Core temperature responses in world-class triathletes during the Tokyo 2020 Olympics and 2019 to 2021 World Triathlon Championship Series

Abstract

Purpose: To characterise core temperature (Tcore) responses, its increase (∆Tcore) and rate of increase (∆Tcore/∆t) in elite triathletes. Methods: A total of 50 Tcore recordings were obtained from 14 national team triathletes—including Olympic medallists—(7 males: 177 ± 5 cm, 68.1 ± 5.7 kg; 7 females: 164 ± 9 cm, 56.6 ± 5.1 kg) using a telemetric capsule during eight international triathlons (Summer Olympics and World Triathlon Championship Series). Events included mixed team relay (≈20 min), sprint (≈50 min), and standard (≈110 min) formats in temperate and hot environments (distinguished by a heat index threshold of 27 °C). Results: Tcore increased from start (37.6 ± 0.6 °C) to post-swim (38.3 ± 0.7 °C, p < 0.001), then to post-bike (39.3 ± 0.7 °C, p < 0.001), and finally to post-run (39.8 ± 0.8 °C, p < 0.001). ∆Tcore/∆t was the highest during the swim (p ≤ 0.001), ∆Tcore during bike (p ≤ 0.007), and Tcore during run (peak value 41.3 °C) sections. In all, 20 datasets reached ≥ 40 °C and 12 ≥ 40.5 °C. Tcore (but not ∆Tcore/∆t) as well as durations spent ≥ 38.5 °C and ≥ 40 °C were higher in hot than temperate (p ≤ 0.023) environments. Tcore was higher in males than females (p = 0.031), but there was no difference in duration ≥ 38.5 °C or ≥ 40 °C. Conclusion: Current data confirmed that triathletes reach high Tcore toward the end of a triathlon but showed that swim and bike sections are responsible for the highest rate and magnitude of increase, respectively. While Tcore did not increase more when competing in the heat, the time spent ≥ 38.5 °C and ≥ 40 °C was higher.