As global temperatures continue to rise, the threat of heat stroke is becoming a critical concern, especially for athletes involved in high-intensity sports like tennis. Players often find themselves competing in grueling matches that can extend up to five hours under intense sunlight. The Tokyo Olympic Games in 2021 brought this issue to the forefront, prompting players to call for effective measures to combat heat-related risks. In response, the International Tennis Federation (ITF) implemented the “Extreme Weather Policy,” aimed at managing match conditions based on temperature. Despite these efforts, heat-related illnesses remain a significant challenge in the sport.
Tennis is played on various surfaces, including hard courts, sand-filled artificial grass, and clay, each presenting unique microclimatic conditions that differ from standard weather measurements. The wet-bulb globe temperature (WBGT) serves as a vital index for assessing thermal environments and is closely associated with the risk of heat stroke. While several studies have explored WBGT variations across different tennis court surfaces, many have limitations, such as only measuring during specific times of the day or failing to compare results with nearby weather stations.
To address these limitations, a research team from Japan, led by PhD student Hiroki Yamaguchi from Doshisha University and Professor Kojiro Ishi, conducted a comprehensive study on the heat environment of various tennis courts using WBGT meters. Their findings, published in the journal Scientific Reports in July 2024, were motivated by Yamaguchi’s personal experiences with heat stroke during matches. He stressed the importance of understanding the heat conditions on different court surfaces to develop effective exercise guidelines and improve heat management in sports.
The research team installed WBGT meters on an outdoor hard court, a sand-filled artificial grass court, and a clay court, taking hourly measurements from 9 AM to 5 PM on weekdays between June and September 2022. They compared these on-site measurements with data from the nearest Japan Meteorological Agency station (JMA WBGT), following the Japan Tennis Association’s heat stroke prevention guidelines.
The results revealed significant differences between the JMA WBGT and the on-site WBGT values. Hard courts showed higher median on-site WBGT values at the “Warning” level (25°C to 28°C), while sand-filled artificial grass courts reached the “Severe Warning” level (28°C to 31°C), and clay courts exceeded the “Danger” level (above 31°C) compared to JMA WBGT. These findings highlight the critical need for on-site WBGT measurements and proactive heat management strategies, such as reducing afternoon matches and considering scheduling games in the early morning, evening, or nighttime.
Yamaguchi emphasized the study’s importance, stating, “The results underscore the necessity of on-site WBGT measurements and the need to consider court surface and match timing to protect players, coaches, referees, and spectators from heat stroke.” He also recommended that future guidelines incorporate body heat balance models, such as Predicted Heat Strain (PHS), to enhance heat safety strategies.
Hiroki Yamaguchi, a dedicated PhD student at Doshisha University, brings a wealth of experience in tennis as a player, coach, and tournament organizer. His research interests span sports science, exercise physiology, heat exhaustion, and environmental physiology, all driven by his firsthand experiences with the varying heat conditions on tennis surfaces.