RELATIONSHIP BETWEEN BODY SURFACE COOLING AREA, COOLING CAPACITY, AND THERMOREGULATORY RESPONSES WEARING WATER PURFUSED SUITS DURING EXERCISE IN HUMANS / 体力科学

This study analyzed the effects of various body surface areas being cooled by water-perfused suits (WPS) on thermoregulatory response during exercise in a hot environment. Seven male subjects, dressed in clothing with low moisture permeability (rain coats) over WPS covering the whole body surface except for the face, hands, and feet, performed three sessions of 20-min cycling at low intensity (250w/m²) in a room maintained at 30℃ under six conditions of body surface cooling : whole body (WB), upper body (UB), lower body (LB), lower body except lower legs (LBEL), head and neck (HN), and no body cooling (NBC). The coolant temperature at the inlet was 20℃ for all conditions, and heat extraction (HE) was estimated by the difference between inlet and outlet water temperatures and water flow rate. Esophageal (Tes) and deep thigh temperatures (T-d.thigh) and heart rate (HR) during exercise were significantly (p＜0.01) higher for NBC and HN, and forearm skin blood flow (SkBF) and dehydration (DEH) were significantly (p＜0.01) lower for WB than for other conditions. There was a similar tendency concerning Tes and T-d.thigh among WB, LBEL, and LB ; however, T-d.thigh for UB was significantly (p＜0.01) higher than for WB, LBEL, and LB. In comparison with resting levels, the mean skin temperature (Tsk) and thermal sensation (TS) significantly (p＜0.01) increased for NBC and HN, and decreased for UB and WB, but remained constant for LBEL and LB during exercise. Under all conditions, increases in Tes (ΔTes) and T-d.thigh (ΔT-d.thigh) at the end of exercise were significantly (p＜0.01) increased when less than 40% of the body surface was cooled (Tsk : above 35.8℃, HE : less than 110W). Furthermore, ΔTes at the end of the exercise was related to ΔTsk×SkBF, while the slope of the regression line between those parameters was steeper when ΔTsk×SkBF values were negative, as opposed to positive values. These results suggest that during light exercise under different body surface cooling conditions : 1) UB leads to a high T-d.thigh while Tes, Tsk, and TS are as low as those for WB, 2) critical levels of body surface cooling area causing a decrease in core temperature elevation might exist, and 3) changes in blood circulation due to body cooling might be affecting temperature responses at the end of exercise.

EFFCTS OF VARYING SKIN TEMPERATURE DUE TO SEVERAL TYPES OF CLOTHIG ON TEMPERATURE RESPONSES AND HEAT-STRESS DURING EXERCISE / 体力科学

To clarify the effects of varying skin temperature due to several types of clothing on temperature responses and heat-stress during exercise, we analyzed thermoregulatory responses while wearing various types of sportswear including soccer (SC), baseball (BB), and fencing uniforms (FU), and while wearing water-perfused suits (WS) and vests (WV) during exercise in a hot environment. We also compared these results with those obtained under a semi-nude condition (NU). Eight male subjects performed three 20-min cycling sessions at light intensity (250W/m²) in a room maintained at 28°C (wet-bulb globe temperature, WBGT). The experiment was performed under ten conditions, with six sets of clothing, WS and WV at 14°C (WS14, WV14), 20°C (WS20, WV20) and 26°C (WS26, WV26), and FU, SC, BB or NU. While wearing sport-swear, increases in esophageal (ΔTes), mean skin (Tsk), mean body (Tb) temperature, heart rate (HR), thermal sensation (TS) at the end of exercise, and total sweat loss (<i>m</i>_sw, _tot) during exercise were significantly (p<0.01) higher in BB and FU than in NU. In comparison to WS or WV conditions, ΔTes was significantly (p<0.01) higher under WV conditions than under NU, while there was no significant difference in ΔTes between WS and NU. Tsk, Tb, HR, TS and <i>m</i>_sw, _tot tended to be lower in WS14 and 20, and higher in WV26 than in NU. Under all conditions at the end of exercise, the ΔTes markedly increased when Tsk exceeded 34°C ; and ΔTes was significantly correlated with Tsk (r=0.861, p<0.01) for all conditions except WS14 and 20. For Tsk less than 34°C, however, ΔTes remained constant. ΔTes, Tsk, and Tb significantly correlated with HR (r=0.932, p<0.001), TS (r=0.888, p<0.001), and <i>m</i>_sw, _tot (r=0.961, p<0.001), respectively. These results show that during light exercise under hot conditions, 1) in several types of clothing, a critical level of skin temperature causing core temperature elevation may exist, 2) cooling the skin temperature can alleviate heat-stress due to body temperature elevation, and 3) the semi-nude condition is the simplest method of alleviating core temperature elevation without using body cooling materials such as WS or WV.

