夏季, 運動時における長距離選手の耐暑性におよぼす2〜3の因子

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The present study was undertaken in order to investigate some factors limiting work performance in summer-meteorological conditions. Six distance runners performed on a bicycle ergometer at a constant work load which was set a 65-70% max VO_2 measured at a comfortable temperature. The subject performed a full time 60-min work load with an identical work load both in cool (23.5℃) and hot (33.5℃) environments at 60% relative humidity. Three subects were able to perform the standard test in the hot environment, whereas the remainders failed to complete it. The former was referred to as group 1 and the latter as group 2. The followings are some findings : 1. In the hot environment, VO_2 cost for the work was raised to 75% (mean value) from 64% measured in the cool environment. The increase in submaximal VO_2 might have been due to the additional O_2 requirements for peripheral circulation, sweating. A decrease in the efficiency of oxidative phosphorylation in the working muscle cells may have been due to hyperthermia because of the increased O_2 cost. 2. When the work was terminated at higher levels of ambient temperature, the physiological responses were somewhat different among the three men of group 2. One subject showed a typical symptom of hyperthermia indicating Tr 39.9℃, and HR 183 bpm. The hyperthermia of the subject was associated with lower sweat rate. The second man terminated the work with Tr 39.5℃. In addition, the subject exhibited pul monary hyperventilation when he was forced to terminate the work. The third subject of group 2 stopped the work with the highest HR of 191 before the internal temperature approached a critical poaint. However, based on the observation that his blood lactate was elevated and that the subject was almost exhausted, his work load, which was about 60% in the cool environment, might have become highly intense at the hot environment. 3. The circulatory burden due to heat dissipation was obviously greater for those of group 2 than for those of group 1. Such a phenomenon reflected in the greater HR was associated with a rapid rise in Tr during the work. 4. A higher rate of body heat storage was exhibited by the subjects of group 2. This might have played a significant role in decreasing the work and producing hyperthermia. 5. With one exception hyperthemia, which was a main factor in limiting work performance was associated with lower sweat volume. In addition, sweating sensitivity reflected in the steeper slope of sweat rate-core temperature relation was greater for group 1 than for group 2, although there was no difference in sweating onset between two This groups. sweat rate-core temperature relation may have served an important role in prolonging work in the hot environment. 6. The sweat rate of one subject in group 2 was 47% greater than the mean value of group 1. Loss of water and electrolytes due to excessive dehydration might have resulted in disturbing his internal homeostasis. This indicates that effective amounts of sweating are very important to perform strenuous exercises in heat.
中京大学の論文
1976-09-01

夏季, 運動時における長距離選手の耐暑性におよぼす2〜3の因子

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