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Arnel Aguinaldo
11-28-1999, 08:43 PM
To all BIOMCH and ATC subscribers:

I'm currently conducting research on the use of neuromuscular electrical
stimulation (NMES) for therapeutic applications, and I would like to get
feedback on the specific effects of NMES on muscle activity.

Although the effects of NMES have been investigated numerous times in past
studies, there seems to be conflicting views on the overall effectiveness
of NMES as compared to voluntary exercise. During a physiological
contraction, motor units are recruited according to the size principle.
Slow (S), Fast-Fatigue-Resistant (FR), and Fast-Fatigue (FF) units are
recruited respectively as voluntary force increases. During a NMES induced
contraction, however, it is unclear which units are actually being
recruited. Further, the same motor units respond each time NMES is applied.
There does not seem to be a clear explanation to why these responses happen
during NMES so I pose the following questions to the group:

1) Does NMES induced contractions follow the size principle?
2) If not, which motor units are primarily recruited when NMES is applied
and why?
3) If the same units are activated with each stimulation, would muscle
fatigue be more prevalent than it would with physiological contractions?

These questions are important to answer because it would explain how NMES
could be optimized to control the tension levels associated with its
application. A muscle will respond according to the stress imposed upon it.
Thus if NMES can produce higher tensions, then it would result in more
effective strengthening. In a study conducted by Lieber et al (1992), it
was found that muscle strengthening with NMES is just "as effective as
voluntary exercise, provided the tension levels are equivalent." It is
obvious, therefore, that NMES needs to be applied at conditions appropriate
to reach tension levels comparable to voluntary exercise. However, a better
understanding of the physiological responses to NMES is needed in order to
optimize these conditions.

Any feedback on this subject will be greatly appreciated. Thank you.



=======================================
Arnel Aguinaldo, M.A.
Biomechanical Engineer
Athletic Training Intern

San Diego State University
University of California, San Diego
San Diego, CA
email: ala@znet.com
=======================================










To all BIOMCH and ATC subscribers:

I'm currently conducting research on the use of neuromuscular electrical
stimulation (NMES) for therapeutic applications, and I would like to get
feedback on the specific effects of NMES on muscle activity.

Although the effects of NMES have been investigated numerous times in
past studies, there seems to be conflicting views on the overall
effectiveness of NMES as compared to voluntary exercise. During a
physiological contraction, motor units are recruited according to the
size principle. Slow (S), Fast-Fatigue-Resistant (FR), and Fast-Fatigue
(FF) units are recruited respectively as voluntary force increases.
During a NMES induced contraction, however, it is unclear which units are
actually being recruited. Further, the same motor units respond each time
NMES is applied. There does not seem to be a clear explanation to why
these responses happen during NMES so I pose the following questions to
the group:

1) Does NMES induced contractions follow the size principle?
2) If not, which motor units are primarily recruited when NMES is applied
and why?
3) If the same units are activated with each stimulation, would muscle
fatigue be more prevalent than it would with physiological
contractions?

These questions are important to answer because it would explain how NMES
could be optimized to control the tension levels associated with its
application. A muscle will respond according to the stress imposed upon
it. Thus if NMES can produce higher tensions, then it would result in
more effective strengthening. In a study conducted by Lieber et al
(1992), it was found that muscle strengthening with NMES is just "as
effective as voluntary exercise, provided the tension levels are
equivalent."  It is obvious, therefore, that NMES needs to be
applied at conditions appropriate to reach tension levels comparable to
voluntary exercise. However, a better understanding of the physiological
responses to NMES is needed in order to optimize these conditions.

Any feedback on this subject will be greatly appreciated. Thank
you.



=======================================
Arnel Aguinaldo, M.A.
Biomechanical Engineer
Athletic Training Intern

San Diego State University
University of California, San Diego
San Diego, CA
email: ala@znet.com
=======================================