Taking a dip in a tub of cold water after exercising may prevent muscle soreness, but a new look at past research says little is known about its side effects or even how long to stay in the water.
In general, the researchers said there is very little quality research on the topic of so-called cryotherapy, despite the treatment's popularity to prevent or reduce muscle soreness days after exercising.
"It's a typical intervention in sports medicine in the elite arena and the professional arena and it gradually started to filter down," said Chris Bleakley, the study's lead author and a researcher at the University of Ulster in Northern Ireland.
Bleakley and his colleagues collected existing data on 366 people from 17 studies for their report in the Cochrane Library, a publication of the Cochrane Collaboration, an international organization that evaluates medical research.
The researchers found that most of the studies on this topic only looked at a handful of athletes and were poorly designed. The lack of data meant they were only able to draw a significant conclusion from 14 studies that compared cold-water baths to doing nothing or just resting.
In the studies, people were asked to get into a cold-water bath that was about 50 to 60 degrees Fahrenheit after exercising. They stayed in the bath from anywhere between five and 24 minutes.
Overall, the baths lessened the soreness the athletes experienced over the next four days between 15 percent and 20 percent, according to Bleakley.
But he told Reuters Health that it's important for people to know that the improvement was only in soreness. It does not mean the muscle was any stronger.
"It's purely a subjective feeling of less soreness," he said.
And even though the studies, collectively, were able to report some improvement, they were not able to come up with a standard method of treatment.
"If you're looking for the single prescription, it's not available yet. And frankly it's going to be different under different situations," said Dr. Thomas Best, co-director of Ohio State University Sports Medicine, who was not involved in the research.
Best told Reuters Health that the new report does not answer how often an athlete should do the treatment, how long they should stay in the cold water or how long they should wait after they finish exercising.
He added that the average athlete should be careful before they think the results apply to them.
"Most of these studies are done in pretty elite athletes. So, their physiological reserves are probably greater than most people. I think you have to be careful that you don't generalize these conditions to everyone," he said.
Bleakley added that there might be other treatments that work just as well, but there is not enough evidence to compare them. He said they could include massages, stretching and just regular water immersion.
"There are numerous other recovery interventions that are probably not quite as uncomfortable," said Bleakley.
They may be more cost effective, too. Cryotherapy costs can range from the price of filling up a tub with cold water to buying special "cold tub" units that look like a traditional hot tub.
The long-term effects of plunging in and out of bone-chilling water are not well known either.
"I think there still needs to be a degree of caution, especially in the sporting arena where the mantra is the no-pain, no-gain attitude," said Bleakley.