The Benefits of Ice Baths for Runners: The Scientific Evidence of How Long and How Cold Your Ice Bath Should Be
Ice baths are a perennial favorite recovery tactic among college runners who have easy access to a training room. Taking a 10-15 minute dip in icy water is pretty easy when there’s always a tub ready to go. But taking an ice bath is much more of an ordeal for the rest of us who have to fill up, cool down, and hop into a regular bath tub. I’ve even known some dedicated runners living in apartments without tubs who’ve taken ice baths in garbage cans!
But putting that kind of effort into an experience few people describe as pleasant only makes sense if there’s some evidence that it actually helps. So, for that reason, we’ll look at the scientific evidence behind ice baths.
We’ll also try to get a better idea of the specifics of ice bathing: how cold should the water be, and how long should you immerse your legs?
The science of ice baths
Often, training interventions have only a few low-quality studies that analyze their usefulness. Fortunately, cold-water immersion (science-speak for an ice bath) has been the subject of a review by the Cochrane Collaboration, a nonprofit organization of scientists and doctors who support evidence-based medicine. The Cochrane Collaboration puts most of its efforts into reviews on medical care for critical topics like cancer, heart conditions, and pregnancy & childbirth, but some time is also dedicated to more peripheral topics, including exercise-related muscle soreness. In 2012, the Cochrane Collaboration published a lengthy examination of the results of seventeen studies on ice baths.
While the Cochrane Review criticized the small size and low (by medical standards) quality of the studies, they nonetheless found that there was evidence that following intense exercise with cold water immersion reduced muscle soreness over the next several days.
While not the focus of the Cochrane Review, many of the studies also found that taking an ice bath reduced the drop in performance that follows a high-intensity, long-duration effort (like distance running).
However, the review noted that the mechanisms by which ice baths work remain unclear and called for further studies in this area. Most studies in the review used water temperatures between 50 and 59° F and immersion times around 12 minutes.
How water immersion reduces muscle soreness and limit performance drops
Another masterful review on the topic of ice baths and immersion therapy in general was authored by Ian Wilcock, John Cronin, and Wayn Hing at Auckland University of Technology in New Zealand. Their 2006 review focused on how ice baths reduce muscle soreness and limit performance drops in the days following a hard effort.
Interestingly, it seems that much of the benefit comes from the immersion, not the actual temperature.
Immersing yourself in water (of any temperature) introduces a pressure gradient as a result of the weight of the water surrounding your body. The deeper underwater any part of your body is, the greater the pressure. This phenomenon should be familiar to everyone who has ever swum underwater in a pool and felt the pressure in their ears build up at greater depths.
Standing in water will result in a hydrostatic “squeeze” being applied to your legs. During and immediately after a hard workout, fluid from your blood diffuses into your muscles and the blood itself pools in your extremities.The hydrostatic pressure from water immersion counteracts both of these effects: the increased local pressure on the muscles squeezes the fluids back into the blood, and the overall pressure gradient squeezes blood from your legs back towards your core.
The increased exterior pressure also increases the efficiency of your heart, allowing it to move more blood per beat. It’s postulated that these three reactions are why biological markers for fatigue and muscle damage are reduced following cold-water immersion: the water pressure helps clear out waste products and reduces inflammation in the muscles.
The effect of cold temperature
The effects of cold temperature are less well-understood, since only a few studies have contrasted cold water immersion with room-temperature immersion.
However, it is known that cold water immersion reduces the ability of fluids to diffuse into and between muscle cells, which reduces inflammation and so-called “secondary” damage. This is why doctors recommend icing immediately after an acute injury like an ankle sprain, since the damage can be exacerbated by prolonged swelling and inflammation from fluids pooling at the injured site. It is likely that the same prolonged swelling exists (albeit on a smaller scale) inside muscles after long, hard efforts.
Cold water temperatures also decrease nerve impulses, reducing pain from soreness or injury, and for unknown reasons, further reduce the levels of biological markers of muscular damage. It’s not clear whether or not this is indicative of a true reduction in muscle damage.
Are ice baths worth it and how do you use them
Happily, ice baths seem to be a fairly low-tech way of reducing muscle soreness and perhaps avoiding a sharp drop in performance in the days following a long, fast, or particularly hard running workout. While these benefits may reduce injury risk, no studies have looked at whether ice baths can change injury rates.
- Cold temperatures seem to confer some benefit, but the bulk of the advantages of ice baths seem to come from the water pressure, not the temperature. It’s also worth noting that the hydrostatic pressure from standing in a pool, lake, or ocean will be much greater than the pressure from sitting in a fairly shallow tub. So to that end, hopping into a swimming pool or a lake will be almost as good for you as taking a true ice bath.
- More moderate temperatures are also less of a hassle to prepare and endure. But if you do want to take a bona fide ice bath, the ideal temperature range seems to be between 50 and 59° F for somewhere between 10 and 15 minutes. Don’t go much colder than 50° F; you’ll have a much less pleasant experience without any additional proven benefit.
- From what we know so far, it seems that the most effective time to hop into the tub is immediately after you’re done with your workout. Waiting too long will probably diminish the effects of the ice bath, but you also don’t want to cool your muscles off if you plan on doing any strength exercises within an hour or two.