Does cold water immersion help muscle recovery after a workout?
What is cryotherapy?
If you’ve watched the 2012 summer Olympics, as I’m sure most of us have, you’ve probably seen some of the world’s most elite athletes head straight for an ice cold bath right after they compete. You saw it most often among the swimmers, but many other types of athletes will do the same. Why do they do it?
The practice is called cryotherapy, or cold water immersion, and the belief is that cold water immersion immediately after exercise can help to prevent delayed onset muscle soreness, or DOMS.
Lactic Acid and DOMS
You might have heard that lactic acid buildup in the muscles is a cause of delayed onset muscle soreness. Actually, that’s incorrect.
Lactic acid will form as a result of a hard workout, but the lactic acid which is produced is also removed from the muscles very quickly as blood circulates through them. The blood carries nutrients to the muscles and takes away waste products like lactic acid. In fact, it takes away lactic acid very quickly. By the time an hour has gone by since the end of your workout, almost all of the lactic acid will have been removed.
Therefore, because DOMS occurs one to three days after a workout and lactic acid buildup is already gone within a couple of hours post-workout, lactic acid can't be the culprit.*
How does cryotherapy work?
The principle behind cryotherapy is very similar to the principle behind applying an ice pack to an injury like a sprained ankle or a pulled muscle. The cold causes vasoconstriction, or the narrowing of blood vessels, which in turn reduces inflammation. If inflammation is one of the factors in DOMS, reducing it should help prevent delayed onset muscle soreness.
After the cold water immersion, the theory continues, the more vigorous returned blood flow to the muscle should help bring more nutrients to the muscle and dispose of waste which might contribute to the inflammation.
Does cold water immersion work? And is it safe?
In a nutshell, nobody is completely sure.
There is a lot of anecdotal evidence about cryotherapy, but there have been very few actual experiments done to establish a relationship between cold water immersion and the reduction of delayed onset muscle soreness. Furthermore, all of those experiments appear to have been small scale, which gives us a very limited amount of information to go on.
To understand the data, I turned to a recent meta-study – that is, an analysis of the data gathered from several other experimental studies – done by the University of Ulster in February of 2012.**
In it, the researchers searched the literature and selected 17 experiments which had been conducted over the period from 1998 to the present day. Among other things, they searched for experiments which specifically studied cold water immersion and its effects on delayed onset muscle soreness, eliminating those with incomplete data or with confounding factors such as patients with pre-existing injuries or conditions.
Collectively, these 17 experiments studied the effects of cryotherapy on DOMS in 366 subjects. However, teasing out a definitive conclusion was difficult due to wide variations in experimental technique.
For instance, the temperature of the cold water immersion was not consistent across the experiments. Temperatures tested ranged from 5 to 15 Celsius. If you don't test the same temperature, how do you know which temperature is the one that does the trick?
Immersion times also differed, ranging all the way from 5 to 24 minutes, with an average immersion time of 12.6 minutes. Again, as with temperature, if you don't test the same duration of immersion, how do you know which duration works?
Types of exercise also differed. In 9 of the experiments, only resistance training was performed. In the other 8 experiments, running and cycling were performed. DOMS is more likely to occur – and likely to be more severe – after resistance training. It can occur after an intense cardio session, but when you combine the decreased likelihood of DOMS after running or cycling with the fact that the patients in the running and cycling experiments were physically fit, unlike those in the resistance training experiments, you end up with fewer instances of DOMS to measure. This might have been another confounding factor.
All of that is to say that, as far as testing the effects of cryotherapy on muscle recovery goes, there have been a limited number of experiments performed on a limited number of people with a wide variety of parameters, which make it very difficult to get a clear picture of the actual effects.
However, once the researchers at the University of Ulster had compiled their data, they were able to reach two fundamental conclusions:
1. "In the case of cold water immersion (defined as immersion in water below 15 degrees Celsius for at least one minute) versus passive intervention/rest: “Cold-water immersion [performed immediately after a workout] resulted in significantly greater improvements in muscle soreness. "
2. “While the evidence shows that cold-water immersion reduces delayed onset muscle soreness after exercise, the optimum method of cold-water immersion and its safety are not clear.”
So, putting this all together, what do these results mean?
Never, ever soak in 50 degree (Fahrenheit) water for more than very short periods. An immersion of one hour in 50 degree water is enough to cause death from hypothermia. DO NOT DO IT. EVER.
If you want to soak in water that cold, limit your stay to five minutes, NO MORE. I can't emphasize this enough. We both want you to feel better, not to end up in a hospital.
Summary: Should I try cryotherapy to prevent or reduce delayed onset muscle soreness?
Translated from researcher-ese, the University of Ulster study’s conclusions can probably be summed up this way:
Okay, so some people saw a benefit and nobody died, so it’s probably not going to kill you, but we’re not really sure what’s the best way to do it and we can’t say with 100% certainty that it won’t somehow do something moderately bad to you, so be careful. Also, could somebody out there do a decent large-scale study, because this data sucks.
In other words, if you’re worried about DOMS and your choices are between doing nothing or taking a cold bath after your workout, taking a cold bath immediately after your workout will probably be a good preventative measure. It might even help you feel more refreshed and less fatigued, though there appears to be no physical, clinically-testable reason for that. It’s just psychological.
However, none of the experiments studied actually looked at short- or long- term effects of this stuff, so no one can say with any certainty whether there might be negative effects. Nobody got hurt during the experiment, but the researchers didn't follow up on the subjects' health after the experiment was over. So be a little careful.
Also, because the experiments were all over the place in regards to the time spent immersed and the temperature of the water, it’s not clear what method of cold water immersion is most effective. Five minutes? Half an hour? Ice cold water? Cool water? No one really knows for sure.
What is probably true is that short durations of 3 to 5 minutes in water at 15 degrees Celsius, or 59 degrees Fahrenheit, did show positive benefits and are reasonably safe.
Therefore, if you want to safely try cryotherapy with a reasonable expectation of getting results, try it:
1. Immediately after your workout.
2. In cold but not ice cold water, i.e. around 15 degrees Celsius or 59 degrees Fahrenheit.
3. For no more than three to five minutes.
Overall, the data indicates that careful use of cold water immersion might help and probably won't hurt.
Just don't fall asleep in the tub, because hypothermia never did anyone any good.
*Kokkinos, Peter. Physical Activity and Cardiovascular Disease Prevention, pg 111. Sudbury, MA: Jones and Barlett Publishers, 2010.
**Bleakley C, McDonough S, Gardner E, Baxter GD, Hopkins JT, Davison GW. “Cold-water immersion (cryotherapy) for preventing and treating muscle soreness after exercise. “ The Cochrane Library. Issue 2, (2012).