Thermoregulation during static work with the legs.

Sustained static work with the legs, i.e., holding a weight of about 10% of maximal isometric strength for 25 min was compared to dynamic exercise on a bicycle ergometer causing the same rate of heat production. In the static work the subjective feeling of exertion was very high and the effort maximal. The pronounced increase in heart rate and blood pressure and a typical flush of the face and chest (flush areas) indicated a high sympathetic tonus. Plasma catecholamine levels were 1.3 times higher (significant at the Pless than or equal to 0.05 level) after static work than after dynamic work. Although the sustained static work was nearly maximal, the rate of increase in sweating and the change in core temperature during work were not different from the responses to dynamic work.