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Expiratory Muscle Training in Two Healthy Adults
The Increases in expiratory muscle strength through strength training programs can improve pulmonary
function, boost cough magnitude, and augment voice characteristics. Stronger expiratory muscles can push air out
of the lungs with a greater force. This greater force can increase the strength of a cough or raise intensity
while voicing. For people who suffer from diseases that atrophy the expiratory muscles, it may be necessary
to undergo a strength training program to alleviate breathing difficulties. The major expiratory muscles include
the internal and external obliques, the rectus abdominis, the transverse abdominis, and the internal
intercostals. During quiet, or passive breathing, the muscles of exhalation are at rest. Passive exhalation occurs
due to the relaxation of the muscles of inhalation. However, during forced exhalation, the expiratory muscles
become active. Because it is difficult to isolate the expiratory muscles to obtain EMG data, researchers must
assume that the expiratory muscles function in a similar manner as other skeletal muscles. Thus, the
expiratory muscles would respond to a strength training program just as the arm or leg muscles would.
Resistance-based and pressure-threshold techniques are methods by which the expiratory muscles are utilized
in strength training. Resistance based techniques require the individual to exhale through a series of openings
that vary in size. As the openings decrease in size, more force is required to push air through the
obstructed pathway. Pressure-threshold techniques utilize a device with a spring loaded valve. While exhaling,
the person must generate enough pressure to open the valve and maintain a minimum pressure to keep the
valve open through the entire exhalation. Although both methods use different devices, each device requires
and increase in the force generated by the expiratory muscles. The devices provide a type of overload that is
specific to the expiratory muscles. Muscles that receive an overload on a regular basis will respond with increases
in muscle strength and hypertrophy. The increase in muscle strength is partly due to a larger muscle size and
partly due to reactions of the central nervous system. In progressive resistance exercises, the central nervous
system recruits more motor units in the muscle being conditioned, motor neuron firing rates are altered,
the synchronization of motor units during a specific movement pattern is enhanced, and neural inhibition is
lessened. Neural adaptations occur at the onset of training, but level off quickly. However, hypertrophy is slow
to commence, occurs at a slower rate than neural adaptations, and levels off much later. It is important to note
that muscle overloads are followed by adaptation, making it necessary to periodically increase the load.
Mycosed O'Kroy and Coast (1993) performed a resistance-based study with 6 healthy subjects. The trainer was
set weekly at 30% of each subjects' respective MEP. Training lasted for 20 minutes a day. Subjects trained for
four days every week over the course of four weeks. The specific increase in MEP was not reported, however,
O'Kroy and Coast disclosed that the MEP increased 10-20 cm H20, an insignificant amount. In another
resistance based-training study, the MEP of 10 children with hypertonia increased by 69%. Cerny, Panzarella,
and Stathopoulos (1997) trained each subject with the initial resistance set at 2.5 cm H20 and gradually
worked subjects up to a resistance of 7.5 cm H20. The six week training period consisted of 15 minutes of training
for 5 days each week. Due to the increases in expiratory muscle strength, subglottal pressure and vocal intensity
also increased among subjects.
A pressure-threshold training program for 6 healthy subjects showed an average increase in MEP by 25%.
Suzuki, Sato, and Okubo (1995) trained subjects at 30% of their MEP. Subjects trained for 15 minutes twice daily
for 4 weeks. With an increased MEP, subjects showed lowered ratings for perceived breathlessness. In a
similar study, Hoffman-Ruddy, Sapienza, Davenport, Martin and Lehman (2001) trained 8 performers at 75% of
their MEP on a pressure-threshold trainer. The performers trained for 4 sets of 6 breaths five days a week.
The training lasted for a 4 week period. At the end of training, subjects' MEP had increased 84%. A
pressure-threshold study with 40 band students, by Sapienza, Martin, and Davenport, trained subjects at 75%
of their MEP. The students trained for 4 sets of 6 breaths five days a week. The training continued over a period of
2 weeks. Average MEP increased by 47%. Pressure-threshold training with ten multiple sclerosis patients showed
an increase in MEP by 37%. Smeltzer, Lavietes, and Cook (1996) unfortunately did not report the percent of MEP
at which the trainer was set. The patient trained for a period of 12 weeks, performing 3 sets of 15 breaths each.
Self-reports at the end of training showed that patients' voices sounded louder and stronger and cough
reflexes generated more force.
Both resistance-based and pressure-threshold techniques are effective in increasing MEP. In pressure-
threshold studies, higher training loads result in higher increases in MEP. Also, from comparing the studies with
band students and performers, a longer training period will have a larger affect on MEP. Although healthy
subjects showed no significant increase in MEP from resistance-based training, subjects with hypertonia did.
Both resistance-based and pressure-threshold training has been successful with non-healthy populations. It is
difficult to directly compare the two techniques because studies are not consistent in the training load or
the frequency and duration of the training.
Subjects had to meet the following criteria to be included in the study:
18-30 years old
MEP (maximum expiratory pressure) in the normal range for subject's age and sex
able to maintain current level of activity, either aerobic or weightlifting) throughout the duration of
Subjects were excluded from the study according to the following criteria:
chronic and acute cardiac disease, including pulmonary dysfunction or disease, hypertension,
upper respiratory infection, obesity, history of smoking, and acute or chronic vocal disturbances
n=2 Both subjects were female and met all inclusion criteria. Subject A was 21 years old and trained
for 4 weeks. Subject B was 20 years old and trained for 7 weeks.
