Impact of summer heat on male children's physiological responses during football training

Background: As summer temperatures rise due to climate change, the Pediatrics Society calls for more research on children's core body temperature. This study aims to analyze these concerns by investigating the specific effects of heat exposure on children's physiological parameters such as body temperature during football training. Methods: This case-crossover study investigated the effects of heat on several physiological parameters (e.g., ear and skin temperature) by monitoring 51 male children (aged 8–12 years) during outdoor football training sessions. Participants wore wearable sensors and were either part of a club football team (club: n = 30) or part of a football camp (camp: n = 21). Both groups were monitored twice. Club participants were monitored during two separate training days, one session in warm weather (≥25 °C) and one session in moderate weather (<20 °C). Camp participants were monitored during two training sessions on the same warm summer day (≥25 °C). For both groups, urine density was measured before and after each training session to assess hydration status. A mixed linear regression was performed separately for the two settings. Results: Ear and skin temperatures were significantly higher for both club and camp participants during the warm observation period compared to moderate outdoor temperatures. During training periods, outdoor temperature regularly exceeded 32.3 °C, a level at which the American College of Sports Medicine advises cessation of training. In this study, outdoor temperature had no impact on hydration status. The mixed linear regression models showed that outdoor temperature significantly influenced core and skin temperatures. Conclusion: Our results showed a significant but safe increase in physiological parameters, like ear and skin temperatures, during summer football training, with no severe heat strain symptoms observed, highlighting the need for further research on long-term effects.