Temperature Regulation during Continuous and Intermittent Exercise in Man

E kblom , B. C. J. G reenleaf , J. E. G reenleaf and L. H ermansen , Temperature regulation during continuous and intermittent exercise in man . Acta physiol. scand. 1971. 81. 1–10. Body temperature changes and heat dissipation responses were studied in three well‐trained men during moderately heavy (60 % of maximal aerobic power) continuous and intermittent exercise at the same average metabolic rate and heat production. The purpose was to determine if hypothetical “work factors” induced specifically by muscular activity influenced body temperature regulation. Compared with continuous work; a) the equilibrium level of rectal temperature (T re ) during intermittent work was elevated 0.35° C which accounted for 21 % of the total T re increase from resting, and b) the decreased sweating of 32 g/(m 2 . hr) during intermittent work resulted in a decreased evaporative heat loss of 18.6 kcal/(m 2 . hr) that could account for the increased intermittent work T re . These responses appear to be manifestations of reduced thermoregulatory efficiency due, perhaps, to non‐linearity in the relationship of body temperature to total work rate or to non‐linearity in the contribution of non‐thermal inputs at work rates above 100 % of max. V̇O 2 . It is also possible that other factors play a part, such as the frequency and duration of the work and rest cycles, rate of limb movement, or circulatory factors related to postural changes.