Taking a cold bath after exercise can soothe sore muscles but it is unclear whether this is safe, say experts.
Plunging into chilly water can provide a shock to the system and may even be harmful, researchers at the UK Cochrane Centre warn.
After looking at available trial evidence - 17 small studies involving 366 people - they say there is not enough evidence to back the technique.
There may well be other better ways to ease muscular aches, they suggest.
This might include a spot of light jogging or a dip in a warm bath, they say.
The idea behind submerging the muscles in icy water, sometimes referred to as cryotherapy, is to reduce swelling and the associated stiffness and soreness that comes with working the muscles hard.
The trend started in elite level sport, but it is becoming increasingly popular amongst amateur athletes too.
Comedian Eddie Izzard, who last year ran 43 marathons in 51 days to raise money for charity, said his daily ice baths were a necessary evil to stop his "legs inflating to twice the size of an elephant".
In the studies that the Cochrane team looked at, participants were asked to get into a bath or container of cold water after running, cycling or resistance training.
In most trials, participants spent between five and 24 minutes in water that was 10-15C, although in some cases much colder temperatures were used or participants were asked to get in and out of the water a number of times.
Lead researcher Dr Chris Bleakley, of the University of Ulster, Northern Ireland, said: "We found some evidence that immersing yourself in cold water after exercise can reduce muscle soreness, but only compared to resting or doing nothing."
But there were too few studies that compared cold baths with other interventions to say that it is the best strategy for sore limbs.
And safety concerns remain unanswered.
Dr Bleakley said: "It is important to 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."
Leonie Dawson, professional adviser to the Chartered Society of Physiotherapy, said: "This isn't advisable for everyone. If someone had an underlying heart condition then the shock could be damaging.
"And for anybody with Raynaud's - a problem of the circulation - it would have a devastating effect on them."
She said it would also be important to ensure that the water was clean for hygiene reasons: "Some rugby clubs have a wheelie bin filled with cold water that the players will use one after the other, even if they have open cuts and injuries from the playing field."
She said, generally, applying something cool on the skin to reduce pain and swelling was safe.
"It makes up part of the PRICE guidelines - Protect, Rest, Ice, Compression and Elevation - for managing soft tissue injury.
"But it is worth remembering that some of those gel ice packs you can get go down to temperatures of minus 20 and if you go to sleep with them on you can get a rather nasty ice burn."