The variation of hand steadiness with physical stress

The performance of 12 subjects in a hand steadiness task was compared at different work loads. Hand steadiness expressed in the form of values of hand shakiness was found not to increase linearly with work intensity. On the contrary, the relation between hand shakiness and activation level, induced by physical work, was found to be positively accelerated by an exponent of 1.6. Subjective effort measured by a ratio estimation method grew, likewise, according to a positively accelerating function with an exponent of about 1.6, while subjective effort according to the "RPE" category scale like hear rate grew linearly with work load.