Resort operators often do not allow children to use hot tubs/whirlpools because of the general belief that children cannot tolerate even a short exposure to warm water (40℃). This belief is based on body size characteristics and under developed thermoregulatory responses of children. Therefore, we measured anthropometric, thermoregulatory, and immersion time required to increase core temperature at 38.5℃, on 14 female subjects (7-23 years). All subjects tolerated 10 minutes of immersion safely, but indicated they would have voluntarily exited the water earlier. Warming rates were somewhat related to body type, but did not depend on age. Healthy female children (>7 years) could therefore safely tolerate 5 to 10 minutes of warm water immersion with adult supervision.
Doupe, Malcolm B.; Kenny, Glen P.; White, Matthew D.; and Giesbrecht, Gordon D.
"Thermoregulation and Rate of Body Warming During Warm Water (40℃) Immersion in Female Children and Adults,"
Visions in Leisure and Business: Vol. 15:
2, Article 7.
Available at: https://scholarworks.bgsu.edu/visions/vol15/iss2/7