Starting in the 1990s, ice baths gained a reputation for their near-magical ability to accelerate the recovery of sore muscles after workouts. Pro teams installed sophisticated tubs that circulate water at a precisely controlled temperature, usually between 10 C and 15 C; the rest of us dumped trays of ice cubes into our bathtubs.
Then, around 2010, a backlash started. If ice baths reduce post-workout inflammation and cellular stress, critics argued, then in doing so they might be reducing the very signals that tell our muscles to adapt and get stronger. An ice bath, in other words, might retroactively turn a 60-minute run into a 45-minute jog – which would feel good the next day, but defeat the purpose of having run that far in the first place.
Over the past few years, studies have volleyed this debate back and forth without settling it. Now, a pair of new studies add further twists to the argument – and help make the case that the real questions for ice-bath use isn't should I or shouldn't I, but rather when, why and for whom.
The first and most befuddling study, published last month in the Journal of Physiology by researchers in Australia, New Zealand, Norway and Japan, used muscle biopsies and blood tests to check how cellular markers of inflammation changed in the 48 hours after a workout.
The surprising result: A 10-minute ice bath at 10 C starting five minutes after a 45-minute lower-body strength training workout didn't produce any change in inflammatory markers compared with doing the same workout with a 10-minute cool-down on an exercise bike afterward. So whatever effects – good or bad – ice baths may have, they're not the result of reduced inflammation. That doesn't mean ice baths don't do anything at all. As the researchers, led by Jonathan Peake of the Queensland University of Technology, point out, ice baths have other effects that could influence recovery, such as changing muscle temperature and reducing blood flow. And dozens of other studies have found that ice baths do at least reduce how sore athletes feel.
The second study, published last month in the European Journal of Applied Physiology, has better news for ice-bath fans. Researchers at Liverpool John Moores University in Britain found that a 10-minute ice bath after a 45-minute interval running workout enhanced the cellular responses that contribute to the formation of new mitochondria and blood vessels in muscle – two of the key adaptations triggered by endurance exercise.
This finding echoes two previous studies that found ice baths might enhance endurance adaptations. And it contrasts sharply with studies of strength training, including one by Peake's group that found smaller strength increases in subjects who took an ice bath following resistance workouts over a 12-week period.
It's tempting, then, to see a new pattern: Ice baths are good for endurance athletes and bad for strength athletes. But that, too, is probably an oversimplification, says Robert Allan, a researcher at Liverpool John Moores and co-author of the new study.
"Recovery is multifaceted and not completely reliant on a single variable," he says. For example, what you lose in one type of cellular adaptation might be outweighed by what you gain from another type, or from feeling less pain in your next workout or competition. And recovery in contact sports such as hockey may be different again – after all, no one would argue that the soreness caused by a bruising body-check is somehow useful.
Shona Halson, the senior recovery physiologist at the Australian Institute of Sport, recently tried to make sense of the morass of conflicting findings and came up with a list of factors to consider before using ice baths. For example, if you're participating in a contact sport, then ice baths are more likely to be helpful. Similarly, the steep downhills in trail running require "eccentric" muscle contractions, in which leg muscles lengthen even though you're trying to contract them; the resulting muscle damage is likely to benefit from ice baths.
The most important factor, according to Halson, is timing. If you're focused on short-term goals such as a looming competition, then consider an ice bath; if you're more concerned with long-term goals such as gaining fitness and strength, then skip it.
This same message applies more broadly to other recovery aids such as compression garments, massage and even recovery shakes. They have their place, but more isn't always better. Sometimes, after going to all the trouble of pushing your muscles to exhaustion, it's best to simply let them be tired.
To freeze or not to freeze? Shona Halson, the senior recovery physiologist at the Australian Institute of Sport, suggests considering the following questions before using an ice bath.
"Yes" answers suggest an ice bath is more likely to help; "no" answers suggest it might hurt.
1) Are your goals short-term rather than long-term?
2) Are you competing soon and/or frequently?
3) Does your sport involve impact or eccentric muscle contractions?
4) Are you excessively fatigued or injured?
5) Are environmental temperatures high?
For more information, visit mysportscience.com.
Alex Hutchinson's latest book is Which Comes First, Cardio or Weights?