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- Alex Hutchinson (@sweatscience)
Post-workout ice baths are one of those things that everyone believes in, no matter what the science says. There have been a bunch of ice bath studies, but they’ve used lots of different water temperatures, immersion times, and outcome measures, and the results have been very mixed. This month’s European Journal of Applied Physiology has a study from France’s National Institute of Sport that looks like the strongest evidence yet in favour of ice baths — and offering some concrete advice on water temperature and immersion time.
One key difference from previous studies: they used elite athletes — 41 football, rugby and volleyball players — whose recovery might be expected to be faster than untrained volunteers. They tested four different protocols:
- TWI: body-temperature water (36 C) for 15 minutes;
- CWI: cold water (10 C) for 15 minutes;
- CWT: contrast water (10 C and 42 C), alternating 90-second bouts for 15 minutes;
- PAS: no water — just sitting there for 15 minutes.
The exercise they used to induce fatigue and muscle damage was alternating bouts of hard rowing and counter-movement jumps. They took blood samples and tested muscle strength (MVC), jump height, and power produced during 30 seconds of rowing — and they did those tests before and immediately after the exercise, then again one hour and 24 hours later.
As you can imagine, with all those different test groups and protocols, the results are a bit of a jumble. The key result, as far as I’m concerned, is right here:
This is the data for creatine kinase, which is a commonly measured marker related to muscle damage. Its exact significance is often debated, but the authors of this study suggest it’s a sign of “reduced passive leakage from disrupted skeletal muscle, which may result in the increase in force production during ensuing bouts of exercise.” The key: the ice bath outperforms all the other interventions, including the contrast bath.
Of course, nothing is quite that simple. If we look at the performance measures, the picture gets muddier:
What we’re interested in here is the cases where performance returns to “normal” quickly. The asterisks indicate where performance is reduced from the first bout by a statistically significant amount. The broad conclusion we can draw is that both the ice bath and the contrast bath seem to offer some advantages compared to room temperature water or not bath. The main reason I included this data is to show that it’s not a simple, magical effect. It’s complicated. But for practical purposes, this data gives me more confidence than any previous study to support the very strong anecdotal evidence that a sustained cold-water bath — in this case, 15 minutes at 10 C — helps to speed up recovery after hard workouts.