Article

Peripheral fatigue and muscle cooling induce similar effects on sarcolemmal
propagation properties. The aim of the study was to assess the combined effects
of muscle temperature (Tm) manipulation and fatigue on skeletal muscle electrical
and mechanical characteristics during isometric contraction. After maximum
voluntary contraction (MVC) assessment, 16 participants performed brief and
sustained isometric tasks of different intensities in low (Tm(L)), high (Tm(H))
and neutral (Tm(N)) temperature conditions, before and after a fatiguing exercise
(6s on/4s off at 50% MVC, to the point of fatigue). During contraction, the
surface electromyogram (EMG) and force were recorded from the biceps brachii
muscle. The root mean square (RMS) and conduction velocity (CV) were calculated
off-line. After the fatiguing exercise: (i) MVC decreased similarly in all Tm
conditions (P<0.05), while EMG RMS did not change; and (ii) CV decreased to a
further extent in Tm(L) compared to Tm(N) and Tm(H) in all brief and sustained
contractions (P<0.05). The larger CV drop in Tm(L) after fatigue suggests that
Tm(L) and fatigue have a combined and additional effect on sarcolemmal
propagation properties. Despite these changes, force generating capacity was not
affected by Tm manipulation. A compensatory mechanism has been proposed to
explain this phenomenon.
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Langue : ANGLAIS