To approach the mechanisms in the maturation- and age-related changes of skin blood flow to heat stress and its regional differences, 8 prepubertal boys (8-12 yr), 9 young (20-25 yr) and 9 older (65-77 yr) men were uniformly clamped at 42 ℃ on 5 skin sites (20 cm² of forehead, chest, back, forearm and thigh) for 40 min, respectively. Skin blood flow by laser Doppler flowmetry (LDF), blood pressure and skin and oral (Tor) temperatures were measured during the heating. Tor did not change for the 40-min local heating regardless of group, althouth the boys had significantly higher Tor compared to the other groups. LDF responses reached plateau after increasing for 20-25 min from the beginning of heating, regardless of group and site. Therefore the mean LDF for 35-40 min on each site was defined as maximal LDF. The maximal LDF was then divided by the mean arterial pressure to yield maximal cutaneous vascular conductance (CVCmax). CVCmax was significantly greater in the boys on the forehead (P<0.10), back (P<0.05) and thigh (P<0.05) and lower in the older men on the forearm (P<0.05) and thigh (P<0.10), compared to the young men. However no age-related differences were observed for CVCmax on the chest. These results suggest that modification of cutaneous vasculature as indicated with the maturation- and agerelated differences in CVCmax may be a factor responsible for greater LDF of the boys and lower LDF of the older men (relative to the young men) observed in our previous studies. Furthermore, regional differences may exist in the modification of vasculature in relation to maturation and aging. The estimated maximal oxygen uptake tended to correlate with CVCmax on the forehead in the boys (r=0.69, P=0.06) and on the chest in the older men (r=0.58, P=0.10), suggesting that exercise habits may promote or slow the maturation- or age-related alternations in cutaneous vasculature.

DESCENTE SPORTS SCIENCE Vol.19/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE