Relationship between thermoregulation and cold-induced vasodilation during cold exposure with regard to maximal oxygen intake / 体力科学

ABSTRACT

Based on the maximal oxygen intake (VO<SUB>2</SUB>max), 24 male students were classified into high (H-G), middle (M-G) and low (L-G) groups of the VO<SUB>2</SUB>max level. In each VO<SUB>2</SUB>max level group, thermoregulation characteristic values during cold exposure at an ambient temperature (Ta) of 12°C were compared with several parameters of cold-induced vasodilation (CIVD) measured at 28°C (observation 1) and the parameters measured after 30 min from the start of 60-min cold exposure (observation 2) . The relationship between CIVD as a peripheral vasomotor regulation response, and autonomic thermoregulatory response was examined. The results are as follows<BR>A . H-G showed the smallest decreases in the rectal temperature (Tre) and in mean skin temperature (Tsk), and these parameters decreased as VO<SUB>2</SUB>max decreased. Enhancement of metabolic heat production (M) was highest in H-G and lowest in L-G.<BR>B . In the observations 1 and 2 of the CIVD tests, mean skin temperature (MST), temperature at first rise (TFR) and resistance index (RI) increased with rise in VO<SUB>2</SUB>max, while time of temperature rise (TTR) decreased. In the observation 2, TFR remained low by decreased temperature before water immersion (TBI) and, with TBI taken into consideration, no significant change in RI was observed except only in L-G.<BR>C. MST, TTR and RI in the CIVD measurements (observation 1 and 2) were significantly correlated with the mean thermoregulation characteristic value during 30-60 min after the start of cold exposure (the second half period) .<BR>D. During the second half period of cold exposure, significant negative correlations were observed between Tsk and body fat% (BF%) and between M and BF %. VO<SUB>2</SUB>max was significantly correlated with RI, Tre, Tsk and M.<BR>These results indicate that difference in physical fitness for endurance is clearly reflected in the values of cold-induced vasodilation in thermoneutral zone and during cold exposure. The peripheral vascular resistance of finger increased during cold exposure from that in thermoneutral zone causing decrease of finger skin temperature. After that, due to hunting reaction, the peripheral vascular resistance decreased, and a correspondance was observed between effectiveness in raising finger skin temperature through increase in skin blood flow and physical fitness for endurance. An interrelation was observed between the local cold resistance of peripheral vasomoter during exposure of finger to ice water and the whole cold resistance of autonomic temperature regulation during cold exposure of the whole body. It may be inferred that the subjects with high physical fitness for endurance have low insulative of body fat but have good cold tolerance by enhancement of heat production and preservation of skin temperature.