Background and aim of the review
Delayed onset muscle soreness describes the muscular pain, tenderness and stiffness experienced after high-intensity or unaccustomed exercise. Various therapies are in use to prevent or reduce muscle soreness after exercise and to enhance recovery. One more recent therapy that is growing in use is whole-body cryotherapy (WBC). This involves single or repeated exposure(s) to extremely cold dry air (below -100°C) in a specialised chamber or cabin for two to four minutes per exposure. This review aimed to find out whether WBC reduced muscle soreness, improved recovery and was safe for those people for whom it can be used.
Results of the search
We searched medical databases up to August 2015 for studies that compared WBC with a control intervention such as passive rest or no treatment; or with another active intervention such as cold water immersion. We found four small studies. These reported results for a total of 64 physically active young adults. All but four participants were male. The studies were very varied such as the type, temperature, duration and frequency of the WBC and the exercises used to induce muscle soreness. There were two comparisons: WBC compared with a control intervention; and WBC compared with far-infrared therapy.
Key results
All four studies compared WBC with either passive rest or no treatment. These provided some evidence that WBC may reduce muscle soreness (pain at rest) at 1, 24, 48 and 72 hours after exercise. However, the evidence also included the possibility that WBC may not make a difference or may make the pain worse. There was some weak evidence that WBC may improve well-being at 24 hours. There was no report and probably no monitoring of adverse events in these four studies.
One very small study also compared WBC with far-infrared therapy and reported lower levels of muscle soreness one hour after the treatment.
Quality of the evidence
All four studies had aspects that could undermine the reliability of their results. We decided that the evidence was of very low quality for all outcomes. Thus, the findings remain very uncertain and further research may provide evidence that could change our conclusions.
Conclusions
The currently available evidence is insufficient to support the use of WBC for preventing and treating muscle soreness after exercise in adults. Furthermore, the best prescription of WBC and its safety are not known.
There is insufficient evidence to determine whether whole-body cryotherapy (WBC) reduces self-reported muscle soreness, or improves subjective recovery, after exercise compared with passive rest or no WBC in physically active young adult males. There is no evidence on the use of this intervention in females or elite athletes. The lack of evidence on adverse events is important given that the exposure to extreme temperature presents a potential hazard. Further high-quality, well-reported research in this area is required and must provide detailed reporting of adverse events.
Recovery strategies are often used with the intention of preventing or minimising muscle soreness after exercise. Whole-body cryotherapy, which involves a single or repeated exposure(s) to extremely cold dry air (below -100 °C) in a specialised chamber or cabin for two to four minutes per exposure, is currently being advocated as an effective intervention to reduce muscle soreness after exercise.
To assess the effects (benefits and harms) of whole-body cryotherapy (extreme cold air exposure) for preventing and treating muscle soreness after exercise in adults.
We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, the British Nursing Index and the Physiotherapy Evidence Database. We also searched the reference lists of articles, trial registers and conference proceedings, handsearched journals and contacted experts.The searches were run in August 2015.
We aimed to include randomised and quasi-randomised trials that compared the use of whole-body cryotherapy (WBC) versus a passive or control intervention (rest, no treatment or placebo treatment) or active interventions including cold or contrast water immersion, active recovery and infrared therapy for preventing or treating muscle soreness after exercise in adults. We also aimed to include randomised trials that compared different durations or dosages of WBC. Our prespecified primary outcomes were muscle soreness, subjective recovery (e.g. tiredness, well-being) and adverse effects.
Two review authors independently screened search results, selected studies, assessed risk of bias and extracted and cross-checked data. Where appropriate, we pooled results of comparable trials. The random-effects model was used for pooling where there was substantial heterogeneity. We assessed the quality of the evidence using GRADE.
Four laboratory-based randomised controlled trials were included. These reported results for 64 physically active predominantly young adults (mean age 23 years). All but four participants were male. Two trials were parallel group trials (44 participants) and two were cross-over trials (20 participants). The trials were heterogeneous, including the type, temperature, duration and frequency of WBC, and the type of preceding exercise. None of the trials reported active surveillance of predefined adverse events. All four trials had design features that carried a high risk of bias, potentially limiting the reliability of their findings. The evidence for all outcomes was classified as 'very low' quality based on the GRADE criteria.
Two comparisons were tested: WBC versus control (rest or no WBC), tested in four studies; and WBC versus far-infrared therapy, also tested in one study. No studies compared WBC with other active interventions, such as cold water immersion, or different types and applications of WBC.
All four trials compared WBC with rest or no WBC. There was very low quality evidence for lower self-reported muscle soreness (pain at rest) scores after WBC at 1 hour (standardised mean difference (SMD) -0.77, 95% confidence interval (CI) -1.42 to -0.12; 20 participants, 2 cross-over trials); 24 hours (SMD -0.57, 95% CI -1.48 to 0.33) and 48 hours (SMD -0.58, 95% CI -1.37 to 0.21), both with 38 participants, 2 cross-over studies, 1 parallel group study; and 72 hours (SMD -0.65, 95% CI -2.54 to 1.24; 29 participants, 1 cross-over study, 1 parallel group study). Of note is that the 95% CIs also included either no between-group differences or a benefit in favour of the control group. One small cross-over trial (9 participants) found no difference in tiredness but better well-being after WBC at 24 hours post exercise. There was no report of adverse events.
One small cross-over trial involving nine well-trained runners provided very low quality evidence of lower levels of muscle soreness after WBC, when compared with infrared therapy, at 1 hour follow-up, but not at 24 or 48 hours. The same trial found no difference in well-being but less tiredness after WBC at 24 hours post exercise. There was no report of adverse events.