas,

1996). Studies using electromyography have shown that the number of motor units

decreases while the size of the motor units increases with age (Campbell et al., 1973,

Doherty et al., 1993a, 1993b). Although it has been established that motorneurons

decrease with age, the mechanism for this decline is currently not known. However, there

are several proposed mechanisms for neuronal death with age. These proposed

mechanisms are: ischaemia, accumulation of neurotoxins, free radical damage, and that








neurons may be genetically programmed to die at a certain age (McComas 1996, and

Weindruch, 1995).



Neuromuscular Performance Changes with Aging

The consequence of a decrease in motor units and more homogenous fiber

grouping is a decline in contractile function within the muscle. In an examination of the

triceps surae muscle in elderly subjects, Davies et al. (1986) reported that both the time to

peak tension and the time to relaxation were both significantly increased for evoked

twitches. A similar finding was reported for both the plantar and dorsiflexors

(Vandervoort ad McComas, 1986). The results from Vandervoort and McComas (1986)

also indicated that twitch time increased linearly with age (from 20-100yr.) but that a

significant decrease in muscle strength did not occur until the subjects were in their 60's.

The increase in contraction time is likely the result of a decrease in type II fibers. It is also

interesting to note that in the Vandervoort and McComas (1986) study the gastrocnemius

which contains more fast twitch motor units than the soleus showed a greater age related

decline in contractile function.

Fatigability has also been examined but the results from these investigations has

been equivocal (Davies et al., 1986, Klein et al., 1988, Larsson and Karlsson, 1978,

Lennmarken et al., 1985, and Narici et al., 1991). Narici et al., 1991 reported a decrease in

fatiguability with age while Lennmarken et al.(1985) observed an increase in fatiguability

in a similar study. Klein et al. (1988) reported no differences in fatiguability using the

triceps surae muscle, while Davies et al. (1986) found a decrease in fatiguability using the

same muscle group. These studies may be limited by the fact that although similar muscle









groups were used, the frequency of stimulation for the evoked contractions varied

between investigations. Larsson and Karlsson (1978) had subjects perform a sustained

voluntary contraction, and reported that fatiguability was similar for older and younger

adults. It is interesting to note that although there is an increase in the proportion of type

I fibers with age, fatigability is not altered. This may be the result of decreased physical

activity that is seen with aging.

As a consequence of increased contraction time, the elderly muscle's ability to

generate power is compromised (Bassey et al., 1992), as well as, the ability to generate

force during protective reflexes (Vandervoort and Hayes, 1989). Research has indicated

that the ability to generate force quickly, not the absolute amount of force produced is an

important variable in the prediction of risk of falling (Whipple et al., 1987, Maki and

Mcllroy, 1996).



Muscle Mass and Strength Increases with Resistance Exercise in Older Adults

Numerous recent investigations have demonstrated that resistance exercise is an

effective means for increasing muscle mass and strength (Fiatarone et al., 1990,1994,

Frontera et al., 1988, Klitgaard et al., 1990, Morganti et al., 1995). The purpose of this

section will be to highlight these five studies which represent the findings reported in other

previous, as well as, subsequent investigations.

In a cross-sectional study, Klitgaard et al. (1990) reported that men 68 yr. who

had a history of strength training had similar knee and elbow isometric strengths and

cross-sectional area as compared to 28 yr. endurance trained men. They also reported that

men 68yr. with a history of aerobic exercise or no physical activity had lower knee and









elbow isometric strengths and cross-sectional area as compared to 28 yr. endurance

trained men.

Morganti et al. (1995) resistance trained 20 women (av. age 61yr.) twice per week

for six months. Subjects performed three sets of eight repetitions at 80% of their 1RM for

the double leg press, knee extension, lateral pull-down, trunk extension, and trunk flexion.

Strength was measured for the lat pull-down, leg press, and knee extensions at 6 and 12

months. The results indicated an increase in strength in the training group after 12 months

of 77%, 35%, and 74% for the lat pull-down, leg press, and knee extensions, respectively.

No significant increases in strength were noted at 12 months in the control group.

Fiatarone et al. (1990) resistance trained 10 elderly men and women (mean age

90yr) for 8 weeks. Subjects performed 3 sets of 8 repetitions of knee extensions 3 days

per week. Strength was measured by 1RM and regional body composition was assessed

by computed tomography (CT). The results showed that 1RM knee extension strength

improved by 174%, and that mid-thigh muscle area increased 9%.

Fiatarone et al. (1994) examined the effect of resistance training alone or in

combination with a nutritional supplement in men and women with an average age of 87yr.

Subjects performed 3 sets of 8 repetitions 3 days per week for 10 weeks for the hip and

knee extensors. CT scans of the mid-thigh were obtained to assess changes in muscle

area. The results showed an increase in strength of 113%, but a non-significant increase

of 2.7% in mid-thigh-muscle area. The increase in strength was not related to protein

supplementation.

Frontera et al. (1988) examined the effect of 12 weeks of resistance exercise for

the knee flexors and extensors. They trained 12 men (age range 60-72yr) using 3 sets of 8







15

repetitions performed 3 days per week. At the conclusion of the 12 weeks, knee extension

strength had improved 107% and knee flexor strength had increased 227%. CT scans

revealed an 11% increase total muscle area of the mid-thigh. The authors also reported a

40% increase in urinary 3-methyl-L-histidine which is a marker of protein turnover.

One recent study examined the effects of either high- (80% of IRM for 7

repetitions) or low-intensity (40%/ of IRM for 14 repetitions) on strength, thigh cross-

sectional area, and bone mineral density (Taafe et al., 1996). The subjects were women

aged 65-79 yr. Subjects trained 3 days per week for 52 weeks at one of the two

intensities performing 3 sets of leg press, knee extension, and knee flexion. The authors

reported a mean increase in strength of 59%/ and 41% for the high and low groups,

respectively. Both groups demonstrated a significant and similar increase in type I fiber

area but not type H. Neither group experienced a significant increase in bone mineral

density.

These studies indicate that resistance training is an effective means for improving

strength and muscle mass in older adults. However, the resistance training regimens in

these,as well as, other studies are very similar. Most studies use 3 sets per exercise and

typically 6-15 repetitions, not based on research, but based on either investigator opinion

or studies performed on younger people. It is not known if high volume is necessary to

elicit increases in strength and mass, or if a lower intensity would produce similar results.



Postural Control and Aging

The previously described alterations in muscle mass, strength and motor units that

accompany aging can have deleterious effects on posture and balance. The human body









has been described as a multilink inverted pendulum (Maki et al., 1996). As such, it is

inherently unstable due to the influence of gravity (Maki et al., 1996). Perturbations in

posture or balance are responded to by either controlling the center of mass (COM)

through generating torque at the joints or by altering the base of support (BOS) by

stepping or grasping movements with the limbs (Maki et al., 1996). Perturbations

affecting balance can either be mechanical (i.e. force acting on the body) or informational

(i.e. visual, vestibular, somatosensory) (Maki et al., 1996).

Sensory systems display decreased function with aging. Visual acuity, contrast

sensitivity, depth perception, and dark adaptation are all decreased with aging. Decreased

visual acuity has been implicated as a risk factor for falling because the older person may

not be able to see an obstacle in front of them or see that a curb is ahead while walking on

the street (Alexander, 1996). Other degenerative adaptations such as reduced

proprioception, touch sensitivity, vestibulo-ocular reflex, and the density and sensitivity of

dermal mechanoreceptors are reported with aging (Maki et al., 1996).

As previously mentioned, aging is associated with a decreased skeletal muscle

contraction rate which may impair the ability to rapidly produce force in response to

postural perturbations (McComas, 1996). Available evidence indicates that there is an

association between leg muscle weakness and risk of falling and postural sway (Lord et

al., 1991a, 1991b). Research also indicates that the torque necessary to prevent a fall is

typically within the elderly person's ability. However, what is not, is the ability to

generate the torque quickly (Maki et al., 1996). A common way to measure postural sway

and balance is through measuring changes in center of pressure (COP) during force plate

analysis (Alexander, 1996). Alexander (1996) reported that the maximum peak-to-peak







17

COP excursion or speed of the COP excursion can be used to distinguish between young

and adult postural sway patterns. Maki et al. (1994) reported that the amplitude of

mediolateral COP displacement was found to be the single best predictor of falling risk

compared to other balance measures. The authors indicated that adductor/abductor

strength as well as proprioceptors were most critical to maintaining lateral stability.

Research also indicates that using force plates, and insole pressure sensors provide

a reliable and valid means of assessing balance and postural sway (Alexander, 1996, and

Maki et al., 1996). Other commonly used methods such as questionnaires, one-legged

stance time, and reaching tasks have been shown to measure fear of falling rather than

probability of falling (Alexander, 1996). The use of insole pressure sensors allows for

balance and postural sway during dynamic activities to be measured as well.



Resistance Exercise and Balance and Physical Function

Aging has been associated with a decrease in muscle mass and strength (Larsson et

al., 1979). This decrease in strength is linked to decreased mobility, physical function, and

increased risk of falling in older people (Bendall et al., 1989). Resistance exercise has been

shown to be effective for increasing muscle mass, strength and physical function in elderly

adults (Fiatarone et al., 1990,1994, and Verfaillie et al., 1997). The Surgeon General's

Report on Physical Activity and Health states that developing muscular strength can

improve one's ability to perform tasks and reduce the risk of injury(Surgeon General,

1996). Furthermore, the report states that "resistance training may contribute to better

balance, coordination, and agility that may help prevent falls in the elderly (Surgeon

General, 1996)". Falls have been identified as the most frequent cause of injury related









mortality in the elderly (Fife et al., 1984). Nevitt et al. (1991) conducted a prospective

study to determine the risk factors that lead to injurious falls in the elderly. They reported

that the fallers' ability to protect him- or her-self during the fall affected the risk of injury.

The authors recommended that interventions intended to reduce the risk of falling and

injury should include strength training. Fiatarone et al. (1994) examined the effect of 10

weeks of resistance exercise for the legs only on muscle strength and function in elderly

adults (mean age, 87+ 0.6 yr.). Resistance exercise increased muscle strength, gait

velocity, and stair climbing power. Fiatarone et al. (1990) reported that 8 weeks of

resistance exercise for the leg improved strength and function in nonagenarians (mean age

90+lyr.). Quadriceps strength improved 174% and tandem gait speed increased 48%

following resistance training.



Bone Formation and Resorption

The process of bone remodeling (deposition/resorption) is a continuous and

interdependent process (Marcus, 1991). The two primary cells that are involved in the

process of bone metabolism are the osteoblasts and the osteoclasts. Osteoblasts are

primarily involved in bone formation and come from the differentiation of osteoprogenitor

cells (Mundy, 1993, and Raisz et al., 1993). Osteoclasts are primarily involved with bone

resorption and are formed from tumor cells or leukocytes under the influence of osteoclast

forming cells (Mundy, 1993).

Osteoblasts contain alkaline phosphatase, the protein osteocalcin, and secrete type

I collagen (Calvo et al., 1996). This forms the osteoid which is the site of bone

deposition. Into this collagen matrix Ca" and P04- will be deposited to form







19

hydroxyapatite. As the bone develops it will eventually surround the osteoblast which will

then be incorporated into the bone as the osteocyte. The osteocytes are connected via a

canal system known as the Haversian canals (or canaliculi). These canals allow rapid

communication between the interior and exterior of the bone. The canals allow Ca"and

PO4- to be transmitted from the areas of newly formed interior bone to the outside. This

process is known as osteocytic osteolysis (Marcus, 1991). Osteoblast activity is

stimulated by several factors. Estrogen and testosterone act on response elements

(Estrogen Response Element) within the osteoblast to produce Insulin like Growth Factor

1 (IGF-I) (Martin, 1993). Osteoblasts have membrane receptors for IGF-I and I, and

these receptors can also bind insulin (Martin, 1993). Insulin and the IGFs bind to a

tyrosine kinase receptor that has two sub-units. These sub-units interact with the Insulin

Response Substrate (IRS) to induce glucose uptake and protein transcription. So it can be

seen that insulin helps to promote bone formation. Growth Hormone (GH) also promotes

bone formation and plasma calcium increase because it stimulates the release of IGF-I

from the liver and increases intestinal absorption of Ca" (Arnaud, 1993, and Martin,

1993). IGF-I is an anabolic hormone which stimulates bone growth and formation. The

osteoblast has receptors for IGF and produces it, so the osteoblast can produce a factor

which stimulates osteoblast activity (Raisz et al., 1993). At low levels, Prostaglandin E

helps to promote the formation of osteoblasts and stimulates the production of IGF-I

(Raisz et al., 1993). Other factors which can promote bone formation are gamma

interferon, leukemia inhibitory factor, and retinoic acid. Retinoic acid helps to induce

transforming growth factor beta, and bone morphogenetic protein. Vitamin D3 although

more involved in bone resorption is necessary for bone formation because it increases







20

intestinal absorption of Ca"and P04 ,and increases the number of IGF-I receptors on the

osteoblast membrane (Raisz et al., 1993).

The osteoclast secretes tartrate resistant acid phosphatase which helps to form a

ruffled invagination in the osteoid and facilitate the release of Ca*and P04- (Calvo et al.,

1996). Interestingly, the osteoblast will use this site to deposit new bone. Osteoclast

activity is promoted by several factors. One of the most important is parathyroid hormone

(PTH) which is secreted by the chief cells of the parathyroid gland (Mundy, 1993). PTH

is secreted primarily in response to low serum Ca" levels. Low serum Ca* causes an

increase in cAMP levels in the chief cells which leads to PTH exocytosis (Mundy, 1993).

The release of PTH in response to low Ca" occurs within minutes. PTH release can also

be stimulated by high serum levels of P04- because the P04- can bind to Ca+ so that the

free Ca" levels in serum decrease. PTH stimulates the kidney to increase the reabsorption

of Ca" and increase the excretion ofPO4-. PTH also acts on the osteoblast to cause it to

secrete a factor that stimulates the activity of the osteoclast to increase osteocytic

osteolysis (Mundy, 1993). This will also serve to increase plasma levels of Ca" and PO4-.

PTH cannot stimulate osteoclasts if osteoblasts are not present. This is an example of the

coupling of resorption and formation. Also, PTH inhibits collagen production by the

osteoblast but does promote osteoblast proliferation. PTH also promotes the conversion

of 25-OH-VitD to the active form of 1,25-OH-VitD (VitD3) (Seino et al., 1993). VitD3

formation can be induced by low serum Ca", PO4-, and Vit D3. VitD3 acts in the brush

border of the intestinal villi to increase the number ofCa" transporters enhancing its

absorption (Seino et al., 1993). It also acts to increase the absorption of PO4-. Both PTH

and VitD3 help to increase serum levels of Ca", Vit Da by increasing its intestinal







21

absorption and both by increasing Ca" resorption from bone (Seino et al., 1993). VitD3

acts on cells of the kidney, intestine, liver, and skeletal muscle to produce Calbindin (Seino

et al., 1993). Calbindin acts as a carrier of Ca" effectively decreasing the levels of free

Ca" within cells. Ca" is a very reactive substance and can promote many intracellular

reactions and therefore it is important to keep its free concentration down. VitD3 also

increases Ca" uptake into the sarcoplasmic reticulum in skeletal muscle (Seino et al.,

1993). VitD3 acts on the osteoblast to increase the production ofosteoclast stimulating

factors(Seino et al., 1993). VitD3 is active in bone resorption (stimulates osteoclast

activity), increases serum Ca" (increased intestinal absorption), and bone formation

(increased IGF-I receptors and Ca*/PO4- availability). Once at the site of bone turnover,

several other mechanisms are involved. PTH causes an increase in cAMP within the

osteoblast. This stimulates the production ofPGE2. PGE2 in high levels serves to

increase bone resorption(Raisz et al., 1993). It promotes osteoclast proliferation and

activity. It also helps to initiate the cycle that causes an increase in IGF-I production.

PGE2 increases cAMP levels, which further increases PGE2 levels (autoamplification).

Bone resorption is also stimulated by Interleukin l(IL-1), interleukin-6 (IL-6) and tumor

necrosis factor. IL-6 works by promoting osteoclast congregation.

The final hormone that impacts bone metabolism is calcitonin (Martin, 1993). The

relative effect or importance of calcitonin has not been proved in humans. It responds to

high levels of serum Ca". Its effect is to oppose the actions of PTH and increase Ca"

excretion and possibly promote bone formation.

Estrogen is essential for promoting bone growth (Orimo et al., 1993). Estrogen

increases the osteoblastic production of IGF-I and decreases the production ofIL-1, IL-6,







22

and reduces the sensitivity of the osteoblast to PTH(Hashimoto et al., 1993 and Orimo et

al., 1993). Estrogen also promotes the formation of VitD3. With aging, the production of

estrogen declines (menopause) and the level of PTH in women steadily increases (Orimo

et al., 1993). The age dependent increase in PTH is not seen in men. Also with aging,

glucocorticoid levels increase or are given exogenously. Cortisol decreases the absorption

of Ca" and inhibits bone formation (Raisz et al., 1993). This could also increase the bone

loss in post-menopausal women or in people given glucocorticoids. Another

pathophysiological condition which can cause a large decrease in bone mass is organ

transplantation (Braith et al., 1996). These patients are supplemented with corticosteroids

and cyclosporin which can cause precipitous decreases in bone formation. These patients

are also usually sedentary and the lack of physical activity can decrease bone mass.

Bone formation can be impacted by environmental or pathophysiological factors.

It has been observed that there are seasonal alterations in bone metabolism. During the

winter the elderly or immobile do not go outside. VitD must either be consumed in the

diet or obtained through exposure to sunlight (Seino et al., 1993). If the person is not

exposed to sunlight and this is combined with inadequate VitD intake, then Ca"

absorption and serum levels will be impaired. Under these circumstances, a more

collagenous, soft bone will be deposited due to the lack ofCa" and P04-(Seino et al.,

1993) Winter conditions can also lead to decreased physical activity. Physical activity has

been shown to be a determinant of bone mineral density (BMD). Physical activity such as

strength training and running which cause skeletal loading can increase BMD. The

osteoclasts and lining cells of the bone contain mechanoreceptors. These receptors

respond to increased mechanical or electrical stimulation (Rubin and Lanyon, 1984).









These physical stimuli are translated into biochemical messages. When this occurs an

increase in 2nd messenger activity is observed in the osteoblasts. Within 10 seconds of

mechanical loading, mRNA levels within the osteoclast increase. In the osteoblast, two

second messenger systems are activated. First, adenylate cyclase is activated and cAMP

levels rise. Second, the inositol triphosphate system is activated causing an increase is

inositol diphosphate, protein kinase C, phospholipase A which increase arachidonic acid

entry and formation which leads to the production ofPGE2. PGE2 also increases cAMP

(Raisz et al., 1993). The increase in cAMP and PGE2 causes an increase in IGF-I

production and therefore increased bone formation.


Resistance Exercise and Bone Mineral Density

Osteoporosis is a degenerative disease that is characterized by a decrease in bone

mineral density (BMD). This loss makes the bones more susceptible to fractures.

Research has indicated that bone formation can be stimulated by placing a strain on the

bone as is found during resistive exercise (Rubin and Lanyon, 1984). Hamdy et al.(1994)

reported higher BMD in the upper arm in people that weight trained when compared to

runners, but that there was no difference for lower body BMD between the two groups.

Karlsson et al.(1993) reported that active and retired weightlifters had higher BMD for

the spine, hip, tibia, and forearm when compared to controls.

Kohrt et al. (1997) examined the effect of either exercise involving ground reaction

forces (GRF) or joint reaction forces (JRF) on bone mineral density in women aged 60-74

years. Both groups trained for 11 months with the GRF group performing walking,

jogging, and stair climbing while the JRF group performed resistance training and rowing.







24

The resistance training regimen consisted of 8 exercises performed for 2-3 sets, for 8-12

repetitions two times per week. The results indicated significant and similar increases in

BMD for the whole body, lumbar spine, and Ward's triangle region of the proximal femur

for both groups. Only the GRF group exhibited a significant increase in femoral neck

BMD.

Braith et al. (1996) examined the effects of 6 months of resistance exercise on

BMD following heart transplant surgery. Typically, BMD decreases during the post-

operative period as a consequence of glucocorticoid therapy. The group that performed

strength training was able to return their lumbar, total body, and femoral neck BMD to

near baseline levels while the control group's BMD remained depressed. Isolated

strength training of the lumbar muscles has also been shown to increase lumbar BMD.

Pollock et al. (1992) showed that 6 months of isolated lumbar training improved lumbar

BMD compared to controls in men and women 60 to 79 years of age.

Menkes et al. (1993) reported a significant increase in femoral neck BMD in

middle-aged to older men following 16 weeks of strength training. The mechanism for

how resistance exercise effects BMD has yet to be determined. It is thought that the strain

placed on bone by loading results in a piezoelectric current which causes an increase in

bone formation. Resistance exercise can also have a significant effect on biochemical

markers of bone metabolism. Menkes et al (1993) reported significant increases in

osteocalcin and skeletal alkaline phosphatase isoenzyme (markers of bone formation) and

a significant decrease in tartrate-resistant acid phosphatase following 16 weeks of training.

However, the results of this study were not replicated in another 16 week study by the








same group (Ryan et al., 1994). It is possible that the duration of training was not

adequate to elicit a consistent alteration in the levels of these markers.



Oxidative Stress and Free Radical Production

Free Radicals and Aging

It has been proposed that aging is a consequence of macromolecular disturbances

mediated by oxidative stress (free radical generation)(Harman, 1956, Ji, 1993,and Nohl,

1993, ). Free radicals can be produced in the mitochondria, or in any system that utilizes

oxygen(Yu, 1994). Sites of radical generation are the electron transport chain

(Ubiquinone, Coenzyme Q) and cytochrome P450 in the nucleus as well as other

locations. It has been shown that the mitochondria are prime sites of free radical

production and that damage to DNA is 16 times higher in the mitochondria than in the

nucleus (Yu, 1994). It has also been shown that the mitochondria of aged animals shows

more superoxide (0-) leakage than that of younger animals(Nohl, 1993). Also, free

radicals are produced by xanthine oxidase (XO). During exercise, ATP is converted to

adenosine. At the same time, Xanthine dehydrogenase is converted to XO by the increase

in intracellular calcium seen during exercise. XO acts on the adenosine byproducts to form

uric acid (a free radical) (Yu, 1994).

Oxidative stress is defined as an imbalance between free radical production and the

forces that oppose their production (Jenkins, 1988). Free radicals are also called reactive

oxygen species (ROS). The various forms of free radicals produced are superoxide (02-),

hydroxide (OH), and hydrogen peroxide (H202). These radicals can then take electrons

from other substances and form other radicals and cause damage to biological systems.








Common sites for damage are molecules containing sulfhydryl groups (proteins, gates,

DNA), double bonds (Polyunsaturated Fatty Acids, PUFA in membranes), and

carbohydrates (Reid, 1996, and Yu, 1994). The primary defense against this type of

damage includes the enzymes superoxide dismutase (SOD), glutathione peroxidase (GPX)

and catalase (CAT). SOD is an enzyme located in the mitochondrial membrane, cytosol,

and plasma (Jenkins, 1988). It scavenges superoxide radicals and converts them to H202.

