Core Temperature While Swimming in Warm Open Water with and Without a Wetsuit

Triathlon is a popular sport which attract participants from all over the world. In general, triathlon is a safe sport with risk of death being about 1.74 deaths per 100,000 participants (Harris et al., 2017). The swimming portion of the race can be dangerous, posing particular risks due to open water conditions and the physical demands of the event. This study investigated the effects of wetsuit use on core temperature in warm open-water swimming (27.9–28.3°C). Four experienced triathletes (2 males, 2 females; age 49.50 ± 7.83 years) completed two 700-meter open-water swims at a submaximal pace—once wearing their personal full-sleeve wetsuit with a maximum thickness not exceeding 5 mm, and once without a wetsuit. Core temperature was continuously monitored using ingestible temperature pills recording at 15-second intervals. Results revealed significant differences in core temperature responses between conditions. Maximum core temperature was higher in the non-wetsuit (NWS) condition (37.76 ± 0.32°C) compared to the wetsuit (WS) condition (37.29 ± 0.26°C; p = 0.024). Similarly, average core temperature was greater in the NWS condition (37.55 ± 0.29°C) versus WS (37.04 ± 0.30°C; p = 0.019). However, the rate of temperature change was significantly higher in the WS condition (0.00060 ± 0.00036°C/s) than in NWS (0.00027 ± 0.00030°C/s; p = 0.02), indicating more rapid heat accumulation with wetsuit use. These findings suggest that while overall core temperature may be higher in non-wetsuit swimming, wetsuit use accelerates temperature rise, which could pose a greater risk of heat stress in prolonged efforts. Individual variations and non-linear temperature changes highlight the need for more detailed analyses of thermoregulatory responses.