Blood temperature and perfusion to exercising and non-exercising human limbs.

Abstract

Temperature-sensitive mechanisms may contribute to blood flow regulation, but the influence of temperature on perfusion to exercising and non-exercising human limbs is not established. Blood temperature (TB ), blood flow and oxygen uptake (VO2 ) in the legs and arms were measured in 16 healthy humans during 90 min of leg and arm exercise and during exhaustive incremental leg or arm exercise. During prolonged exercise, leg blood flow (LBF) was 4-fold higher than arm blood flow (ABF) in association with higher TB and limb VO2 . Leg and arm vascular conductance during exercise compared to rest was related closely to TB (R(2) = 0.91; P < 0.05), plasma adenosine triphosphate (ATP) (R(2) = 0.94; P < 0.05) and limb VO2 (R(2) = 0.99; P < 0.05). During incremental leg exercise, LBF increased in association with elevations in TB and limb VO2 whereas ABF, arm TB and VO2 remained largely unchanged. During incremental arm exercise, both ABF and LBF increased in relation to similar increases in VO2 . In 12 trained males, increases in femoral TB and LBF during incremental leg exercise were mirrored by similar pulmonary artery TB and cardiac output dynamics, suggesting that processes in active limbs dominate central temperature and perfusion responses. The present data reveal a close coupling among perfusion, TB and aerobic metabolism in exercising and non-exercising extremities and a tight association between limb vasodilatation and increases in plasma ATP. These findings suggest that temperature and VO2 contribute to the regulation of limb perfusion through control of intravascular ATP.