doi:10.1007/s40279-025-02193-7engJames, CarlMúñiz-Pardos, BorjaIhsan, MohammedLo, Ka-KayLam, Wing-KaiIglesias, Dani PeñaAngeloudis, KonstantinosTeng, YiJiao, JiaoHu, KeWong, KaKiGuppy, FergusRacinais, SébastienChalmers, SamuelMigliorini, SergioWu, KennethPitsiladis, YannisThermal and biomechanical responses of amateur, elite and world cup athletes during a world cup sprint triathlon in the heatART-2025-143763Objectives: Core temperature (TCORE), skin temperature (TTORSO) and running kinematics were measured across different athlete categories at a World Cup Sprint Triathlon, occurring during a heatwave (~ 25–31 °C Wet Bulb Globe Temperature [WBGT]). Methods: Sixty-six triathletes participated: 21 World Cup (7 females), 32 Hong Kong-Elite (HK-Elite; 8 females) and 13 Amateur (6 females). Results: Seventeen triathletes displayed a TCORE > 40.0 °C and two > 41.0 °C. Peak TCORE was not different between athlete categories (World Cup: 39.7 ± 0.6 °C; HK-Elite: 39.9 ± 0.8 °C; Amateur: 39.5 ± 0.8 °C; p = 0.357). However, there was an interaction between race phase and category (p = 0.001). Changes in TCORE for World Cup (2.4 ± 0.4 °C) and HK-Elite (2.5 ± 1.0 °C) were greater than for Amateurs (1.5 ± 0.7 °C). Peak TTORSO was higher in HK-Elites during afternoon races compared with morning World Cup races (p < 0.001). TTORSO reduced during the swim (pbonf < 0.001), then increased during the bike (pbonf < 0.001) but not run (pbonf = 1.00). World Cup athletes (3.15 ± 0.23 m) displayed longer strides (HK-Elites: 2.64 ± 0.35 m; Amateurs: 2.18 ± 0.30 m; pbonf < 0.001), shorter contact times (209.3 ± 13.7 ms; HK-Elites: 237.8 ± 23.0 ms; Amateurs: 262.9 ± 31.0 ms, pbonf < 0.001) and higher stride frequency (182.9 ± 6.3 strides.min−1) than HK-Elites (173.9 ± 6.8 strides.min−1) and Amateurs (173.2 ± 8.7 strides.min−1, pbonf < 0.001), which were comparable. There were no biomechanical changes over time and no interactions. Conclusion: Different athlete categories displayed comparable peak TCORE responses. Amateur triathletes tolerated TCORE > 40.0 °C without heat illness symptoms. TCORE may rise > 41 °C during a sprint triathlon held under Blue flag conditions (~ 26 °C WBGT), questioning the suitability of sprint-distance triathlons as a safer alternative to Olympic-distance triathlons under Red/Black flag conditions (> 30.1 °C WBGT).2025http://zaguan.unizar.es/record/15369210.1007/s40279-025-02193-7http://zaguan.unizar.es/record/153692oai:zaguan.unizar.es:153692SPORTS MEDICINE (2025), [12 pp.]byhttps://creativecommons.org/licenses/by/4.0/deed.esinfo:eu-repo/semantics/openAccess