A new preventive measures against exertional heat illness based on thermoregulatory responses in intense radiant heat environments

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K17622
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 59030:Physical education, and physical and health education-related
• Research Institution: Kyoto Institute of Technology
• Principal Investigator: Yamashita Naoyuki 京都工芸繊維大学, 基盤科学系, 准教授 (70800738)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 熱中症予防 / 日射 / 体温調節 / 歩行 / 走運動 / 脱水

Outline of Final Research Achievements

This study investigated the effects of the presence or absence of simulated solar radiation (both, wet-bulb globe temperature, WBGT, was set at approximately 28°C) on metabolic, cardiovascular, and thermoregulatory responses at rest and during low- and moderate-intensity exercise. The results showed that the increase in rectal temperature at rest and during low-intensity exercise was not significantly different in the presence or absence of simulated solar radiation. However, it became greater at higher exercise intensities. These responses in core temperature elevation appear to be partially compensated by increased thermoregulatory responses, i.e., increased sweat rate responses. However, the subjects subjectively felt hotter and more uncomfortable in the presence of solar radiation. These results suggested that abundant fluid restoration is required during rest and exercise in the presence of solar heat loads.

Free Research Field

運動生理学・環境生理学

Academic Significance and Societal Importance of the Research Achievements

本研究は、日射が体温調節反応に及ぼす影響を明らかにし、運動時の体温管理に重要な知見を提供するものである。具体的には、日射がある場合（日向、湿球黒球温度28℃）と日射はないが湿球黒球温度が同程度の条件（約28℃）、および日陰（湿球黒球温度25℃）での安静時や低強度運動時においては、直腸温の上昇度には大きな差がないことが示唆された。しかし、日射のある場合には暑さや不快感が増し、発汗量が多くなるため、積極的な水分補給が必要である。一方、運動強度が最大酸素摂取量の60%になると、日射がある場合には運動の終盤に直腸温が有意に高くなるため、特に1時間以上の運動時には後半から終盤にかけて注意が必要である。