Effects of repeated fatiguing rhythmical hand work.

In a model work place (hand-grip dynamometer), eleven subjects performed rhythmical hand-grip contractions to exhaustion (frequency 30/min). In each working cycle the contraction and rest phases were distinguished. The work to exhaustion was repeated four times (four working periods with 156-min rest intervals). The tests were performed at 40, 60, 80, 100% MVC. Analysis of Variance showed no difference in the group means (mean values of each working period and load level) for the duration of the contraction or rest phases, the integrated bioelectrical muscle activity (iEMG) of flexors, extensors, brachioradialis (iEMG referred to working cycle and contraction phase) or iEMG of the thenar muscles (referring to the working cycle), or in the duration of the R-R interval in the ECG during comparable periods of the experiments. The endurance times decreased from working period 1-4, and a similar decrease occurred in the force-time product. It may be concluded from these results that 15 min rest is insufficient for adequate recovery from hand-exhaustion exercise.