Impact of Various 10-min Cooling Breaks on Internal Body Temperature Responses During Subsequent Intermittent Exercise in the Heat: Application to Tennis

Assess the effectiveness of three cooling strategies during a 10-min break vs. no break or no cooling on internal body temperature responses during an intermittent treadmill exercise simulating the intensity of a tennis match. Twelve physically active females (mean ± SD; age, 26 ± 3 years; height, 167.0 ± 4.8 cm; body mass, 58.2 ± 4.2 kg; VO2peak 46.2 ± 2.5 mL/kg/min) completed five 90-min intermittent exercise trials in the heat (WBGT 30.9 ± 0.2 °C) with a 10-min break in different cooling groups: cold water immersion (CWI), ice towel with dampened towels (Towel), cooling vest (Vest), passive rest (Passive), and no break (None). Rectal temperature (Trec), skin temperature (Tsk), and heart rate (HR) were monitored throughout the trials. There was a significant difference in ΔTrec between None and CWI (P < 0.001, d = 1.71). The effect size for ΔTrec indicated a moderate impact with a 10-min break using Towel, Vest and Passive, without a significant difference from None (P > 0.05, d = 0.52–0.67). CWI had a significantly greater ΔTrec during the first 15-min of subsequent exercise period compared to Vest and Passive while there was no significant difference during a 10-min break between the cooling groups. The effects of cooling on Tsk and HR were not maintained at the end of exercise period. A 10-min break with CWI effectively attenuated the rise in internal body temperature following intermittent treadmill exercise. A 10-min CWI break may be a potential strategy to mitigate the risk of exertional heat illnesses during tennis tournaments in hot conditions, however the impact on physical performance and the logistical challenges associated with implementation remain unexplored.