Julien D Périard, Sébastien Racinais, Wade L Knez, Christopher P Herrera, Ryan J Christian, Olivier Girard
Athlete Health and Performance Research Centre, ASPETAR, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar
Objectives: This study compared the thermal, physiological and perceptual responses associated with match-play tennis in HOT (∼34°C wet-bulb-globe temperature (WBGT)) and COOL (∼19°C WBGT) conditions, along with the accompanying alterations in match characteristics.
Methods: 12 male tennis players undertook two matches for an effective playing time (ie, ball in play) of 20 min, corresponding to ∼119 and ∼102 min of play in HOT and COOL conditions, respectively. Rectal and skin temperatures, heart rate, subjective ratings of thermal comfort, thermal sensation and perceived exertion were recorded, along with match characteristics.
Results: End-match rectal temperature increased to a greater extent in the HOT (∼39.4°C) compared with the COOL (∼38.7°C) condition (p<0.05). Thigh skin temperature was higher throughout the HOT match (p<0.001). Heart rate, thermal comfort, thermal sensation and perceived exertion were also higher during the HOT match (p<0.001). Total playing time was longer in the HOT compared with the COOL match (p<0.05). Point duration (∼7.1 s) was similar between conditions, while the time between points was ∼10 s longer in the HOT relative to the COOL match (p<0.05). This led to a ∼3.4% lower effective playing percentage in the heat (p<0.05). Although several thermal, physiological and perceptual variables were individually correlated to the adjustments in time between points and effective playing percentage, thermal sensation was the only predictor variable associated with both adjustments (p<0.005).
Conclusions: These adjustments in match-play tennis characteristics under severe heat stress appear to represent a behavioral strategy adopted to minimiZe or offset the sensation of environmental conditions being rated as difficult.
The development of hyperthermia during exercise in the heat, a state in which body core temperature (Tc) exceeds 38.5°C, is directly related to relative exercise intensity and the prevailing environmental conditions. Such increases in Tc under heat stress have been shown to impair prolonged continuous and intermittent exercise performance. The rise in thermal strain in hot conditions is also associated with elevated physiological and perceptual strain compared with exercise performed in cooler conditions, and can lead to heat-related illnesses (eg, heat exhaustion and heat stroke). Owing to the nature of the game, tennis is characterized as high-intensity intermittent exercise; however, its overall metabolic response is similar to prolonged moderate-intensity exercise (eg, running and cycling). This stems from work periods performed at 60–75% of maximal oxygen consumption (VO2max), interspersed with periods of light activity or rest (ie, work-to-rest ratios of 1:2 t 1:5). Consequently, the mean relative exercise intensity for a match is ∼55% VO2max and duration is from 1 to 6 h. The overall energetic demands of match-play tennis and the rate of rise in Tc are therefore strongly influenced by point duration, as longer rallies result in greater metabolic loads.