Although this is still a ROS, it is less reactive than superoxide. H202 can be rendered

harmless by two other enzymes. The first is GPX which uses glutathione to accept the

extra electron and converts the H202 to H20. The glutathione is then regenerated by

glutathione reductase with the help ofNADPH from the pentose phosphate pathway.

H202 can also react with CAT. CAT also converts H202 to H20. One postulated reason

for having the two enzymes is that GPX is active at lower levels of H202 and CAT

becomes active with higher levels.

Superoxide can also be scavenged by dietary antioxidants such as vitamin E, beta

carotene, and vitamin C. Typically, vitamin E is used to squelch superoxide or to insert

itself into the membrane to inhibit the propagation of membrane disruption. Free radicals

will use the double bond site of PUFAs in the cell membrane as a place to steal an

electron. This can cause disruption in the membrane because that fatty acid tries to steal

an electron from a neighboring fatty acid. Propagation can result in holes in the cell

membrane. These holes can disrupt the ionic balance of the cell, as well as, allow the

entry of calcium which can activate proteases and cause cellular damage. Vitamin E and

beta carotene are lipid soluble and have long hydrophobic tails. The head of the vitamin E

can accept the free radical and prevent the free radicals from continuing to disrupt the cell







27

membrane. Vitamin E is then recycled through the action of vitamin C and lipoic acid or

through GPX. Although vitamin C is a good antioxidant, it does have a limitation in that

at high levels it can act as a pro-oxidant and promote free radical damage. Lipoic acid

does not scavenge radicals by itself, but rather it serves a supportive function by aiding in

the recycling of vitamin E. Glutathione is the primary thiol scavenger in the antioxidant

defense system. Other minor antioxidants are bilirubin and carbohydrates.

Free radicals and ROS have been implicated as major contributors to the aging

process (Harman, 1956). Aging has been defined as a decreased ability for the cells to

proliferate. This decreased proliferation may be the result of an internal timer within the

cell that when expired, will not allow the cell to survive. It may also be due to impaired

codon transcription (Nohl, 1993, and Yu, 1994), as ROS cross-links proteins. If this

occurred in DNA, then the strand would not be readable. Cross-linking mRNA results in

failure of transcription of the genetic message. Therefore, ROS may be responsible for the

inability to correctly translate the messages found in DNA (Jenkins, 1988, Nohl, 1993, and

Yu, 1994). Ultimately, this could inhibit the cell from proliferating or from correctly

functioning.

Aging is associated with a decrease in muscle mass and strength (sarcopenia). One

cause of a decrease in mass is a loss in muscle fiber number, likely due to a loss of motor

neuron innervation. It has been shown that ROS can negatively impact nerves and either

cause their inactivation or their degeneration (Lou Gehrig's Disease, Parkinson's

disease)(Sohal and Orr, 1992). Therefore, ROS are a potential source ofdenervation and

sarcopenia with aging. ROS can damage the SR and inhibit the release and uptake of

Ca", leading to decreased contractile force. It has been shown in skinned fiber







28
preparations that the integrity of the contractile element in the muscle fiber remains intact

with aging and does not decrease in force capability (Powers et al., 1994). What does

show impairment is the excitation-contraction coupling (Reid, 1996). ROS have also been

implicated in type I and II diabetes (Yu, 1994). It has been shown that ROS can attack

and deactivate the beta cells in the pancreas which stimulate the release of insulin. It has

also been shown that SOD activity is lower in persons with diabetes. Diabetes is a risk

factor for cardiovascular disease (Yu, 1994).

According to Evans (1995), elderly people experience exacerbated muscle damage

compared to young people as a consequence of exercise. This may be due to several

factors. First, when damage occurs (typically from eccentric contractions) in young,

healthy muscle, neutrophils and lysozymes infiltrate the area and release free radicals as a

means of breaking down damaged tissue. Satellite cells which decrease with age are non

differentiated cells that are next to muscle fibers (Carlson, 1995). They help to repair the

fiber, or can even form new ones. In younger mammals, damaged fibers are replaced with

contractile elements, where in older mammals, contractile elements are replaced with non-

contractile elements like collagen. This would decrease the muscles integrity leaving it

more susceptible to damage.

It has also been shown that tissue levels of vitamin E decrease with age (Yu,

1994). This could be from decreased intake or increased utilization. As mentioned

earlier, aging is associated with increased free radical production. It may also be

associated with or the result of an accumulation of damage incurred by ROS over time. Ji

(1993) showed that with aging, skeletal muscle antioxidant enzyme (AOE) activity

increases. Since AOE activities increase as a result of ROS production the increase in








AOE must result from accumulated oxidative stress. This stress may accumulate with

time and cause damage that is outwardly seen as the aging process. Several investigators

have shown that increased metabolic activity has been associated with a shorter life span.

The results have been most clearly demonstrated in fruit flies. When allowed to fly and

mate, their life span decreases compared to those that were kept from flying or

sequestered from the opposite sex.



Exercise and Oxidative Stress

During the aging process, the rate of free radical formation increases (Ji et al.,

1990). This stimulus increases antioxidant enzyme levels that act as defense against this

oxidative stress (Ji, 1993). Increased free radical generation is a signal for an increase in

antioxidant enzyme activity (Jenkins, 1988). Numerous investigations have shown that

acute and chronic exercise can result in an increase in antioxidant enzyme activity

(Hammeren et al., 1992, Ji, 1993, Ji et al., 1991, and Tullson et al., 1994). Aerobic

endurance exercise, particularly intense endurance exercise results in an increase in free

radical generation which also results in increased antioxidant enzyme activities (Tullson et

al., 1994). It has been shown that increasing the metabolic rate or flux of oxygen through

the electron transport system (ETS) promotes ROS generation (Ji, 1993, Powers et al.,

1994, and Reid et al., 1993). As oxygen consumption increases, the possibility of ROS

generation increases. Reid et al. (1993) demonstrated that excessive ROS generation was

related to decreased force production. It has also been shown that ROS can interact with

the sulfhydryl groups on the gates on the sarcoplasmic reticulum and either inhibit the

release or the uptake of Ca" (Reid, 1996). This results in disruption of the force









producing capabilities of the muscle and interferes with excitation-contraction coupling

(Reid, 1996). As mentioned earlier, ROS can also cause membrane disruption in the

cellular membrane which would also cause a breakdown in the ionic gradient necessary for

contractions.

Numerous investigators have shown that SOD and GPX levels increase in

response to exercise training (Ji, 1993, Leeuwenburgh et al., 1994, and Powers et al.,

1994). The effects of exercise on CAT activity is not as clear. Therefore, it seems that

ROS generation causes some adaptation which increases antioxidant enzyme (AOE)

activity. This can occur either through promoting the transcription of more enzymes or

through the allosteric modification of existing enzymes allowing them to be more active.

Free radical production can also result from ischemia followed by reperfusion (Das

et al., 1993). During systole, blood flow to the ventricles is momentarily occluded

(ischemia). During diastole, blood flow is restored (reperfusion). During exercise, the

period of diastole and therefore reperfusion is decreased. This type of cycle has been

shown to increase ROS generation and can cause damage to the myocardium or to the

vasculature (Yu, 1994). A similar ischemia/ reperfusion cycle may be present in skeletal

muscle during resistance exercise. Muscular contractions greater than 40% of the maximal

voluntary contraction (MVC) as performed during resistance exercise result in transient

blood flow occlusion in the exercising muscle (Donald et al., 1967). This form of

ischemia/reperfusion could possibly increase antioxidant enzyme activities that leading to

improved defense against oxidative stress. Recently, McBride et al. (1998) demonstrated

that intense resistance exercise causes an increase in free radical production. Subjects

performed 10 repetitions for 3 sets with 1 minute rest periods between sets for 8 exercises.








The results showed an increase in malondialdehyde (MDA) levels which indicates an

increase in free radical production. A recent investigation has also demonstrated that

intermittent sprint cycling performed three times per week for 6 weeks followed by a

seventh week with five sessions resulted in an increase in antioxidant enzyme activity

(Hellsten et al., 1996). The subjects performed fifteen 10 second maximal sprints with a

50 second rest period between each sprint during each training session(Hellsten et al.,

1996). Resistance exercise induces a metabolic stress similar to that seen during sprint

exercise. Therefore, resistance exercise may elicit similar increases in antioxidant enzyme

activity observed during sprint exercise.

The same exercise-induced increases in free radical production and elevations in

antioxidant enzyme activities have been shown in senescent animals (Ji, 1993,

Leeuwenburgh et al., 1994, and Powers et al., 1994). As a consequence of endurance

exercise, AOE activities were upregulated to the same extent as in younger animals.



Exercise Prescription for Older Adults

The American College of Sports Medicine (ACSM) currently recommends that

resistance exercise be incorporated as a component of a well-rounded exercise program

for all healthy adults (ACSM,1990). The ACSM recommends 1 set of 8-12 repetitions for

younger adults and 10-15 repetitions for adults over 50-60yr., using 8-10 exercises,

performed 2-3days per week (ACSM, 1990, 1998). The greater repetitions for older

adults is used to decrease the risk of orthopedic injuries which may result from lifting

increased loads associated with low volume higher intensity efforts, while the range in age

reflects individual differences towards weakness or frailty. When initiating an exercise






32

regimen for older adults, it is recommended that the initial resistance used should be 30-

40% of their one repetition maximum (1-RM) for that exercise(Pollock et al., 1994). If a

I-RM is not available, start with a low resistance and progress slowly allowing time for

muscle and soft tissue adaptation. The current intensity recommendation for older adults

corresponds to an RPE of 12-13 (somewhat hard) initially (first 4-6 wk) and then progress

to 14 to 16 (hard) on the RPE scale (Pollock et al., 1994). The intensity should be

perceived as hard by the participant, but should not be to voluntary failure as is

recommended for younger adults until approximately 12 weeks (ACSM, 1990). This time

period should be taken as an estimate, the 12 weeks could be lengthened or shortened

depending on the health status or level of fitness of the individual. Once older adults adapt

to their resistance training regimen, most will be capable of progressing to 10-15RM.














CHAPTER 3
METHODS


Subjects

The participants for this study were apparently healthy adults between the ages of

60 and 85 years. Eighty-six participants were entered into the study and sixty-two

completed the protocol. Participants were recruited from the Gainesville, Florida and the

surrounding areas. All participants had not participated in in regular resistance training for

at least one year, but may have been engaged in low-intensity aerobic training equal to or

less than 3 times per week.



Subject Eliaibility

Inclusion Criteria

Subjects were considered eligible for participation if they were:

* aged 60 85 years

* not participating in regular resistance exercise for at least one year

* free from any orthopedic or cardiovascular problems that would limit exercise








Exclusion Criteria

Subjects were excluded from study participation if they:

* Participated in regular resistance exercise during the last year or regular moderate

to high intensity aerobic training.

* had known orthopedic, cardiovascular or non-cardiovascular abnormalities that

would preclude participation in exercise.

* Had any abnormalities identified by the American College of Sports Medicine

(ACSM) as absolute or relative criteria for discontinuing exercise as revealed during a

symptom limited graded exercise test (SL-GXT) (3)



Study Design

This investigation was conducted at the Center for Exercise Science located in the

Florida Gym at the University of Florida. Participants were matched and randomly

assigned to 1 of the following three groups:

low-intensity resistance exercise (LEX)

high-intensity resistance exercise (HEX)

wait list control (CON)

Subjects were matched using a composite strength score calculated by adding the chest

press and leg press one-repetition maximum (1RM) values. Three subjects were matched

using the composite strength score when their pre-testing visits were completed and were

then randomly assigned to one of the three groups. Randomization was performed using a

random numbers table. Muscle strength and endurance, bone metabolism, serum lipid







35

peroxidation, and physical function were measured before and after the 6 month training

period.

Participants were scheduled for seven visits prior to the start of the training period.

