Abstract: Seventeen small trials were included, involving a total of 366 participants. Study quality was low. The temperature, duration and frequency of cold-water immersion varied between the different trials as did the exercises and settings. The majority of studies failed to report active surveillance of pre-defined adverse events. Fourteen studies compared cold-water immersion with passive intervention. Pooled results for muscle soreness showed statistically significant effects in favour of cold-water immersion after exercise at 24 hour (standardised mean difference (SMD) -0.55, 95% CI -0.84 to -0.27; 10 trials), 48 hour (SMD -0.66, 95% CI -0.97 to -0.35; 8 trials), 72 hour (SMD -0.93; 95% CI -1.36 to -0.51; 4 trials) and 96 hour (SMD -0.58; 95% CI -1.00 to -0.16; 5 trials) follow-ups. These results were heterogeneous. Exploratory subgroup analyses showed that studies using cross-over designs or running based exercises showed significantly larger effects in favour of cold-water immersion. Pooled results from two studies found cold-water immersion groups had significantly lower ratings of fatigue (MD -1.70; 95% CI -2.49 to -0.90; 10 units scale, best to worst), and potentially improved ratings of physical recovery (MD 0.97; 95% CI -0.10 to 2.05; 10 units scale, worst to best) immediately after the end of cold-water immersion. Five studies compared cold-water with contrast immersion. Pooled data for pain showed no evidence of differences between the two groups at four follow-up times (immediately, 24, 48 and 72 hours after treatment). Similar findings for pooled analyses at 24, 48 and 72 hour follow-ups applied to the four studies comparing cold-water with warm-water immersion. Single trials only compared cold-water immersion with respectively active recovery, compression and a second dose of cold-water immersion at 24 hours. There was some evidence that cold-water immersion reduces delayed onset muscle soreness after exercise compared with passive interventions involving rest or no intervention. There was insufficient evidence to conclude on other outcomes or for other comparisons. The majority of trials did not undertake active surveillance of pre-defined adverse events. High quality, well reported research in this area is required.

Plain-language summary: Our review included 17 small trials, involving a total of 366 participants. Study quality was low. Fourteen trials compared cold-water immersion applied after exercise with 'passive' treatment involving rest or no treatment. The temperature, duration and frequency of cold-water immersion varied between the different trials as did the exercises and settings. There was some evidence that cold-water immersion reduces muscle soreness at 24, 48, 72 and even at 96 hours after exercise compared with 'passive' treatment. Limited evidence from four trials indicated that participants considered that cold-water immersion improved recovery/reduced fatigue immediately afterwards. Most of the trials did not consider complications relating to cold-water immersion and so we cannot say whether these are a problem. There were only limited data available for other comparisons of cold-water immersion versus warm or contrasting (alternative warm/cold) water immersion, light jogging, and compression stockings. None of these showed important differences between the interventions being compared. While the evidence shows that cold-water immersion reduces delayed onset muscle soreness after exercise, the optimum method of cold-water immersion and its safety are not clear.