[Muscle activity and heart rate during rhythmical work using a hand ergometer. II. Heart rate, mechanical and bioelectrical activity of muscles during work with different loads and in relation to endurance].

The study has been made to analyse changes in heart rate, in mechanical and bioelectrical muscle activity during thythmical handgrip contractions. Loads of 20% to 100% of the maximal voluntary contraction (MVC) were applied. The working frequency was 30 cpm. With loads of 40%--100% of the maximal voluntary contraction (MVC) the following characteristic changes were obtained: Both the plane of the mechanogram and the duration of the mechanogram increased permanently. The heart rate rose to the end of the experiment and so did the EMGs of the flexor, the extensor, the brachioradial muscle and the muscle of the thenar. The rate of the rise (%/s) of all physiological functions was greatest during maximal load test and decreased with decreasing contraction strength. The endurance as a function of the force showed a parabolic curve. The physical endurance capacity of this rhythmical hand work is between 20% and 40% MVC.