Visit 1: Participants read and signed an informed consent, and were given an explanation

of the study. They also received an orientation to the resistance exercise machines and the

treadmill protocol that was used during the graded exercise test. Visit 2: Participants

were given an SL-GXT (Naughton protocol) whereby blood pressure, heart rate, ECG,

and symptoms were monitored by a physician. The GXT was terminated upon volitional

fatigue of the subject and/or according to the guidelines established by the American

College of Sports Medicine (3). A blood sample was also collected before and after the

GXT to measure biochemical markers of bone turnover and antioxidant enzyme capacity.

Visit 3: Participants had their maximum strength measured by determining the maximum

load that they could lift for 1 repetition (1-RM) on the leg press, chest press, leg curl, and

biceps curl. Visit 4: Participants had their muscular endurance measured on the leg press

and chest press. They were asked to perform as many repetitions as possible without

assistance while maintaining proper form using 60% of their previously determined 1-RM.

Visit 5: Each subject had their total body and regional bone mineral density measured

using dual-energy X-ray absorptiometry (DXA). Visit 6: Participants were asked to

ascend one flight of stairs as quickly as possible. Two trials were performed. Maximal

isometric strength for the lumbar extensor muscles was measured using a seven angle

lumbar extension test. Visit 7: Body composition was determined using a seven site

skinfold technique. Participants had their maximum strength measured by determining the








maximum load that they could lift for 1 repetition (1-RM) on the seated row, overhead

press, triceps dip, and knee extension.



Experimental Protocol

Visit 1. Screening / Orientation

All potential participants were recruited from Gainesville and the surrounding area.

Those volunteers who had no contraindications (see exclusion criteria) were asked to

participate in the study. All participants received a comprehensive explanation of the

proposed study, its benefits, inherent risks, and expected commitments with regard to

time. Following the explanation of the proposed study, all participants were allowed a

period of questioning. Those participants who were willing to participate were required to

read and sign an informed consent document, complete a self-reported activity, medical

history, and dietary questionnaires. Participants were then given an orientation to the

resistance exercise machines and equipment used during the GXT by trained personnel.

The resistance exercise equipment for this investigation was MedX resistance machines

(MedX Corp., Ocala, FL). These machines were selected because their design allows for

proper positioning and weight increases for frail or diseased populations. The smallest

increment of load increase is 2 ft-pounds as opposed to 5 or 10 pounds found with other

such exercise equipment. Participants were instructed as to the proper positioning and

exercise form for each machine. Participants performed 10-15 repetitions on each

machine using a light load (20 ft-lb). The machines used for this study were abdominal

crunch, leg press, leg extension, leg curl, calf press, seated row, chest press, overhead

press, biceps curl, seated dip, leg abduction, leg adduction, and lumbar extensions. The







37

participants were then allowed to walk on the treadmill and practice breathing through the

headgear which was used to collect expired air used for the determination of VO2,pi

during the GXT. The subjects walked on the treadmill at 2.0 m.p.h. at a 0% grade for 3

minutes followed by 2 minutes at 2.0 m.p.h. at a 3% grade.



Visit 2. Treadmill Graded Exercise Test and Blood Sample Collection

On visit 2, participants reported to the Center for Exercise after a three hour fast.

Upon arrival participants were seated in a quiet room for 15 minutes where after resting

heart rate (HR), and blood pressure (BP) were obtained using standard auscultation

procedures and a Trimline mercury sphygmomanometer (Pymah Co., Somerville, N.J.). A

medical examination was performed by a physician specializing in geriatric medicine. A 30

ml blood sample was collected via venipuncture of an antecubital vein and used for

measuring bone metabolism and lipid peroxidation. The sample was allowed to clot at

room temperature for 10-20 minutes and then centrifuged for 15 minutes at 0C. The

serum was then pipetted into polystyrene tubes and stored at minus 800C for later analysis.

Samples were analyzed for osteocalcin, skeletal alkaline phosphate isoenzyme, and

pyridinoline crosslinks. Osteocalcin and skeletal alkaline phosphate are markers of bone

formation while pyridiniline crosslinks is a marker of bone resorption. All three

biochemical markers have been shown to be valid indicators of bone turnover and sensitive

to changes with exercise (Menkes et al., 1993, Thorsen et al., 1996). The samples were

collected before the test and repeated within 10 minutes following the conclusion of the

GXT.







38

The subject performed a walking SL-GXT using an incremental treadmill exercise

protocol (Naughton) to determine peak oxygen consumption (VOZp,). The initial

workload was 2.0 m.p.h. at 0% grade and was progressed every two minutes by

increasing the grade 3.5%. Once the test time reached 12 minutes, the treadmill speed

increased to 3.0 m.p.h. and the incline decreased to a 12% grade. From this point, the

grade again increased 3.5% every 2 minutes until the subject reached voluntary maximal

exertion or became symptomatic with positive hemodynamic or medical indices (3). The

following criteria recommended by the ACSM were used for termination of the SL-GXT

(3).

Fatigue

Failure of monitoring equipment

Light-headedness, confusion, ataxia, cyanosis, dyspnea, nausea or any peripheral

circulatory insufficiency

Onset of grade II/III angina pectoris (moderate to severe) with exercise

Mild angina pectoris with 2 mm of ST segment depression

Symptomatic supraventricular tachycardia

ST displacement 4 mm or greater in the absence of angina pectoris

Ventricular tachycardia (3 or more consecutive PVC's)

Exercise induced left bundle branch block

Onset of second and/or third degree A-V block

R on T PVC's (one)

Frequent multifocal PVC's (30% of the complexes)








Excessive hypotension (greater than 20mmhg drop in systolic BP during

exercise)

Excessive BP rise: systolic BP greater or equal to 240 or diastolic BP greater

or equal to 110 mm Hg)

Inappropriate bradycardia (drop in HR greater than 10 beats/min) with an

increase or no change in workload.

During the test, expired gases were collected through a low-resistance one-way

valve (Hans Rudolph). Breath by breath analysis of expired gases was performed

continuously throughout the test using a Medical Graphics Corporation Metabolic Cart

(CPS/Max Medical Graphics TM, St. Paul, MN). The oxygen and carbon dioxide

analyzers were calibrated daily and immediately before and after each test using a known

gas mixture of 12.0% 02 and 5% C02. Ventilatory responses (tidal volume and

frequency of breathing) were measured with a pneumotachograph. Volume calibration was

performed with a 3-liter calibration syringe. Twelve lead electrocardiograms (ECG) were

recorded throughout the test using standard lead placement with a Quinton Q 2000 system

(Quinton Instruments, Seattle, WA). Blood pressure measurements were taken every

other minute using a standard sphygmomanometer and RPE was obtained at the end of

each minute throughout the test using Borg's RPE 6-20 point scale.



Visit 3. Muscular Strength Assessment

During visit 3, dynamic muscular strength was measured using four resistance

exercises which included: chest press, leg press, leg curl, and biceps curl. For each

dynamic exercise, a one repetition maximum (1-RM) was determined. Participants were








properly positioned in the machine and performed a dynamic warm-up using a light

weight. The participant began the test by lifting a light weight and then incremental

increases of 5-10 pounds were made according to the difficulty with which the participant

executed the previous lift. Difficulty was measured by having the participant rate his/her

exertion level using the RPE scale. Two to three minutes rest were given between trials to

prevent premature fatigue. The investigator continued to increase the weight lifted until

reaching the maximum weight that could be lifted in one repetition. This was usually

determined in 5 to 6 trials. Maximal strength was defined as the maximum weight that

could be lifted through a full range of motion with proper form.



Visit 4. Muscular Endurance

During visit 4, assessment of muscular endurance was performed on the chest

press and leg press resistance machines. The participants were properly positioned in the

appropriate machine and allowed a dynamic warm-up with a light weight. The subject

then performed as many repetitions as possible with proper form using 60% of their

previously determined 1-RM. The endurance test for the leg press was always performed

first.



Visit 5: Bone Mineral Density

Bone mineral density (BMD) was assessed using dual energy x-ray absorptiometry

(DXA) (DXA model DPX-L, Lunar Radiation Corp., Madison, WI). DXA is a non-

invasive radiologic projection technique which uses both low and higher energy x-ray

tubes as an energy source. However, radiation exposure is minimal (approximately 1/60







41
of the dose of a chest x-ray). DXA also provides body composition information. During

a DXA scan, the subject was positioned either in a supine or lateral position while the x-

ray scanner performed a series of transverse scans, measured at 1-cm intervals from the

top to the bottom of the region. Four separate skeletal regions were scanned: 1)

anterior/posterior (AP) view of the total body; 2) AP view of the lumbar spine; 3) AP

view of the hips; and 4) lateral view of the lumbar spine.



Visit 6. Balance. Stair Climbing, and Isometric Lumbar Extension Strength

On visit 6, participants were assessed for time to walk up one flight of stairs, and

isolated lumbar extension strength. The participants were asked to walk up a flight of

stairs consisting of 23 steps as quickly as possible. The stairs were 6.5 in. high and 11.5

in. wide. After 14 steps the participants made a left-hand wrap-around turn and then

completed the remaining 9 steps. The participants were not allowed to use the handrails.

The time to complete this task was recorded to the nearest hundredth of a second using a

hand held stopwatch. Participants were required step on all of the steps, taking 2 steps at

a time was not allowed. This test was repeated following a 2-3 minute rest period and the

fastest of the two trials was used for data analysis.

Isometric lumbar extension strength was also tested. Prior to the test, participants

performed a series of stretching exercises and a dynamic variable resistance exercise

session designed to stretch and warm-up the low back, hamstrings, and abdominal areas.

For the dynamic exercise, participants were seated in the MedX isolated lumbar extension

machine (MedX, Ocala, FL) and secured in place by restraints positioned under the feet,

anterior thigh, and posterior pelvis. These restraints restrict movement of the pelvis,








which facilitates isolation of the lumbar extensor muscles. The participants then moved

from flexion to extension through a full range ROM. Men warmed-up with 40 pounds and

women with 20 pounds for 10 repetitions. This series of stretching and dynamic exercises

lasted approximately 10 minutes. Following the dynamic exercise session participants

completed an isometric test of lumbar extensor muscle strength. Seven testing points (0,

12, 24, 36, 48, 60, and 72 degrees of lumbar flexion) were measured for participants who

had a full range of lumbar motion. The specific angles were modified for those

participants with limited ROM. A maximum isometric contraction was generated at each

of these angles beginning with 72 of flexion. Participants were instructed to extend back

slowly building up tension over a 2 to 3 second period. Once maximal tension had been

developed, participants were encouraged to maintain maximal force for an additional 1 to

2 seconds, then slowly relax. Following each isometric contraction was a 10 second rest

period while the next position was set. In this manner a force curve was generated

throughout the ROM for each subject. Participants were given verbal encouragement

during the lifts to ensure a maximal effort.



Visit 7. Body Composition and Muscular Strenath Assessment

On visit 7, the participant had their body composition assessed using skinfolds and

1RM muscular strength was determined for the seated row, overhead press, triceps dip,

and knee extension. The procedure for 1RM determination was the same as for visit 3.

Skinfold measurements were taken to the nearest 0.5 mm on the right side of the body

using a Lange caliper (Cambridge Scientific Industries, Cambridge, MD). Seven sites were

measured: chest, axilla, triceps, subscapular, abdomen, suprailiac, and anterior thigh. The








landmarks and techniques of Pollock and Wilmore (35) were used for the skinfold

measurements:

Chest fold: The skinfold thickness of the chest was measured as an oblique fold one half

the distance between the anterior axillary line and the nipple for men and one third of the

distance from the anterior axillary line and the equivalent position for women.

Axilla fold: The axilla skinfold was measured as a vertical fold on the midaxillary line at

the level of the xiphoid process of the sternum.