Prior to and during training, each subjects' MEP was measured using a Fluke 712 30G pressure gauge.
A mouthpiece was connected to the pressure gauge via a length of tubing 15mm in diameter.
Subjects were instructed to inhale maximally then forcefully exhale into the mouthpiece. Nose clips
were used during the procedure, and subjects were directed to maintain a tight seal between their
lips and the mouthpiece during exhalation. After obtaining a series of MEPs within 5% of each other
from each subject, an average MEP was calculated per subject. Each subjects' pressure threshold
trainer was set at 75% of their respective MEPs. Subjects were directed to use the trainer at home 5
days a week. Each training session consisted of 5 sets of 5 breaths. Each breath included a
maximum inhale with an exhale into the trainer. Nose clips were used during the home training
sessions. Subjects were given a training log to keep track of their training sessions. At the end of
each week, subjects returned to the lab to calculate their respective MEPs. The trainers then
were adjusted to reflect 75% of each subjects' MEP.
Detraining began once all training had been completed. Data for detraining was only taken for subject
B, who returned to the lab weekly to have her MEPs taken. Training and detraining MEPs were
measured using the same device.
Breathing exercises with the pressure-threshold trainer were performed for a total of 4 weeks. There
was no detraining period after the initial training was complete. The baseline MEP was 55.0, after 1
week of training, MEP increased to 70.6. By week 2, the MEP was 77.4. By the final week of training,
MEP was 91.3. Over the 4 week training session, Subject A's MEP increased 66% over baseline.
Training on the pressure-threshold device occurred between weeks 1 and 7. Detraining began week
8. Baseline MEP was 78.4. MEP at week 1 was 57.0. There was no MEP taken on week 2 due to illness.
At weeks 3 through 5, MEP was 78.3, 80.8, 88.6, and 91.3 respectively. No MEP was taken on week 7,
the first week of detraining, due to illness. By the second week of detraining, week 8, MEP dropped
to 81.4. MEP for week 9 dropped further to 70.1. MEP for week 10 was 84.9. The final detraining
MEP taken on week 11 was 83.5. During training, weekly through 6, MEP increased 16.5% over baseline.
During detraining, MEP decreased 8.2% from week 6 to week 11. At the end of detraining, week 11,
MEP was still 6.5% over the baseline MEP.
Morphological Subject A shows a consistent, linear improvement in MEP with each week of
training. However, subject B shows a significant drop between week 0 and week 1. This drop could
be due to several factors such as illness or equipment problems. After week 2, subject B's MEP
improves linearly until week 6, but at a slower rate than subject A. Subject B's slower rate
of improvement could be caused by an illness or inconsistent use of the pressure-threshold
trainer. During detraining, subject B shows a decrease in MEPs, as was expected, but experiences a
sharp increase in MEP on week 10. The dramatic increase in MEP during subject B's detraining may
result from a training effect. Subjects may learn to more efficiently use the pressure gauge
that measures MEP, causing an increased MEP reading without actually strengthening the
respiratory muscles. Overall, both subjects experienced an increase in their respective MEPs.
This supports research that pressure-threshold training can increase a person's MEP.
Several significant complications arise when researching the effects of pressure-threshold trainers.
In most studies, subjects are asked to use the trainer regularly at home. Subjects are then given a log
or journal in which to track their training. Consequently, not all subjects use their trainer in the
manner by which they are instructed. Inappropriate use of the pressure-threshold trainer can lead
to unreliable results. Additionally, subjects may not use the trainer for the correct amount of breaths
or sets of breaths as directed by the researcher. Again, this would skew the results of the study.
Illness, a very uncontrollable variable, can decrease a subject's MEP, making training difficult
and uncomfortable. While ill, subjects are instructed to cease training. When sudden stop in
training occurs, muscles quickly begin to atrophy back to baseline. It is important to note that
the equipment used to make MEP measurements can work improperly. Any equipment used should
be calibrated regularly.
Better methodology can correct for subject errors and equipment malfunctions. Of course, more
research is needed on pressure-threshold trainers and their affect on MEP. This is especially
important since pressure-threshold trainers affect MEP in an indirect manner. More research
could pinpoint the muscles directly influenced by pressure-threshold trainers, which would increase
the effectiveness of the devices.
Cerny, F., Panzarella, K., & Stathopoulus, E. (1997). Expiratory muscles conditioning in
hypotonic children with low vocal intensity levels. Journal of Medical Speech- Language Pathology,
Hoffman Ruddy, B., Sapienza, C., Davenport, P., Martin, D., & Lehman, J. (2001). Expiratory pressure
threshold training in "high risk" performers. Poster Session. American Speech-Language-
Hearing Association Annual Convention. New Orleans, Louisiana.
O'kroy, J.A., & Coast, J.R. (1993). Effects of flow and resistive training on respiratory muscle
endurance and strength. Respiration, 60, 279-283.
Smeltzer, S.C., Lavietes, M.H., & Cook, S.D. (1996). Expiratory training in multiple sclerosis. Archives
of physical medicine and rehabilitation, 77, 909-912.
Suzuki, S., Sato, M., & Okubo, T. (1995). Expiratory muscle training and sensation of respiratory
effort during exercise in normal subjects. Thorax, 50, 366-370.
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