EFFECT OF SPORTS WEAR ON THERMOREGULATORY RESPONSE DURING EXERCISE IN A HOT ENVIRONMENT / 体力科学

To clarify the effect of sports wear on exercise-heat stress, we analyzed quantitative differences in thermoregulatory responses among baseball uniforms (BB), soccer uniforms (SC), and swimming trunks (NU) during exercise in a hot environment. Eight male subjects performed three sessions of 20-min cycling at light intensity (250W/m<SUP>2</SUP>) wearing BB, SC and NU in a room maintained at 28°C (wet-bulb globe temperatures, WBGT) . Esophageal (Tes), mean skin (Tsk), and mean body temperatures (Tb), heart rate (HR), thermal sensation (TS), and total sweat loss (<I>m</I><SUB>SW</SUB>) were measured during the exercise. Increases in Tes, Tsk, Tb, HR, and TS during exercise were significantly (p<0, 05) higher, and <I>m</I><SUB>SW</SUB>, was significantly (p<0.001) greater for BB than SC and NU. The increase in Tes at the end of the exercise was 3.0 times higher for BB than NU ; and also 2.0 times higher for SU than NU. Under all conditions, the increase in Tes significantly correlated with Tsk (r=0.634, p<0, 001) and HR (r=0.854, p<0.001) ; <I>m</I><SUB>SW</SUB> also significantly correlated with Tb (r=0.683, p<0.001) at the end of the exercise. These findings suggest that quantitative differences regarding the increase in Tes among BB, SC and NU relate to Tsk elevation due to attenuation of heat dissipation depending on sports wear ; body temperature elevation also relates to the increase in HR and <I>m</I><SUB>SW</SUB> during light exercise in a hot environment.

Effects of Fencing Uniform on Thermoregulatory Responses During Exercise in Hot Environment: Practical Field Study and Laboratory Experiment / 体力科学

The effects of fencing uniforms (U) on thermoregulatory responses were analyzed in both practical field investigation (PFI) and laboratory experiment (LE) . In PFI, six fencers (college-aged) performed regular fencing practice wearing U and wearing a short-sleeved shirt and pants (T) in summer. Rectal temperature (Tr), chest skin temperature (Tch), mask temperature (Tmk), heart rate (HR) and sweat rate (SR) were measured during fencing practice. In LE, seven male college-aged subjects performed three sessions of 20-min cycling at light intensity (250 W/m<SUP>2</SUP>) in a room temperature maintained at 28 WBGT (wet bulb globe temperature) . Esophageal temperature (Tes), mean skin temperature (Tsk), mean body temperature (Tb), HR, and SR were measured during exercise wearing U and in a semi-nude condition (N) . In both PFI and LE, increases in Tch, Tsk, Tb, Tes, Tr and SR were significantly (p<0.001) greater when wearing U than when wearing T and N. In PFI, the maximal value of Tr correlated significantly with the maximal values of Tch (r=0.513, p<0.001) and SR (r=0.635, p<0.001) during practice wearing U and T. In LE, positive correlations between Tsk and Tes (r=0.797, p<0.001), and between Tb and SR (r=0.658, p<0.02) were found at the end of exercise wearing U and N. In PFI, although the Tsk decreased within a few minutes of a decrease in Tmk, a significant relationship between the decrease in Tmk and Tsk or Tr was not observed during fencing practice. These results demonstrate that when wearing U, a higher skin temperature induces core temperature elevation, and higher skin and core temperatures are associated with increases in SR and HR during exercise in a hot environment. Thus, wearing light clothing during exercise, and taking off the fencing jacket and mask during rest periods would be recommended to reduce the heat stress during fencing practice in hot environments.