Ergogenic effects of precooling with cold water immersion and ice ingestion: A meta‐analysis

This review evaluated the effects of precooling via cold water immersion (CWI) and ingestion of ice slurry/slushy or crushed ice (ICE) on endurance performance measures (e.g. time‐to‐exhaustion and time trials) and psychophysiological parameters (core [Tcore] and skin [Tskin] temperatures, whole body sweat [WBS] response, heart rate [HR], thermal sensation [TS], and perceived exertion [RPE]). Twenty‐two studies were included in the meta‐analysis based on the following criteria: (i) cooling was performed before exercise with ICE or CWI; (ii) exercise longer than 6 min was performed in ambient temperature ≥26°C; and (iii) crossover study design with a non‐cooling passive control condition. CWI improved performance measures (weighted average effect size in Hedges’ g [95% confidence interval] + 0.53 [0.28; 0.77]) and resulted in greater increase (ΔEX) in Tskin (+4.15 [3.1; 5.21]) during exercise, while lower peak Tcore (−0.93 [−1.18; −0.67]), WBS (−0.74 [−1.18; −0.3]), and TS (−0.5 [−0.8; −0.19]) were observed without concomitant changes in ΔEX‐Tcore (+0.19 [−0.22; 0.6]), peak Tskin (−0.67 [−1.52; 0.18]), peak HR (−0.14 [−0.38; 0.11]), and RPE (−0.14 [−0.39; 0.12]). ICE had no clear effect on performance measures (+0.2 [−0.07; 0.46]) but resulted in greater ΔEX‐Tcore (+1.02 [0.59; 1.45]) and ΔEX‐Tskin (+0.34 [0.02; 0.67]) without concomitant changes in peak Tcore (−0.1 [−0.48; 0.28]), peak Tskin (+0.1 [−0.22; 0.41]), peak HR (+0.08 [−0.19; 0.35]), WBS (−0.12 [−0.42; 0.18]), TS (−0.2 [−0.49; 0.1]), and RPE (−0.01 [−0.33; 0.31]). From both ergogenic and thermoregulatory perspectives, CWI may be more effective than ICE as a precooling treatment prior to exercise in the heat.