An Electromyographic Study on Physiological and Psychological Limits of Human Strength.

Abstract

The muscular endurance has been tested on the arm ergometer and the straingauge tensiometer together with recording of the electromyograms from the acting muscles. The test consisted of four different procedures and the results were discussed from view point of physiological and psychological limits of performance. 1. The subject contracted the arm flexor on the ergometer with the load of 1/3 of the maximal strength once a second until an exhaution. It was found that electromyograms of the flexor muscles were gradually increased in voltage and frequency in later stage of work. 2. The subject contracted the arm flexor isometrically against the horizontal bar attached with a straingauge apparatus once two seconds with his maximal effort until an exhaustion. It was found that the electomyograms of the arm flexors were increased remarkably in later stage together with an apparently decreased strength. 3. In later stage of the endurance test on the straingauge tensiometer, the subject was given a sound of "shot" of a starting pistol or a sound of "shout" by himself. It was found that the maximal strength recovered up to the initial level of the stregth and sometimes over the initial level of the strength together with an increase of nervous discharge to the arm flexors. 4. The maximal strength was measured once two seconds after the administration of Amphetamine Sulphate until an almost exhaustion on the same subject. It was worthy to note that the elevated level of the maximal strength after the administration of the drug was almost same as that of "shout". These findings appear to be an additional support of the thesis suggested by Michio Ikai and Arthur H. Steinhaus that in every voluntarily executed, all-out maximal effort, psychologic rather than physiologicl factors determine the limits of performance.