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James Dowling
02-14-1994, 01:46 AM
Dear BIOMCH-Lers,
I am involved in a research project on muscular fatigue and EMG. We
are trying to explain a phenomenon that is very prevalent in isometric
contractions. When subjects hold a 75% MVC for as long as possible, the
EMG increases to maximal levels before they can no longer
continue. However, when a 30% contraction is maintained, the EMG rises
only to about 70% of the maximum (MVC value) before the subject is unable
to continue. I should also mention that when a maximum twitch via
percutaneous stimulation is imposed on top of the voluntary effort, extra
force is seen even though the subject is at the point of voluntary
failure. We are aware of: Fuglevand, et al. (1993) Impairment of
neuromuscular propagation during human fatiguing contractions at
submaximal forces. J APPL PHYSIOL. 460:549-572 but any other references
or comments from those of you who have experiences with this would be
greatly appreciated.

Sincerely,
Jim Dowling
E-Mail: Dowlingj@Mcmail.McMaster.CA