Environmental and Psychophysical Heat Stress in Adolescent Tennis Athletes

Purpose: We investigated the environmental conditions in which all outdoor International Tennis Federation (ITF) junior tournaments (athlete ages: <18 y) were held during 2010-2019. Thereafter, we performed a crossover trial (ClinicalTrials.gov: NCT04197375) assessing the efficacy of head-neck precooling for mitigating the heat-induced psychophysical and performance impacts on junior athletes during tennis match play. Methods: ITF junior tournament information was collected. We identified meteorological data from nearby (13.6 [20.3] km) weather stations for 3056 (76%) tournaments. Results: Overall, 30.1% of tournaments were held in hot (25 degrees C-30 degrees C wet-bulb globe temperature [WBGT]; 25.9%), very hot (30 degrees C-35 degrees C WBGT; 4.1%), or extremely hot (>35 degrees C WBGT; 0.1%) conditions. Thereafter, 8 acclimatized male junior tennis athletes (age = 16.0 [0.9] y; height = 1.82 [0.04] m; weight = 71.3 [11.1] kg) were evaluated during 2 matches: one with head-neck precooling (27.7 degrees C [2.2 degrees C] WBGT) and one without (27.9 degrees C [1.8 degrees C] WBGT). Head-neck precooling reduced athletes' core temperature from 36.9 degrees C (0.2 degrees C) to 36.4 degrees C (0.2 degrees C) (P =.001; d = 2.4), an effect reduced by warm-up. Head-neck precooling reduced skin temperature (by 0.3 degrees C [1.3 degrees C]) for the majority of the match and led to improved (P <.05) perceived exertion (by 13%), thermal comfort (by 14%), and thermal sensation (by 15%). Muscle temperature, heart rate, body weight, and urine specific gravity remained unaffected (P >=.05; d < 0.2). Small ormoderate improvements were observed in most performance parameters assessed (d = 0.20-0.79). Conclusions: Thirty percent of the last decade's ITF junior tournaments were held in hot, very hot, or extremely hot conditions (25 degrees C-36 degrees C WBGT). In such conditions, head-neck precooling may somewhat lessen the physiological and perceptual heat strain and lead to small to moderate improvements in the match-play performance of adolescent athletes.