View Full Version : EMG fatigue measures

07-29-1998, 08:19 AM
Hi, I am posting this message on behalf of a colleague. Any assistance
would be appreciated:

We are interested in examining EMG fatigue measures (median power
frequency) during an isometric contraction of the quadricep muscles of
people who have severe muscle atrophy secondary to immobilization from a
fracture. We will be following these subjects from the point of cast
removal to full strength recovery. After surveying the literature we felt
that a submaximal contraction kept at the same absolute force level would
be best since the maximal force output will vary (likely increase) over
their recovery. Also authors such as Mannion and Dole (Eur J Appl Physiol,
74, 1996, p 411-419) have shown that submax isometric contractions can be
used for EMG fatigue measures.

However, we are wondering:
1) By not using a maximal contraction, could this lead to misinterpretation
of the data since different motor units may be required to reach the
maximal force?
2) Also in our case, by keeping the absolute force value of the contraction
the same over time, the relative percent of the fatiguing contraction from
maximum (submaximal percentage) would actually be decreasing over the
recovery. Could this be a confounding variable when it comes to
interpreting the fatigue measures?

Please reply to me directly and I will post a summary if there are
sufficient replies.

Regards, Janice Eng
__________________________________________________ ____
Janice Eng, PhD, PT
Assistant Professor
School of Rehabilitation Sciences, Faculty of Medicine
University of British Columbia
T325-2211 Wesbrook Mall, Vancouver, BC, Canada, V6T 2B5
Tel: (604)714-4105 Fax: (604)822-7624

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