Reductions in cardiac output, central blood volume, and stroke volume with thermal stress in normal men during exercise.

Abstract

Observations on heat-acclimatized men by As- mussen (1) and Williams and colleagues (2) showed no increase in cardiac output above the normal response during exercise in a hot, humid environment. Indeed, Asmussen found decre- ments in cardiac output below normal responses if moderate work in the heat (32C, 80% rela- tive humidity) was prolonged from 30 to 60 minutes. No systematic study has been reported of cardiac output during exercise at high ambient temperature in men unacclimatized to heat.