Are the Benefits of Cold Plunges and Cryotherapy Just a Placebo Effect?

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Cold-water immersion is a post-exercise modality purported to enhance physical recovery following strenuous exercise, and people certainly report feeling less sore, less fatigued, and more recovered after cold plunging. But the vast majority of cryotherapy studies have been conducted using a do-nothing control group, like just sitting in a chair, and have not taken expectancy effect or treatment belief into account––meaning maybe the cold plunge only works because people think it works. In other words, could it just be the placebo effect? Practitioners didn’t just feel better, though; in some cases, they performed better too. But that also could be a placebo effect. Give athletes placebos, and there aren’t only effects on perceived exertion, for example, but on actual muscle power, running speed, and even heart rate. Placebos, like sugar pills, that are deceptively claimed to be some performance-enhancing drug actually enhance performance.

Or, give one set of people a capsule of cornstarch and say it’s going to make them run faster, and another set of people the same capsule and tell them it’s going to make them run slower, and, you guessed it: the it-will-make-you-faster group ran faster, and the it-will-make-you-slower group ran slower.

Give people a sugar pill and tell them it’s a strong combination of amino acids with immediate effects on strength, and they magically leg and bench press more—until they were informed they were lied to, and learn it was just a sugar pill. And just like that, their performance enhancement disappeared.

You can even get a dose-response effect. When people were told they were getting about 300 mg of caffeine, 600 mg of caffeine, or a placebo, even though everybody got placebos, the ones who were told they got the placebo did worse. And there was increased power in the lower fake-caffeine group, and even more in the higher fake-caffeine group, with all the fake-caffeinated participants even reporting caffeine-related side effects. Once people are told they are taking a substance that will enhance performance, all sorts of things kick in: belief, pain sensation, expectancy, and arousal––all of which may impact performance. No wonder there’s a gazillion-dollar sports supplement market selling tons of drinks, powders, and supplements. They may work, but maybe not any better than a sugar pill, which would certainly be a lot cheaper.

For cold-water immersion, it’s difficult to administer a true placebo. But researchers cited a study that did include a placebo treatment, and the effect of cold-water immersion was found to be no bigger than the placebo effect. There have actually been five such studies to date.

Here’s the one they were referring to. Thirty guys performed an acute high-intensity interval training session, comprised of four 30-second sprints, immediately followed by one of the following three 15-minute recovery conditions: cold-water immersion (10.3°C ± 0.2°C, about 50 degrees Fahrenheit), a warm, near-body temperature water immersion placebo, or a warm, near-body temperature water-immersion control group. Hold on. What’s the difference between the placebo group and the control group? In the placebo group, the researchers squirted something in the water (actually just some soap), and led the participants to believe it had special recovery enhancement properties.

Here’s how everyone did in terms of recovery of muscle strength, measuring maximal voluntary isometric contraction strength, both peak and average. Here’s how the cold-water immersion did, and here’s how the warm immersion with the fake ergogenic soap did––significantly better than just the plain warm-water group. This study demonstrated that influencing one’s belief in the efficacy of warm-water immersion as an ergogenic aid in recovery can account for an approximate 13 percent improvement in muscle strength 48 hours after high-intensity exercise. So, it’s important for coaches and sports scientists alike to educate their athletes on the benefits of recovery, and to also encourage belief in the practice. Wait, are they encouraging them to lie to athletes? Hey, if that lie is going to increase performance by 13 percent.

Here are the other four placebo-controlled cold-plunge studies. Cold-water immersion offers no functional or even perceptual benefit compared to a sham intervention during an eight-week resistance training program. Here, researchers told people in the control group that their protein supplements were tweaked. And that was enough to completely eliminate any significant effect, and had the training program gone longer, they would expect the cold-immersion group to actually shrink long-term gains in muscle mass, or strength, or both.

The next was cold-water immersion after a soccer match, randomized to cold plunge, passive rest recovery, or a “recovery” beverage, which was just a placebo. And both the cold plunge and placebo were more effective than the rest condition. Doing something made people feel better than doing nothing, but the cold plunge did no better than the fake beverage––demonstrating that indeed, cold-water immersion reduces muscle soreness. But this beneficial effect was a manifestation of the placebo effect.

What about whole-body cryotherapy—like sitting in a cryochamber at 100° below zero F (-73°C)—versus cold plunge or placebo after resistance exercise? Neither cryotherapy intervention was more effective than the placebo treatment at accelerating recovery, neither was more effective as a pill of cornstarch, as long as you tell people the cornstarch pill is a branched-chain amino acid supplement. Oh my God – are athletes that gullible? No wonder these supplement companies make off like bandits. The majority of group comparisons revealed unclear, trivial, or unfavorable effects of cryotherapy compared to the placebo intervention––meaning in some ways, the magical cornstarch pill worked better, contradicting much of the previous literature. But that’s because much of the previous literature compared cold-water immersion to nothing, just like sitting in a chair.

And finally, recovery following a marathon: a comparison of cold-water immersion, whole-body cryotherapy, and a placebo control group given a fake tart-cherry juice beverage. Neither cold treatment, whether wet or dry, was more effective than a placebo at improving functional recovery or perceptions of training stress following a marathon. In fact, the placebo worked even better, cold water worked better than the cryotherapy, but they both did worse than the fake fruit-flavored drink. These findings lend further evidence to suggest that treatment belief and the placebo effect may be largely responsible for the beneficial effects of cryotherapy on recovery.

But what about the objective drop in muscle damage indicators after cold water immersion? It’s been reasoned that reducing muscle temperature and blood flow may dampen the local inflammatory response, and thereby boost post-exercise recovery. What is striking is the assumption that inflammation needs to be dampened or suppressed. Isn’t inflammation a crucial component of the adaptive response of skeletal muscle to training? And, cold plunges aren’t actually anti-inflammatory. Where did we even get that idea from? It was from studies on lab animals with induced gross muscle injuries, which isn’t exactly the same as just exercising strenuously.

Okay, but there’s still that reduced muscle damage, even if doesn’t affect inflammation or muscle function recovery. But doesn’t exercise-induced muscle damage play a role in skeletal muscle growth? Might dampening the damage be throwing cold water on muscle growth? We’ll find out, next.

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