Arm and leg intravascular temperatures of men during submaximal exercise

Rectal (Tre) and blood temperatures in the femoral artery (Tfa), femoral vein (Tfv), axillary artery (Taa), and axillary vein (Tav) were determined in three men over a range of steady-state treadmill exercise (173-401 W/m2) in a 24 degree C db, 15 degree C wb environment. When the men were standing quietly before the walks Tre greater than Tfa greater than Taa greater than Tfv greater than Tav, indicating that under these resting conditions both the arms and the legs served as avenues for arterial heat dissipation. By the end of all 1-h walks, Tre, Tfa, Tasa, and Tfv had increased in a linear fashion with work load, Tav had dropped, and Tre greater than Tfv greater than or equal to Tfa greater than or equal to Taa greater than Tav. The maintenance or expansion of axillary arteriovenous temperature differences during exercise indicated that the less active arms continued to serve as routes for arterial heat loss. The lack of femoral arteriovenous temperature differences demonstrated that under these steady-state exercise conditions there was little or no net vascular heat transfer between the active legs and the central circulation. Rectal-femoral intravascular temperature differences at rest and over the full range of submaximal work employed favor heat transfer from the rectum to the circulation. Consequently the rise in Tre during leg work was considered the result of a reduction in local heat dissipation and some possible heat gained from nearby intrapelvic muscles.