Hand blood flow at rest and during submaximal exercise in acute and chronic heat stress
Martineaud, J.P.; Raynaud, J.; Duhaze, P.; Vieillefond, H.
Journal de Physiologie 72(2): 233-247
1976
ISSN/ISBN: 0021-7948 PMID: 966181 Document Number: 102108
Three groups of subjects, Europeans without any heat acclimation (called EE), Europeans after 3 wk of acclimatization in India (EI), and Indians in their natural environment (II) were studied during exposure to an ambient temperature of 33.degree. C. Hand blood flow (.ovrhdot.Q), rectal temperature (Tre) and mean cutaneous temperature (.hivin.Tsk) were simultaneously recorded at rest and during 2 periods of muscular exercise (0.4 and 0.7 VO2 max, O2 consumption) of 35 min duration. At rest, .ovrhdot.Q was very high in EE and low in both EI and II. At the onset of exercise, hand vasoconstriction was observed in all cases. During exercise, there was a progressive increase of .ovrhdot.Q until 200% maximum above rest values. At the end of exercise, .ovrhdot.Q was proportional to the intensity of the exercise for each group and inversely proportional to the duration of heat exposure, the highest .ovrhdot.Q was observed in EE, the lowest in II and an intermediate value for EI close to the latter). These differences in hand blood flow could not be explained by differences in deep and/or superficial temperatures between subjects. During chronic heat exposure, there is, especially for an exercising man, a progressive modification of heat transport in the body: i.e., a reduction of skin perfusion and a greater Tre-.hivin.Tsk difference which are both adaptative responses. The value of hand blood flow as an estimation of whole superficial circulation is discussed.