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Endurance Training/Cardiorespiratory

(07) PERCEPTUAL ADAPTATIONS INDUCED BY HEAT ACCLIMATION/ACCLIMATIZATION IN ENDURANCE ATHLETES: A SYSTEMATIC REVIEW AND META-ANALYSIS

Friday, July 14, 2023
10:00 AM – 10:15 AM East Coast USA Time
Location: Milano I-II
Abstract Details: INTRODUCTION: Around the world, increasing occurrences of extreme heat at major sporting events has challenged athletes and supporting staff into establishing various training protocols to mitigate the dangers of exercising in extreme heat conditions. Previous literature has acclaimed that exercise in hot and humid environments contribute to surges in physiological and thermal strain, risk of heat illness, decreases in cognitive function, and deterioration of physical performance. Heat acclimation/heat acclimatization (HA) are implemented to alleviate these issues, as chronic environmental heat stress exposure elicits thermoregulatory, physiological, and perceptual adaptations critical for optimizing athlete performance in the heat. PURPOSE: The purpose of this study was to assess and review perceptual HA-induced adaptations, more specifically thermal sensation and rate of perceived exertion (RPE), from studies incorporating endurance-trained athletes alone. METHODS: A collection of data gathered from 23 studies published on PubMed, Scopus, SPORTDiscus, and Cochrane-Library, was used for analysis and review. Furthermore, observed perceptual adaptations were differentiated between short-term HA (< 7 days; STHA) and medium-term HA (8-13 days; MTHA) interventions. RESULTS: HA produced a significant, moderate reduction in mean thermal sensation during exercise in the heat (Hedges’ g [95% confidence intervals] = 0.69 [0.44-0.93], p < 0.05). MTHA produced a greater percentage decrease in mean thermal sensation compared to STHA (8.9 ± 6.3 and 7.0 ± 4.6%, respectively). Additionally, mean thermal sensation is most impacted under controlled intensity protocols (0.84 [-0.13-1.82]) compared to controlled hyperthermia, passive heating, and self-regulated acclimation protocols (0.71 [0.42-1.00], 0.73 [-0.36-1.83], 0.51 [-0.09-1.12], respectively). HA reduced mean RPE during exercise in the heat by a significant, moderate effect (0.45 [0.17–0.73], p < 0.05). MTHA elicited a moderate reduction in mean RPE (13.3%). In comparison, STHA showed a small reduction in mean RPE (8.3%). Mean RPE is most impacted under passive heating protocols (0.78 [0.10-1.47]) compared to controlled hyperthermia, controlled intensity, and self-regulated acclimation protocols (0.34 [-0.02-0.70], 0.59 [-0.36-1.54], 0.45 [-0.33-1.23], respectively. CONCLUSIONS: Longer duration HA protocols decreased mean thermal sensation greater than shorter duration HA protocols. For mean thermal sensation, controlled intensity protocols are most impactful compared to controlled hyperthermia, passive heating, and self-regulated acclimation conditions. HA protocols displayed a moderate reduction in RPE during exercise, with longer duration protocols providing the most prominent reductions. For mean perceived exertion, passive heating conditions are most impactful compared to controlled hyperthermia, controlled intensity, and self-regulated acclimation conditions. PRACTICAL APPLICATIONS: This meta-analysis expands current data surrounding the influence of HA on thermal sensation and RPE during exercise in the heat, allowing for more specialized selection of HA protocols for endurance athletes. Reduced thermal sensation and RPE for exercise in the heat may allow selection of higher exercise intensities, which likely contributes to increased power output and enhanced performance in the heat. 

Acknowledgements: None