Triceps fold: The triceps fold was measured as a vertical fold midway between the

olecranon and acromium process on the posterior of the brachium with the elbow relaxed

and extended.

Subscapular fold: The subscapular fold was taken on a diagonal line coming from the

vertebral border to 1-2 cm from the inferior angle of the scapula.

Abdominal fold: The subject stood erect with body weight evenly distributed on both feet.

The abdominal skinfold was measured as a vertical fold taken 2 cm lateral to and at the

level of the umbilicus.

Suprailiac fold: The suprailiac skinfold was measured from a diagonal fold at the anterior

axillary line immediately above the crest of the ilium.

Anterior thigh fold: A thigh skinfold was be taken with the subject standing with his/her

weight on the left foot, with a relaxed and slightly flexed right leg. The measurement was

made as a vertical fold located on the midline of the anterior aspect of the thigh midway

between the inguinal crease and the proximal border of the patella.








Training Period: Six Months of Dynamic Resistance Exercise

Participants in both the high- and low-intensity training groups were asked to

report to the CES three times per week for 6 months to perform dynamic variable

resistance exercise under the supervision of trained personnel for all machines except the

isolated lumbar extension exercise. Isolated lumbar extensions were performed once per

week under the supervision of personnel certified for the use ofMedX rehabilitation

equipment. Each subject received appropriate instruction concerning warm-up and cool-

down techniques, as well as how to monitor the intensity of the exercise using the RPE

scale. Each subject performed one set on each of the following resistance exercise

machines: abdominal crunch, leg press, leg extension, leg curl, calf press, seated row,

chest press, overhead press, biceps curl, seated dip, and lumbar extensions. There was a 2

minute rest period allowed between each machine. Each set consisted of 8 repetitions for

the HEX group and 13 repetitions for the LEX group at the appropriate resistance load.

To examine the effects of training intensity on the outcome variables and criterion

measures, the LEX group trained at an intensity equivalent to 50% of their IRM, while

the HEX group used loads corresponding 80% of their IRM. For the LEX and HEX

groups, the load was increased by 5% when their RPE rating dropped below 18. The

rationale for training the lumbar extensor muscles only one day per week is derived from

previous research in this lab showing that 1 set of this exercise once per week is adequate

for improvements in lumbar strength and that training more often does not provide

superior results. Prior to the dynamic exercise, participants performed the series of

stretches. Participants were then secured in the lumbar extension machine. Once secure

the subject was instructed to complete a warm-up set of dynamic variable resistance








lumbar extension exercise using 50 percent of their current training weight. Participants

began the dynamic exercise in the fully flexed position (72), extending their trunk back

against the back pad lifting the weightload over a 2-3 second count. After pausing briefly

in the fully extended position (0), the subject was instructed to slowly flex their trunk

forward to the starting position over a 4 second count. The combined movement of

extension, brief pause, and flexion constitutes one repetition. The HEX group performed

10 repetitions, while the LEX group performed 15 repetitions.



Biochemical Assays

Markers of Bone Metabolism

Alkaline Phosphatase-B

The bone-specific alkaline phosphatase isoform (BAP) was measured in serum

using an Alkphase-B(r) enzymatic immunoassay kit (EIA) (Metra Biosystems, Mountain

View, CA, USA). The assay is highly specific for BAP, cross-reacting <=8% with liver

AP and not significantly with other AP isoenzymes. The Alkphase-B kit or EIA used

microtiter stripwell format utilizing a monoclonal anti-BAP antibody and the catalytic

activity of the captured enzyme itself to measure BAP activity in serum. BAP in the

sample binds to antibody coated on the stripwell and the reaction is detected with the

substrate, p-nitrophenyl phosphate (pNPP). Color developed during the incubation of

captured BAP and substrate is measured at 405 nm in a microtiter plate reader. BAP

values of unknown specimens are calculated from a calibration curve fit with a quadratic

equation. Values are expressed in U/L; each unit represents one mole of pNPP








hydrolyzed per minute at 250C in 2-amino-2-methyl-l-propanol buffer. 20 pL of serum

per well (assayed in duplicate) was required for determination of BAP.



Osteocalcin

Osteocalcin (OC) also known as bone gla protein was measured with a

NovoCalcin(r) EIA kit (Metra Biosystems, Mountain View, CA, USA), a microtiter

stripwell format utilizing a murine monoclonal anti-OC antibody.[4] OC in the sample

competes for antibody binding sites with OC coated on the stripwell. A rabbit anti-mouse

IgG antibody conjugated to alkaline phosphatase is added and the reaction is detected with

the substrate, p-nitrophenyl phosphate. Color developed during the incubation of

captured enzyme conjugate and substrate is measured at 405 nm in a microtiter plate

reader. OC values of unknown specimens are calculated from a calibration curve fit with a

4-parameter logistic equation. Values are expressed in ng/mL. 25 pL of serum per well

(assayed in duplicate) is required for determination of OC.



Pyridinoline Crosslinks

Serum pyridinoline crosslinks were measured with Serum Pyd(r) EIA kit

purchased from Metra Biosystems (Mountain View, CA, USA). The EIA kit uses a

microtiter stripwell format utilizing a rabbit monoclonal anti-PYD antibody. PYD in the

sample competes for antibody binding sites with PYD coated on the stripwell. A goat

anti-rabbit IgG antibody conjugated to alkaline phosphatase is added and the reaction is

detected with the substrate, p-nitrophenyl phosphate. Color developed during the

incubation of captured enzyme conjugate and substrate is measured at 405 nm in a









microtiter plate reader. PYD values of unknown specimens are calculated from a

calibration curve fit with a 4-parameter logistic equation. Values are expressed in nmol/L.

25 pL of serum per well (assayed in duplicate) is required for determination of serum

PYD.



Biochemical Indicators of Oxidative Stress

Lipid Peroxidation Measurements

Malondialdehyde levels were determined spectrophotometrically using the

thiobarbituric acid-reactive substances (TBARS) method previously described (Uchiyama

and Mihara, 1978). The agent 1,1,3,3-tetraethoxypropane was used as the standard for

this assay. Samples were performed in duplicate.

Lipid hydroperoxides were quantified using the ferrous oxidation/xylenol orange

technique previously reported (Hermes-Lima et al. 1995). Cumene hydroperoxide was

used as the standard for this assay. All samples were performed in triplicate. In our

laboratory, the coefficients of variation for the TBARS and lipid hydroperoxide assays are

~3 and 4 percent, respectively.



Oxidative Challenges in vitro

To investigate the relationship between obesity and myocardial antioxidant

capacity, the serum was subjected to a series of several different ROS-generating systems.

Serum aliquots were incubated at a concentration of 7 mg protein/ml in the presence of an

ROS generating system. Following each challenge, the aliquots were analyzed for lipid

peroxidation using the technique of Uchiyama and Mihara (1978).










Xanthine-Xanthine Oxidase System (Superoxide Generator).

Superoxide radicals were generated by the reactions involved in a xanthine-

xanthine oxidase system similar to the technique described by Reid et al. (1992). One ml

of 1 mM xanthine and 0.1 IU xanthine oxidase were added to a 1 ml aliquot of serum and

incubated at 37C for 15 min.



Hydrogen Peroxide System

One ml of hydrogen peroxide (100 mM) was added directly to a one ml aliquot of

serum and incubated at 37C for 15 min according to the method of Scott et al. (1987).



Ferric Chloride System (Hydroxyl Generator)

Hydroxyl radicals were produced in the serum by adding 0.1 mM ferric chloride

(FeCI3). The choice of these particular concentrations is based on the work ofBernier et

al. (1986).



Statistical Analyses

Statistical analyses were performed using the Statistical Package for the Social

Sciences (SPSS) software (version 9.0). Experimental analysis was performed with a3 x 2

repeated-measures analysis of variance (ANOVA) model to determine differences within

and between groups over time. If a significant (group x time) interaction was found, the

appropriate post-hoc procedures were applied. The post-hoc procedure used for this

investigation was a one-way ANOVA with a Scheff6 post-hoc test to determine if and







49

where there was a difference between the group means. Although no statistical differences

were observed between groups at study entry, an analysis of covariance (ANCOVA) was

performed on outcome variables at conclusion of the study. When the ANCOVA revealed

that the covariate significantly contributed to the outcome, then the predicted means

generated by the ANCOVA were analyzed with a one-way ANOVA and a Scheff6 post-

hoc test. Pearson bivariate correlations were performed to examine the degree of

association between variables. A-priori alpha levels were set at 0.05.














CHAPTER 4
RESULTS


Throughout the results section PRE will refer to testing completed prior to the six

month training or control period, and POST will refer to testing completed after the six

month training or control period. In all tables and figures, the values presented are means

plus and minus standard deviation. At study entry, there were no significant differences

between any of the experimental groups. As a further precaution against the influence of

any pre-training differences, ANCOVAs were performed on all outcome variables.



Subject Characteristics


The characteristics for the participants in this study are presented in Table 4.1.

The groups did not significantly differ with respect to any of the variables listed (p>0.05).

Correlation between pre-training percent body fat measured by skinfold and DXA was

0.86 (p<0.01) with no significant difference between methods. Correlation between post-

training percent body fat measured by skinfold and DXA was 0.91 (p<0.01) with no

significant difference between methods.









Table 4.1. Subject Characteristics


VARIABLES CON (n=16) LEX (n=24) HEX (n=22)


PRE POST PRE POST PRE POST

AGE
AGE 71.04.7 67.66.3 66.66.7
(yrs.)

HEIGHT
169.910 167.211.5 167.19.7
(cm)

WEIGHT
WEHT 73.113.8 71.014.3 77.419.3 74.416.5 74.114.8 74.815
(kg)

SKINFOLD
SKFATLD 30.37.5 28.97.4 30.96.0 29.05.1 32.07.8 29.97.8
O/oFAT

DXA %FAT
33.57.4 34.47.2 34.18.9 34.18.4 35.98.6 36.29.0


FAT FREE
FAT FREE 46.510.5 46.010.6 50.514.6 48.713.3 47.712 47.912
MASS (kg)
Values are mean SD. CON = control group, LEX = low-intensity group, HEX = high-
intensity group. DXA = dual energy x-ray absorptiometry









Aerobic Endurance

Oxygen Consumption

Values for peak oxygen consumption (VOg) are presented in Table 4.2. The

absolute and percent changes for V04. are shown in Figures 1 and 2, respectively. As

shown in Figure 1, both the LEX and HEX groups significantly increased VOpc during

the six months of resistance exercise (p<0.05). However, the CON group did not change

during the control period. Peak oxygen consumption increased 23.5% and 20.1% for the

LEX and HEX groups, respectively (Figure2.), which was significantly greater than the

percent change for the CON group (p<0.05).



Treadmill Time to Exhaustion

Treadmill time to exhaustion during the graded exercise test is presented in Table

4.2 and figures 3 and 4. The CON, LEX, and HEX groups increased treadmill time by

6.2%, 26.4% and 23.3%, respectively. However, only the LEX and HEX groups

significantly increased their treadmill time from PRE to POST (p<0.05).



Time to Ascend One Flight of Stairs

The stairs used for this test consisted of 22 steps which had to be completed by

touching every step and not holding the railing. Climb data can be found in Table 4.4, and

Figures 4 and 5. Both the LEX and HEX groups significantly decreased the time

necessary to ascend one flight of stairs following training (p<0.05). The LEX and HEX

groups decreased stair time by 7.3 and 5.8 percent, respectively. However, only the







53

Table 4.2. Comparison of Peak Oxygen Consumption and Treadmill Time to Exhaustion
br the CONIEXand HEX groups Daring a Graded Exercise Test


Values are mean & SD. *p<0.05 vs PR
'
E, *p<0.05 vs CON. +p<0.05 vs. CON (ANCOVA)
CON= control group, LEX = low-intensity group, HEX = high-intensity group. TREADMILL =
treadmill time to exhaustion during GXT.


