Dynamics and topography of human temperature regulation in response to thermal and work load

Summary

Climatic chamber experiments were carried out with male subjects who were submitted to various rapid temperature changes. All experiments were performed first with the subjects at rest and later at work on a bicycle ergometer. The aims of the study were 1) to obtain quantitative data enabling to determine effects of a) abrupt thermal load, b) abrupt work load, and c) combined load on the topography and the dynamics of temperatures and effectors, and 2) to answer the question whether the effects of combined load may be computed by a linear superposition of pure thermal plus pure work load.

Skin temperatures generally respond more directly to abrupt changes of thermal than of work load. This is in contrast to the dynamic behaviour of central temperatures which moreover exhibit the interesting effect of a transient paradoxical respone both to the onset of work and of thermal load.

Time constants of the dynamics of metabolic heat production are high in response to changes of thermal load as compared to the time constants at the onset and end of worl. Generally the time constants of skin temperatures are shorter at rest than at work. Temperature topography changes only to a small extent in exercising subjects.

The central temperature increase to combined thermal and work load is not significantly different from the added amount of temperature increases due to pure thermal and to pure work load. This suggests a quasi-linear superposition of both thermal effects and confirms, in accordance with further evidence of this and former studies, the hypothesis that work load does not interfere non-linearly with the regulatory processes. However, an input from thermosensitive elements in the muscles should be assumed.