Plunging into cold water after exercise may be an effective way to reduce muscle soreness, but too little is known about harmful side effects, according to new research by the University of Ulster.

Cold Water Immersion (CWI) is becoming increasingly popular with both elite and amateur athletes who believe that this ice bath technique, sometimes referred to as cryotherapy, reduces muscle inflammation and its ensuing effects.

Dr Chris Bleakley at the Health and Rehabilitation Sciences Research Institute at the Jordanstown campus and a team of researchers set out to assess the strength of clinical evidence about how well this method works and whether there is any evidence of harm.

They carried out a systematic review of Cold Water Immersion interventions published in The Cochrane Library, a prestigious collection of databases in healthcare research.

“Our take home message was that cold water immersion reduces muscle soreness by between 15 and 20 per cent, however this was only when compared to a passive recovery such as resting and doing nothing. While 20% is a significant improvement for elite athletes who need to train intensely every day, non elites should consider that muscle soreness is generally self-limiting and these effects are superfluous unless you need to train at 100 per cent every day,” said Dr Bleakley, the lead author of the study. 

“Furthermore some caution around these results is advisable because the people taking part in the trials would have known which treatment they received, and some of the reported benefits may be due to a placebo response.”

The authors included 17 small trials involving 366 people in their review. Participants were asked to get into a bath or container of cold water after running, cycling or resistance training.

The range of different exercises, temperatures and timings employed by the various studies made it difficult to establish any clear guidelines for safe and effective cold water immersion. There was also a lack of evidence about any harm that could be caused by the intervention, as most studies failed to report ill effects. The authors say higher quality studies are needed.

“Non elite athletes considering this practice should perhaps factor in the time and discomfort associated with cold water immersion,” said Dr Bleakley.

“Based on our results, I don’t think that CWI should be considered as a panacea for recovery in sport – in fact our review showed little difference between CWI, and other popular recovery techniques. There may be better ways to reduce soreness, such as warm water immersion, light jogging or using compression stockings, but we don’t currently have enough data to reach any conclusions about these interventions.

“Until further evidence becomes available, I would urge people who train, elite and non elite alike, to find the recovery strategy that works best for them.

“Athletes should also consider that cold water immersion induces a degree of shock on the body. We need to be sure that people aren’t doing anything harmful, especially if they are exposing themselves to very cold water for long periods.”

A related review by two of the authors - Dr Bleakley and Dr Gareth Davison from the University of Ulster - published in the British Journal of Sports Medicine last year, highlighted some of these systemic effects which include a general effect on the sympathetic nervous system, increased blood pressure, heart rate and catecholamine concentration (adrenaline release).

The authors also found that Cold Water Immersion is associated with a level of oxidative stress and a possible increase in free-radical-species formation (very reactive molecules which can damage surrounding cells).

“The long-term effects of this exposure are not fully understood. Weekend warriors wishing to try this out should probably avoid extreme and frequent immersions, that is, very cold temperatures for prolonged periods and limit usage to immersion in moderate temperatures, around 15ºC, after a tough workout,” added Dr Bleakley.

The study has been published by Wiley-Blackwell in the Cochrane Database of Systematic Reviews, Issue 2, 2012 – these Reviews bring together research on the effects of health care and are considered the gold standard for determining the relative effectiveness of different interventions.