VARIABLES CON LEX HEX


PRE POST PRE POST PRE POST


(m.kg".lmin) 22.63.4 22.43.4 20.243 24.74.8* 20.96.1 24.45.8*

V02.k
(O ) -0.412.0 23.514.1** 20.123.7"*

T L 11.52.5 12.112.5 11.212.3 14.03.1 12.23.4 15.04.9*+
(n)114 26.43.7 23.33.1
S 1U ~ 6.211.4 26.423.7-* 23.323.1









percent change from pre- to post-training in the LEX group was significantly different

than the CON group (p<0.05).



Changes in Muscular Strength

Chest Press

Muscular strength were determined by determining the maximum amount of

weight that could be lifted for one repetition with good form (lRM). Chest press strength

adaptations to the six months of training are displayed in Table 4.3. The absolute IRM

values, 1RM normalized for fat free mass (relative), and percent changes in IRM strength

from pre- to post-training are shown in Figures 7, 8, and 9, respectively. Both the LEX

and HEX groups, but not CON, increased absolute and relative IRM strength significantly

from pre- to post-training (p<0.05).



Leg Press

Leg press strength adaptations to the six months of training are displayed in Table

4.3 and Figures 10, 11, and 12. Both the LEX and HEX groups, but not CON, increased

absolute and relative IRM strength significantly from PRE to POST-training (p<0.05).



Leg Curl

Leg curl strength adaptations to the six months of training are displayed in Table

4.3 and Figures 13, 14 and 15. Both the LEX and HEX groups, but not CON, increased

absolute and relative IRM strength significantly from pre- to post-training (p<0.05).









Biceps Curl

Biceps curl strength adaptations to the six months of training are displayed in

Table 4.3 and Figures 16, 17, and 18. Both the LEX and HEX groups, but not CON,

increased absolute and relative 1RM strength significantly from pre- to post-training

(p<0.05).



Seated Row

Seated row strength adaptations to the six months of training are displayed in

Table 4.3 and Figures 19, 20, and 21. Both the LEX and HEX groups, but not CON,

increased absolute and relative IRM strength significantly from pre- to post-training

(p<0.05).



Overhead Press

Overhead press strength adaptations to the six months of training are displayed in

Table 4.3 and Figures 22, 23, and 24. Both the LEX and HEX groups increased absolute

and relative IRM strength significantly from pre- to post-training (p<0.05).



Triceps Dip

Triceps dip strength adaptations to the six months of training are displayed in

Table 4.3 and Figures 25, 26, and 27. Both the LEX and HEX groups, but not CON,

increased absolute and relative 1RM strength significantly from pre- to post-training

(p<0.05).










Table 4.3. Comparison of Changes in Muscular Strength for the CON, LEX, and HEX
Groups Following Six Months of Resistance Training.
CON LEX HEX
PRE POST PRE POST PRE POST
CP IRM 191.792.3 184.990.0 223.7116.2 258.8129.8*+ 254.3141 287.7157.3*+
CPREL 4.11.1 3.91.2 4.11.4 4.91.3* 5.01.6 5.61.7* **+
CP%A -1.219.9 17.513.5"* 16.016.6**
LP IRM 329.178.4 329.282.3 401.0120.1 469.1158.6* **+ 375.4171 469.1196.6"
LPREL 7.01.1 7.22.2 7.92.2 9.32.0*" + 7.71.7 9.72.3 **+
LP %A 1.522.3 15.715.9 27.618.3"*
LC IRM 180.355.2 179.259.2 174.559.4 217.173.8* 209.583.4 246.8108.7*
LC REL 3.810.6 3.80.7 3.50.7 4.4.4+ 4.31 5.01l.1 +
LC %A -0.710 25.313.4** 17.39.5"*
BC IRM 113.848.3 107.1144.6 118.449.8 138.858.2* 114.444.9 143.965.8*
BC REL 2.30.7 2.30.6 2.20.6 2.70.5* 2.40.5 3.00.7* **+
BC %A -3.816.2 17.89.8** 24.614.3"*
SR IRM 252.692.9 268.0101.4 318.9125.5 276.2136.9*+ 228.8109 376.5140*+
SRREL 5.4l1.0 5.81.1 591.3 7.21.10 **+ 6.31.0 7.61.2" **+
SR%A 6.516.4 19.211.4"* 22.115.9**
OP IRM 176.173.9 169.578.5 215.398.4 251.6110.6* 220.5113 257.1135.4*
OPREL 3.71.0 3.61.1 3.91.1 4.81.0*+ 4.51.3 5.21.5* "+
OP %A -3.618.0 18.811.7** 16.610.0"
TD IRM 219.869.4 217.767.7 263.295.7 310.5111" + 265.299.9 307.9123 **
TDREL 4.70.6 4.80.6 4.80.9 5.90.8* **+ 5.41.0 6.21.2* **+
TD%A -0.75.8 18.59** 16.110.0"*
LE IRM 234.0175.4 222.974.7 276.2102 305.6114* 298.1123 347.1167"
LE REL 5.01.0 4.90.9 5.31.0 5.81.0* 5.91.3 6.8.91 **+
LE4%A -4.68 10.87.3** 14.611.8"*
TS IRM 1697537 1678535 1719696 2029818* 1909850 22631078*
TS REL 36.04.4 36.06.6 32.29.2 38.58.8* 38.58.9 45.312.0"+
TS %A -1.16.3 17.29.7"* 17.87.8"*
Values are mean SD. *p<0.05 vs PRE, **p<0.05 vs CON. +p<0.05 vs CON (ANCOVA)CON
= control group, LEX = low-intensity group, HEX = high-intensity group. CP = chest press, LP =
leg press, LC = leg curl, BC = biceps curl, SR= seated row, OP = overhead press, TD = triceps
dip, LE = leg extension. TS = total strength. IRM= one repetition maximum. REL = relative
change (Nm/kg FFM), %A = percent change from PRE to POST.









Leg Extension

Leg extension strength adaptations to the six months of training are displayed in

Table 4.3 and Figures 28, 29, and 30. Both the LEX and HEX groups, but not CON,

increased absolute 1RM strength significantly from pre- to post-training (p<0.05).



Total Strength

The result for total strength was computed by summing the 1RM values for the

chest press, leg press, leg curl, biceps curl, seated row, overhead press, triceps dip, and leg

extension. The means and standard deviations for total strength for each of the three

experimental groups can be found in Table 4.3. The results for total strength expressed in

absolute numbers (Nm), relative to fat free mass (Nm/kg FFM), and as percent change

from pre- to post-training are shown in Figures 31, 32, and 33, respectively. Both the

LEX and HEX groups, but not CON, significantly increased absolute and relative force

output from pre to post-training (p<0.05).



Muscular Endurance

Chest Press

Chest press endurance data can be found in Table 4.4. The results for number of

repetitions and percent change from pre- to post-training for chest press endurance are

shown in Figures 34 and 35, respectively. Both the LEX and HEX groups, but not CON,

significantly increased the number of repetitions performed from pre- to post-training

(p<0.05).










Leg Press

Leg press endurance data can be found in Table 4.4. The results for number of

repetitions and percent change from pre- to post-training for chest press endurance are

shown in Figures 36 and 37, respectively. Both the LEX and HEX groups, but not CON,

significantly increased the number of repetitions performed from pre- to post-training

(p<0.05).


Table 4.4. Comparison of Stair Climbing Time, Chest Press and Leg Press Endurance for
the CON LEX, and HEX Groups Following Six Months of Resistance Training

CON LEX HEX


PRE POST PRE POST PRE POST


STAIRS (s) 9.11.2 9.01.0 9.41.7 8.691.4* 8.231.8 7.771.7+


STAIRS
S -0.5816.7 -7.316.4* -5.797.56
OKA


CHET 17.65.8 16.95.3 16.94.5 28.67.6* **+ 17.18.7 27.412 **+
(reps)

CHEST
CHEST -0.0532 75.547.4** 68.035.2**



LEG(reps) 32.216.3 29.418 26.39.4 45.020*+ 25.113.4 48.324.5*+


LEG %A -5.043.7 79.210.6" 10594.3**

Values are mean SD. *p<0.05 vs PRE, **p<0.05 vs CON. +p<0.05 vs CON (ANCOVA)
CON = control group, LEX = low-intensity group, HEX = high-intensity group. STAIRS = time to
ascend one flight of stairs. CHEST = chest press endurance. LEG = leg press endurance.









Lumbar Extension Strength

Lumbar extension strength was measured isometrically at 7 different angles of

lumbar flexion and is expressed in Newton meters (Nm). The seven angles used for this

test were 0, 12, 24, 36, 48, 60, and 72 degrees of lumbar flexion.



0 of Lumbar Flexion

Lumbar extension strength values at 00 of lumbar flexion can be found in Table 4.5

and Figures 38, 39, and40. Both the LEX and HEX groups, but not CON, significantly

increased both absolute and relative force output from pre- to post-training (p<0.05).



12 of Lumbar Flexion

Lumbar extension strength values at 12* of lumbar flexion can be found in Table

4.5 and Figures 38, 39, and 40. Both the LEX and HEX groups, but not CON,

significantly increased both absolute and relative force output from pre- to post-training

(p<0.05).



24 of Lumbar Flexion

Lumbar extension strength values at 24' of lumbar flexion can be found in Table

4.5 and Figures 38, 39, and40. Both the LEX and HEX groups, but not CON,

significantly increased both absolute and relative force output from pre- to post-training

(p<0.05).








360 of Lumbar Flexion

Lumbar extension strength data at 360 of lumbar flexion can be found in Table 4.5

and Figures 38, 39, and40. Both the LEX and HEX groups, but not CON, significantly

increased both absolute and relative force output from pre- to post-training (p<0.05).



48 of Lumbar Flexion

Lumbar extension strength data at 480 of lumbar flexion can be found in Table 4.5

and Figures 38, 39, and 40. Both the LEX and HEX groups, but not CON, significantly

increased both absolute and relative force output from pre- to post-training (p<0.05).



600 of Lumbar Flexion

Lumbar extension strength data at 60* of lumbar flexion can be found in Table 4.5

and Figures 38, 39, and40. Both the LEX and HEX groups, but not CON, significantly

increased both absolute and relative force output from pre- to post-training (p<0.05).



72' of Lumbar Flexion

Lumbar extension strength data at 720 of lumbar flexion can be found in Table 4.5

and Figures 38, 39, and40. Both the LEX and HEX groups, but not CON, significantly

increased both absolute and relative force output from pre to post-training (p<0.05).








