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

Abstract

New Findings What is the central question of this study?Temperature-sensitive mechanisms are thought to contribute to blood-flow regulation, butthe relationship between exercising and non-exercising limb perfusion and blood temperatureis not established. What is the main finding and its importance?The close coupling among perfusion, blood temperature and aerobic metabolism in exercisingand non-exercising extremities across different exercise modalities and activity levels and thetight association between limb vasodilatation and increases in plasma ATP suggest that bothtemperature- and metabolism-sensitive mechanisms are important for the control of humanlimb perfusion, possibly by activating ATP release from the erythrocytes.Temperature-sensitive mechanisms may contribute to blood-flow regulation, but the influenceof temperature on perfusion to exercising and non-exercising human limbs is not established.Blood temperature (TB),bloodflowandoxygenuptake( ̇VO2)inthelegsandarmsweremeasuredin 16 healthy humans during 90 min of leg and arm exercise and during exhaustive incrementalleg or arm exercise. During prolonged exercise, leg blood flow (LBF) was fourfold higher thanarm blood flow (ABF) in association with higherTBand limb ̇VO2.Leg and arm vascularconductance during exercise compared with rest was related closely toTB(r2=0.91;P<0.05),plasma ATP (r2=0.94;P<0.05) and limb ̇VO2(r2=0.99;P<0.05). During incrementalleg exercise, LBF increased in association with elevations inTBand limb ̇VO2,whereas ABF,armTBand ̇VO2remained largely unchanged. During incremental arm exercise, both ABFand LBF increased in relationship to similar increases in ̇VO2.In 12 trained males, increasesin femoralTBand LBF during incremental leg exercise were mirrored by similar pulmonaryarteryTBand cardiac output dynamics, suggesting that processes in active limbs dominatecentral temperature and perfusion responses. The present data reveal a close coupling amongperfusion,TBand aerobic metabolism in exercising and non-exercising extremities and a tight