Muscle glycogen depletion during maximal isokinetic contractions

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Benham, David W.
Costill, David L.
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Thesis (M.A.)
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The intent of this investigation was to determine the effects of contractile velocity on muscle glycogen depletion patterns during maximal isokinetic contractions.Three physically active male subjects performed maximal knee extensions and flexions using the Cybex II. Work was performed with one leg at a contractile volecity of 60 degs./sec. (1.05 rads./sec.) and the other at 300 degs./sec. (5.23 rads./sec.). Histochemical data was collected from muscle samples taken from the vastus lateralis m. of each leg. Gylcogen depletion patterns were later observed from a periodic-acid Schiffs stain (PAS) on the muscle sections. Additional muscle samples were freeze-dried for single fiber evaluation, of glycogen content. Both fast twitch (FT) and slow twitch (ST) muscle fibers were depleted of glycogen equally during each of the contractile velocities. Observations from FAS staining suggest that most of the FT fibers were depleted before the ST fibers. The results of this study indicate that the glycogen depletion pattern is independent of the velocity of contraction. This study also supports previous investigations in suggesting that the intensity of muscular contraction is one of the major determinants of the glycogen depletion pattern.