61

Table 4.5. Comparison of Changes in Lumbar Extension Strength for the CON, LEX, and
HEX Groups Following Six Month of Resistance Training.
ANGLES CON LEX HEX

PRE POST PRE POST PRE POST
O0ABS 137t76 104191 10369 16575* 9374 172107'

0OREL 2.61.11 1.841.3 2.21.6 3.61.2'**+ 1.81.1 3.41.31-*+

0'%A -33.339 141.4A184" 130.3114"*

12ABS 185183 1601102 13571 20779* 138106 229118*

12"REL 3.71 3.11.3 2.71.4 4.41.2*+ 2.71.5 4.61.4* *+

12'%A -13.940 8787"* 1121110"*

24'ABS 217104 19188 14685 23884* 187115 254125*

240 REL 4.31.1 3.81 2.91.6 5.01.0" *+ 3.81.6 521.3 **+

24% A -10124 136213" 5766

36'ABS 235108 2181104 175102 25994* 207114 270125*

36 REL 4.61.1 4.31.1 3.41.6 5.31.0*+ 4.21.5 5.51.3 **+

36% A -5.8120 76.564*" 40.432**

48'ABS 237100 226107 201103 27492* 233134 273134*

48 REL 4.71 4.51.1 3.71.5 5.510.8*+ 4.71.7 5.51.4"+

48'%A -5.716 5341** 2734

60'ABS 240184 259113 20199 26787* 249t138 278134*

60* REL 4.810.9 5.21.2 3.911.5 5.60.8* 5.11.6 5.71.3*

60 % A 7.019 4837"* 18122

72'ABS 24175 249196 19789 26283* 254125 289138*

72'REL 4.911.9 5.12.4 4.21.7 5.71.0* 5.31.3 6.01.2'

72% A -7.1140 45.3138"* 1717

TSLB ABS 1342400 1245550 1100494 16131495' 1364796 1772887*

TSLB REL 28.214.7 25.816.3 22.39.2 34.36.3*+ 27.59.7 35.98.8' **+

TSLB% A -8.0123 62.644"* 39.530.3**
Values are mean SD. *p<0.05 vs PRE, **p<0.05 vs CON. tp<0.05 vs HEX. +p<0.05 vs. CON
(ANCOVA). CON = control group, LEX = low-intensity group, HEX = high-intensity group.
TSLB = total lumbar strength. REL = relative change (Nm/kg FFM), %A = percent change from
PRE to POST. ABS= absolute value (Nm)








Total Lumbar Extension Strength

The result for total lumbar extension strength was computed by summing the peak

force generated for each of the seven angles tested. Total lumbar strength data for each of

the three experimental groups can be found in Table 4.5 and Figures 41, 42, and 43. Both

the LEX and HEX groups, but not CON, significantly increased absolute and relative

force output from pre to post-training (p<0.05).



Bone Mineral Density

Total Body Bone Mineral Density

The means and standard deviations for total body bone mineral density (BMD) are

shown in Table 4.6. The results for absolute BMD and percent change from pre to post-

training can be found in Figures 44 and 45, respectively. There were no significant

differences either between groups or from pre to post-training (p>0.05).



Femoral Neck Bone Mineral Density

Femoral neck bone mineral density data are shown in Table 4.6 and Figures 46 and

47. The HEX group significantly increased BMD of the Femur Neck from pre to post-

training (p<0.05).



Anterior/Posterior Lumbar Spine Bone Mineral Density

The means and standard deviations for anterior/posterior (AP) lumbar spine bone

mineral density are shown in Table 4.6 and Figures 48 and 49. There were no significant








differences between groups at study entry and AP BMD did not change (p>0.05) after 6

months of training or control period.



Lateral Lumbar Spine Bone Mineral Density

Lateral lumbar spine bone mineral density data are shown in Table 4.6 and Figures

50 and 51. There were no significant differences between groups at study entry and lateral

lumbar spine BMD did not change (p>0.05) after 6 months of training or control period.



Ward's Triangle Bone Mineral Density

Ward's triangle bone mineral density data are shown in Table 4.6 and Figures 52

and 53. There were no significant differences between groups at study entry and Ward's

triangle BMD did not change (p>0.05) after 6 months of training or control period.



Correlations Between Physiological Performance Variables and Muscular Strength

Correlation coefficients relating VO2p, stair climbing time (STAIRS), and

treadmill time to exhaustion (TREADMILL) to leg press 1RM (LP 1RM), leg press

endurance (LP END), leg curl 1RM (LC IRM), leg extension (LE IRM), total strength

(TOTAL STR.), and training volume (TRAINING VOL) can be found in Tables 4.7 and

4.8. Training volume was calculated by multiplying the training weights for each of the

exercises performed on the last day of training times the number of repetitions performed.










The correlation coefficients for absolute and percent changes in VOP,

to changes in muscular strength and endurance can be found in Tables 4.7 and 4.8,

respectively. As shown in Table 4.7, absolute VO4,pk is significantly correlated (p<0.05)

to all muscular strength variables listed except for LP END (p<0.05). This indicates that

resistance training is related to, and can lead to increases in VOp The results from

Table 4.8 show that percent changes in muscular strength are not related to percent

changes in VO. This indicates that the magnitude of change for the two variables may

not be related. In other words, a 25% increase in leg press 1RM may not correspond to a

25% increase in VO However, it is important to note that increased strength is

associated with increased aerobic capacity.



Treadmill Time to Exhaustion

The correlation coefficients for absolute and percent changes in treadmill time to

exhaustion during the GXT and changes in muscular strength and endurance can be found

in Tables 4.7 and 4.8, respectively. As shown in Table 4.7, absolute TREADMILL is

significantly (p<0.05) correlated to all muscular strength variables except for LP IRM and

TRAINING VOL. (p<0.05). These results indicate that resistance training can increase

TREADMILL during a GXT in the absence of endurance training. It is interesting to

notethat LE was the most highly correlated strength variable to treadmill time, while LP

IRM was not significantly correlated at all, even though both are quadriceps exercises.









Table 4.6. Changes in Bone Mineral Density for the CON, LEX, and HEX Groups
Following Six Months of Resistance Training or Control Period.

SITE CON LEX HEX

PRE POST PRE POST PRE POST

TOTAL BMD
(g/cm2) 1.1960.1 1.1870.1 1.1950.1 1.1890.1 1.1920.1 1.1820.1

TOTAL %A -0.731.9 -0.422.1 -0.211.6

FEMNK
(g/cm2) 0.8630.1 0.8480.1 0.8930.2 0.90.18 0.8520.1 0.8690.1*

FEMNK/%A -1.594.89 0.685.57 1.963.33

APSPINE
(g/cm2) 1.2280.2 1.2220.2 1.1860.2 1.1820.2 1.1970.2 1.1880.2

APSPINE %A -.02514.1 -0.4643 -0.9583.5

LTSPN
(g/cm2) 0.6450.2 0.6510.2 0.7150.3 0.720.2 0.6940.3 0.6740.2
LATSPINE
%A*& 0.64413.1 3.2216.91.11715.6
%Ao 1.11715.6
WARD'S
(g/cm2) 0.690.1 0.6760.2 0.7430.2 0.7330.2 0.6770.1 0.6760.1

WARD'S %A -1.948.3 -0.746.4 -0.176.7


vuaues are mean i a. "p group, HEX = high-intensity group. TOTAL = total body. FEMNK = femoral neck.
APSPINE = anterior/posterior spine. LTSPN = lateral spine. WARD'S = Ward's triangle.
%A = percent change from PRE to POST.









Table 4.7. Correlations Between Absolute VOa.k, Treadmill Time, and Stair Time and
Select Strength Measures. r Values are Shown Followed by Significance Value in
Parentheses


VO .k

STAIRS

TREADMILL

LP IRM

LP END

LC 1RM

LE IRM

TOTAL STR.

TRAINING VOL.


VO2,

1.0 (0.00)**

-0.53(0.00)**

0.72(0.00)*

0.45(0.00)**

0.03(0.85)

0.42(0.01)**

0.54(0.00)**

0.40(0.01)**

0.46(0.01)**


STAIRS

-0.53(0.00)**

1.0 (0.00)**

-0.34(0.02)*

-0.73(0.00)**

-0.09(0.6)

-0.67(0.00)**

-0.78(0.00)**

-0.64(0.00)**

-0.54(0.00)**


TREADMILL

0.72(0.00)*

-0.34(0.02)*

1.0 (0.00)**

0.28(0.07)

0.37(0.014)*

0.29(0.054)

0.43(0.01)**

0.31(0.04)*

0.24(0.19)


* correlation significant at p<0.05, **correlation significant at p<0.01. VO k = maximal
oxygen consumption during graded exercise test (GXT). TREADMILL = time to
exhaustion during GXT. STAIRS = time to ascend one flight of stairs. LP 1RM = leg
press 1RM. LP END = leg press endurance. LC IRM = leg curl IRM. LE 1RM = leg
extension 1RM. TOTAL STR. = total strength. TRAINING VOL. = training volume.


--








Table 4.8. Correlations Between Percent Changes in VO k, Treadmill Time, and Stair
Time and Select Strength Measures. r Values are Shown Followed by Significance Value
in Parentheses
VOp STAIRS TREADMILL

VO., 1.0 (0.00)** -0.19(0.22) 0.26(0.09)

STAIRS -0.19(0.22) 1.0 (0.00)** -0.17(0.24)

TREADMILL 0.26(0.09) -0.17(0.24) 1.0 (0.00)**

LP IRM 0.21(0.20) -0.20(0.18) 0.01(0.93)

LPEND 0.13(0.41) -0.31(0.03)* 0.25(0.11)

LC IRM 0.36(0.02)* -0.21(0.15) 0.21(0.17)

LE IRM 0.06(0.72) -0.54(0.00)** 0.25(0.12)

TOTAL STR. 0.23(0.14) -0.40(0.00)** 0.17(0.25)
* correlation significant at p<0.05, **correlation significant at p<0.01. VOzp* = maximal
oxygen consumption during graded exercise test (GXT). TREADMILL = time to
exhaustion during GXT. STAIRS = time to ascend one flight of stairs. LP 1RM = leg
press 1RM. LP END = leg press endurance. LC IRM = leg curl 1RM. LE 1RM = leg
extension IRM. TOTAL STR. = total strength.








Stair Climbing Time

The correlation coefficients for absolute and percent changes in STAIRS to

changes in muscular strength and endurance can be found in Tables 4.7 and 4.8,

respectively. As shown in Table 4.7, absolute STAIRS is significantly (p<0.05) correlated

to all strength variables except for LP END (p>0.05). The correlations are negative

values indicating an inverse correlation. This indicates that as muscular strength increases,

the time necessary to ascend one flight of stairs decreases. STAIRS was also significantly

correlated to the other physiological performance variables of TREADMILL and VO*.k.

Percent change in STAIRS.is significantly (p<0.05) correlated to all muscular strength

variables except for LC IRM (p>0.05). These correlations are also inverse indicators that

the percent increase in muscular strength and endurance is related to a percent decrease in

stair climbing time.



Correlations Between Physiological Performance Variables and Bone Mineral Density

Correlation coefficients relating total body (TOTAL), femoral neck (FEMNK),

Ward's triangle (WARD'S), anterior/posterior lumbar spine (AP SPINE), and lateral

lumbar spine (LAT SPINE) to leg press IRM (LP IRM), overhead press (OP IRM), total

strength (TOTAL STR.), and total lumbar extension strength (TOTAL LMB) can be

found in Tables 4.9 and 4.10.



Total Body

The correlation coefficients for absolute and percent changes in TOTAL to

changes in muscular strength can be found in Tables 4.9 and 4.10, respectively. As shown









in Table 4.9, absolute TOTAL was significantly (p<0.05) correlated to all strength

variables. This indicates that greater muscular strength is associated with greater TOTAL

bone mineral density.



Femoral Neck

The correlation coefficients for absolute and percent changes in FEMNK

to changes in muscular strength can be found in Tables 4.9 and 4.10, respectively. As

shown in Table 4.9, absolute FEMNK was significantly (p<0.05) correlated to all strength

variables except TOTAL LMB. The lack of a correlation between TOTAL LMB and

FEMNK was not surprising because the MedX lumbar extension machine is designed to

isolate the lumbar spine and not involve any other musculature.



Ward's Triangle

The correlation coefficients for absolute and percent changes in WARD'S

to changes in muscular strength can be found in Tables 4.9 and 4.10, respectively. As

shown in Table 4.9, absolute WARD'S was not significantly correlated to any of the

strength variables (p>0.05). This indicates that greater muscular strength is not associated

with greater WARD'S bone mineral density.



