Limiting Rise in Heat Load With an Ice Vest During Elite Female Rugby Sevens Warm-Ups

To determine the effect of wearing a phase-change cooling vest in elite female rugby sevens athletes during (1) a simulated match-day warm-up in hot conditions prior to a training session and (2) a prematch warm-up during a tournament in cool conditions. This study consisted of 2 randomized independent group designs (separated by 16 d) where athletes completed the same 23- to 25-minute match-day warm-up (1) in hot conditions (range = 28.0°C to 35.1°C wet bulb globe temperature [WBGT]) prior to training and (2) in cool conditions (range = 18.8°C to 20.1°C WBGT) prior to a World Rugby Women's Sevens Series match. In both conditions, athletes were randomly assigned to wearing either (1) the standardized training/playing ensemble (synthetic rugby shorts and training tee/jersey) or (2) the standardized training/playing ensemble plus a commercial phase-change athletic cooling vest. Group-wise differences in core temperature rise from baseline, global positioning system-measured external locomotive output, and perceptual thermal load were compared. Core temperature rise during a match warm-up was lower in the hot condition only (-0.65°C [95% confidence interval = -1.22°C to -0.08°C], ηp2=.23 [95% confidence interval = .00 to .51], P = .028). No differences in various external-load variables were observed. Phase-change cooling vests can be worn by athletes prior to, and during, a prematch warm-up in hot conditions to limit excess core temperature rise without adverse effects on thermal perceptions or external locomotion output.