Isometric Fatigue Curves in Human Muscle with Normal and Occluded Circulation

Abstract

Fatigue curves for the forearm muscles during sustained isometric contraction were obtained on 24 young men. No difference was found between the curves obtained with and without artificial occlusion of the circulation, down to the point where the exerted force became less than approximately 60 per cent of the maximal strength. Below this critical level, the exerted force continued to diminish under the occluded condition, but leveled off when there was no occlusion. The leveling off was explained as due to the systolic blood pressure being higher than the prevailing intra-muscular pressure at this stage of fatigue. A mathematical equation, the components of which were derived from broad physiological considerations of the factors involved, fitted the observed data accurately.