Anterior/Posterior Lumbar Spine

The correlation coefficients for absolute and percent changes in AP SPINE

to changes in muscular strength can be found in Tables 4.9 and 4.10, respectively. As

shown in Table 4.9, absolute AP SPINE was significantly (p<0.05) correlated to all







70
strength variables. This indicates that greater muscular strength is associated with greater

AP SPINE bone mineral density,



Lateral Lumbar Spine

The correlation coefficients for absolute and percent changes in LAT SPINE

to changes in muscular strength can be found in Tables 4.9 and 4.10, respectively. As

shown in Table 4.9, absolute LAT SPINE was significantly (p<0.05) correlated to all

strength variables. This indicates that greater muscular strength is associated with greater

LAT SPINE bone mineral density.





Table 4.9. Correlations Between Absolute Changes in Bone Mineral Density and Select
Strength Measures. r Values are Shown Followed by Significance Value in Parentheses

SITE TOTAL STR TOTAL LMB LP 1RM OP 1RM

TOTAL 0.58(0.00)** 0.48(0.00)** 0.60(0.00)** 0.57(0.00)**

FEMNK 0.29(0.04)* 0.18(0.28) 0.29(0.05)* 0.30(0.03)*

WARD'S .07(0.61) 0.05(0.78) 0.22(0.13) 0.16(0.26)

AP SPINE 0.38(0.01)** 0.33(0.05)* 0.43(0.00)** 0.41(0.00)**

LAT SPINE 0.60(0.00)** 0.44(0.01)** 0.61(0.00)** 0.63(0.00)**
* correlation significant at p<0.05, **correlation significant at p<0.01. LP IRM = leg
press IRM. OP IRM = overhead press IRM. TOTAL LMB = total lumbar strength.
TOTAL STR. = total strength. TOTAL = total body. FEMNK = femoral neck.
WARD'S = Ward's triangle. AP SPINE = anterior/posterior spine. LAT SPINE = lateral
spine.









Biochemical Analyses


TBARS

Thiobarbituric acid-reactive substances (TBARS) data are shown in Table 4.11.

The results for absolute TBARS and percent change from pre to post-training can be

found in Figures 62 and 63, respectively. The level of peak exercise TBARS, and

therefore lipid peroxidation was lower in the LEX group compared to the CON group

following the post-training GXT (p<0.05). Also, the percent change from pre- to post-

GXT for the LEX group following the training period was significantly lower than those

of the HEX and CON groups (p<0.05). These results suggest that the exercise training

imparted some measure of protection from oxidative stress on the people in the LEX

group. The results for the in vitro oxidative stress challenges are presented in Table 4.11.

The results indicate that the post-training FeCI3 TBARS response of the HEX group was

significantly greater than those of the LEX and CON groups (p<0.05). However, the

TBARS response following the H202 challenge was lower for the LEX group compared

to the CON group (p<0.05).



Lipid Hydroperoxides

Lipid hydroperoxides values can be found in Table 4.11. The results for lipid

hydroperoxides are shown in figure 64. All groups (CON,LEX, HEX) significantly

increased lipid hydroperoxide levels at peak exercise at study entry (p<0.05). Following

the training or control period, only the CON group showed a significant increase in lipid

hydroperoxides and the the levels for the LEX and HEX groups were significantly lower








than that of the CON group (p<0.05). The percent increase in lipid hydroperoxides

immediately following the post-training GXT was significantly lower for the LEX group

compared to the CON and HEX groups (p<0.05).



Serum Osteocalcin

Serum osteocalcin values are shown in Table 4.12 and Figures 65 and 66. Both the

LEX and HEX groups, but not CON, significantly increased osteocalcin levels from pre to

post-training (p<0.05).



Serum Bone-Specific Alkaline Phosphatase

Serum bone-specific alkaline phosphatase (BAP) data are shown in Table 4.12 and

Figures 67 and 68. The HEX group significantly increased BAP levels from pre to post-

training (p<0.05).



Serum Pyridinoline Crosslinks

Serum pyridinoline crosslinks (PYD) values are shown in Table 4.12 and Figures 69

and 70. None of the groups significantly changed PYD from pre- to post-training

(p






73
Table 4.10. Correlations Between Percent Changes in Bone Mineral Density and Select
Strength Measures. r Values are Shown Followed by Significance Value in Parentheses

SITE TOTAL STR TOTAL LMB LP 1RM OP IRM

TOTAL 0.13(0.36) 0.04(0.81) -0.11(0.45) 0.04(0.80)

FEMNK 0.33(0.02)* -0.09(0.61) 0.25(0.09) 0.23(0.11)

WARD'S 0.15(0.28) 0.28(0.09) 0.01(0.94) 0.18(0.22)

AP SPINE 0.01(0.94)** 0.13(0.45) -0.11(0.47) -0.02(0.87)

LAT SPINE 0.10(0.48) 0.31(0.06) 0.18(0.23) 0.15(0.29)

* correlation significant at p<0.05, **correlation significant at p<0.01. LP IRM = leg
press IRM. OP 1RM = overhead press 1RM. TOTAL LMB = total lumbar strength.
TOTAL STR. = total strength. TOTAL = total body. FEMNK = femoral neck.
WARD'S = Ward's triangle. AP SPINE = anterior/posterior spine. LAT SPINE = lateral
spine.










Table 4.11. Comparison of Changes in Markers of Oxidative Stress for the CON, LEX,
and HEX Groups Following Six Months of Resistance Trainin.
MARKER CON LEX HEX

PRE POST PRE POST PRE POST
TBARS
PRE-XT 0.2340.05 0.2220.05 0.2110.04 0.2070.03 0.240.0.07 0.2110.03
(nmol/mln

%A -4.8511.2 -0.1216.1 -7.8121.6

TBARS
POST- 0.2510.06 0.2540.07 0.2220.06 0.2100.04"* 0.2850.12 0.231t06


%A 1.8511.5 -2.5217.1 -11.628.2

%A PRE-/
POST- 7.116.4 15.924.8 5.113.7 2.414.4"* 20.3141.5 9.9121.8
GXT
3 0.2830.04 0.2790.05 0.2910.06 0.2880.05 0.3170.04 0.340.04**

XO
S 0.2250.06 0.2590.11 0.2530.11 0.2660.11 0.2710.12 0.2350.04
(nmo-ml)
H202
o2 0.5540.36 0.7110.37 0.4330.28 0.4690.25** 0.5790.46 0.678i0.37
(nmolml)
LPD-HPX
L 2.330.62 2.520.56 2.770.78 2.550.72 2.260.64 2.32i0.60"*


%A 12.830.3 -1.9138.8 2.8340.4

LPD-HPX
POST- 2.911.16* 3.410.51* 3.300.90* 2.920.76"* 3.020.77 2.870.5**
GXT
%A PRE-/
POST- 22.517.0 39.227.1 20.421.0 16.918.9**l 34.240.4 33.430.1
GXTI III


Values are mean SD. *p<0.05 vs PRE-GXT. **p<0.05 vs. CON (ANCOVA). :p<0.05
HEX vs. LEX (ANCOVA). CON = control group, LEX = low-intensity group, HEX =
high-intensity group.FECL3 = ferric chloride. XO = hypothanine/xanthine oxidase. H202
= hydrogen peroxide. LPD-HPX = lipid hydroperoxides. PRE-GXT = before graded
exercise test.. POST-GXT = post-graded exercise test. %A = percent change from PRE to
POST-training. TBARS = thiobarbituric acid-reactive substances







75



Table 4.12. Comparison of Changes in Markers of Bone Metabolism for the CON, LEX,
and HEX Groups Following Six Months of Resistance Training.
MARKER CON LEX HEX

PRE POST PRE POST PRE POST
OSCAL
(ngO L 12.325.4 13.235.2 10.744.0 13.587.2* 11.945.0 15.577.4-

%A 6.631.7 25.136.8 39.044.6
ALKPHOS
L 21.1410.4 18.884.6 16.625.6 17.545.7 17.866.6 19.157.5*

%A 3.015.9 7.820.7 7.113.3
PYD
(nmol/L) 1.820.8 1.720.6 1.500.7 1.510.6 1.530.7 1.4510.6

%A -1.334.5 11.352.7 -9.966.4

Values are mean SD. *p<0.05 vs PRE. CON = control group, LEX = low-intensity
group, HEX = high-intensity group. OSCAL = serum osteocalcin. ALKPHOS = bone-
specific alkaline phosphatase. PYD = serum pyridinoline crosslinks. %A = percent change
from PRE to POST-training.












35.0


*
30.0 *




25.0




20.0




15.0 -BCON
LEX
EHEX

10.0




5.0




0.0
PRE POST


Figure 1. Absolute peak oxygen consumption (VO2peak) measured
during a graded exercise test before (PRE) and after (POST) six
months of resistance training.
*p<0.05 vs PRE






















35.0 -


25.0 -


HEX


Figure 2. Percent change in peak oxygen consumption (VO2eak) after
six months of resistance training.
+p

15.0


CON


------X













20.0


18.0
*

16.0


14.0


12.0


10.0


8.0


6.0 CON
ELEX
2HEX
4.0


2.0


0.0
PRE POST


Figure 3. Absolute treadmill time during a graded exercise test
measured before (PRE) and after (POST) six months of resistance
training.
*p<0.05 vs PRE











50.0

+
45.0



40.0



35.0



30.0



25.0-



20.0



15.0



10.0



5.0



0.0
CON LEX HEX

Figure 4. Percent change in treadmill time during a graded exercise
test after six months of resistance training.
+p<0.05 vs CON















II


* CON
ELEX
1 HEX


0.0 --


POST


Figure 5. Absolute stair climbing time measured before (PRE) and
after (POST) six months of resistance training.
*p<0.05 vs PRE










CON LEX HEX
0.0



-2.0



-4.0



-6.0



-8.0



-10.0



-12.0



-14.0

+

-16.0





Figure 6. Percent change in stair climbing time after six months of
resistance training.
+p<0.05 vs CON













450.0


400.0

*
350.0


300.0


250.0


200.0

W CON
150.0 LEX
AHEX
12 HEX I

100.0


50.0


0.0
PRE POST


Figure 7. Absolute chest press IRM measured before (PRE) and after
(POST) six months of resistance training.
*p<0.05 vs PRE













8 -



7-

*

6-



5*p<0.05 v. PRE






5 v. CON
3 ELEX
SHEX

2-



1-



0
PRE POST

Figure 8. Relative chest press IRM measured before (PRE) and after
(POST) six months of resistance training.
*p<0,05 vs. PRE
+p<0.05 vs. CON























* CON U LEX

BHEX


Figure 9. Percent change in chest press IRM after six months of
resistance training.
+p<0.05 vs CON


0.0


-10.0




-20.0-




-30.0-












700.0


*+
600.0
*+


500.0



400.0



300.0

M CON
ELEX
200.0- [ HEX



100.0



0.0
PRE POST


Figure 10. Absolute leg press 1RM measured before (PRE) and after
(POST) six months of resistance training.
*p<0.05 vs PRE
+p<0.05 vs. CON














14


*
12




10




8




6 MCON
MLEX
MHEX

4-




2-




0
PRE POST

Figure 11. Relative leg press 1RM measured before (PRE) and after
(POST) six months of resistance training.
*p<0.05 vs. PRE












60.0

+


50.0




40.0




S30.0




20.0




10.0




0.0
CON LEX HEX


Figure 12. Percent change in leg press IRM after six months of
resistance training.
+p<0.05 vs CON











































POST


Figure 13. Absolute leg curl 1RM measured before (PRE) and after
(POST) six months of resistance training.
*p<0.05 vs PRE


350.0



300.0



250.0



200.0



150.0



100.0



50.0



0.0 --


T
T


* CON
MLEX
MHEX























*


7-



6




5-




4"



S3-




2 -




1 -




0 -


POST


Figure 14. Relative leg curl IRM measured before (PRE) and after
(POST) six months of resistance training.
*p<0.05 vs. PRE
+p<0.05 vs. CON
**p<0.05 vs. LEX


* CON
*LEX
BHEX


------ I




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