Effect of mesomorphy on hyperthermia during exercise in a warm, humid environment.

The hyperthermic response to exercise in a warm (30 degrees C), humid (80% relative humidity) environment was obtained for 27 men who exhibited a wide range of body physique in terms of the mesomorphy component of somatotype. Increase in tympanic temperature (Yty) was significantly dependent on mesomorphy rating (X) according to the regression equation Yty = -0.390 + 0.088X. Increase in rectal temperature (Yre) was also significantly dependent on mesomorphy rating according to the equation Yre = -0.100 + 0.066X. The hyperthermic response was significantly correlated with other measures of physique, including ectomorphy, surface area/weight ratio, and body weight, but was not correlated with fatness or fitness. The results support the generalization that during exercise in a warm, humid environment individual differences in heat strain can be highly dependent on physique, especially if fitness and fatness are similar. In this context, mesomorphy appears to provide the optimum description of physique variation. Individuals with a mesomorphy rating greater than 7 warrant designation as being at high risk for heat intolerance during exercise in environments that significantly impair the rate of body heat loss.