Earlier this week, Gretchen Reynolds from the New York Times published an article titled “Running a Marathon? Think Hot Tub, Not Ice Bath, Afterward.” The piece reports on a new study out of Sweden, which finds warming muscles after a workout helps recovery better than cooling them.
The conclusion? Skip the ice bath and hit the sauna (it’s Sweden, duh). Except, the science of temperature-based recovery is a whole lot murkier than Reynolds purports.
For starters, the study referenced in the article, published on October 25 in The Journal of Physiology, only uses five subjects—too small a sample size to generalize much of anything in a wider population.
But beyond that, the methodology of the researchers hardly mimics how people train and recover in real life. The five subjects used hand cycles to wear out their arms through, “a series of brief but grueling intervals, followed by 20 minutes of easier but almost non-stop exercise,” Reynolds writes.
Researchers tracked the amount of power each person produced, then on the first visit, had them replenish with carbohydrates immediately after, followed by repeating the exercise. On following visits, they repeated the sessions and the carbs, but for two hours after, their arms were either heated or cooled using special sleeves that can change temperature. Once the sleeves were removed, they were asked to do the workout again. When their muscles were warmed, they performed better than when they were cooled.
This seems like a fairly obvious result. Warm muscles simply perform better when you exercise. That is why it is, literally, called a warmup. But, this study fails to accurately mimic the time people actually spend recovering. Hardly anyone only takes two hours between workouts. The researchers would have been better served waiting 24 to 48 hours before administering the hand-cycle workout again.
Rationally, one of the only accurate results you can draw from this study is that if you are doing a second workout in the day, it’s better to stay warm than to cool off (something Olympic decathletes, swimmers, and athletes that have to exert themselves multiple times in one day already know).
This is all not to say that ice baths are actually better for recovery. There have been many conflicting studies over the past decade examining cold recovery’s efficacy. Research from 2012 had runners complete a workout, then stick one leg in an ice bath and the other out. Researchers found the ice bath did help reduce inflammation—which naturally occurs after the muscle stress induced through activity—which is the whole point of ice baths in the first place. Reduce inflammation, proponents of the technique say, and recovery speeds up.
Yet some research, according to a 2012 article in Runner’s World, suggests that inflammation may actually improve performance and boost muscle growth in the long run, rendering the benefits of ice baths relatively useless.
More recently, a 2017 study calls the inflammation reduction induced by ice baths into question. Led by researchers in Australia, it found that ice baths after strength training in a group of men did not change the muscle composition much more than an easy active recovery.
All of this research indicates two things: 1) you will be sore after a hard workout, which is good because it means you are on the road to getting stronger. 2) The only surefire ways to aid recovery may be replenishing carbohydrates (snack away right after a workout) and time.
Other than that, do what makes you feel the best. If it’s dipping into a high mountain stream after a long trail run? Excellent. If it’s popping in to the Sauna with Sven? Well, then skål!