Regional skin temperature responses to exhaustive cycling under normoxia and normobaric hypoxia in trained and non-trained men

The combined effects of exercise bout, body region and hypoxic severity on post-exercise skin temperature (Tₛₖ), measured by infrared thermography (IRT), remain unclear. Twenty-four healthy men (12 trained cyclists, 12 non-trained controls) completed three sessions under normoxia (FiO₂ 0.209) and normobaric hypoxia simulating ≈ 2000 m (0.16) and ≈ 3000 m (0.14), each comprising graded and constant-load cycling bouts to exhaustion. Anterior trunk and thigh Tₛₖ were imaged at rest and immediately after each bout and analysed by mixed-design ANOVA (Time, Region, FiO₂ within-subject; Group between-subject). Tₛₖ fell over time, more and earlier at the trunk than at the thigh (− 4.4 vs. − 0.9 °C), reversing the pre-exercise trunk–thigh gradient. Mean Tₛₖ did not differ between oxygen conditions, but lower FiO₂ amplified and advanced the decrease at both regions (Time × FiO₂); the Time × Region × FiO₂ interaction was not significant. Trained men were warmer at rest at both regions; exercise abolished this difference at the trunk but widened it at the thigh. Exploratory correlations linked Tₛₖ inversely to body fat and positively to VO₂max. Post-exercise Tₛₖ therefore tracks region- and time-specific thermoeffector activity, not whole-body heat content; because skin blood flow and core temperature were not measured, this interpretation remains inferential.