In the last decade, cold-water immersion has emerged as one of the most popular post-exercise recovery strategies utilized among athletes during training and competition. This primarily stems from the belief that cold-water immersion facilitates aspects of recovery and regeneration, thereby conferring a potential training and performance advantage. But is it a friend, foe, or just futile?
The cold truth…is that local cryotherapy, meaning like an ice pack, does not appear to diminish soreness or accelerate the recovery strength. Local cryotherapy does not seem to contribute to the improvement of delayed onset muscle soreness or muscle weakness associated with exercise-induced muscle damage. But what about cold plunges?
If you look at the largest systematic review and meta-analysis of the effects of cold plunges on the recovery of physical performance, compiling the results of more than five dozen randomized, controlled, or crossover studies, after cold-water immersion, people felt less sore after a workout, at one hour later, six hours later, one day, two days, and three days later––but not after four days. They also felt less fatigued—particularly in the hour or hours immediately afterwards. And, after three days, they reported feeling more recovered than those who hadn’t done the cold plunges. But were they actually more recovered using objective measures?
Endurance was significantly improved an hour later, but not after that. Jump performance was impaired six hours after the cold plunge, but was significantly improved 24 hours later. \ If we put all the studies together, there may be a small benefit favoring cold plunges. But only about one in five found statistically significant benefit, one found harm, and the vast majority found no significant effect. Still, enough of the studies leaned in the direction of benefit to tip the scale.
In terms of sprint performance, there was an initial deterioration in performance, but then none after that, and a significant increase in strength recovery the next day. This coincides with a lessening of muscular damage indicators the next day, lasting through days two and three.
What are the best parameters of cold plunges in terms of timing, temperature, and duration? There really isn’t a “gold standard,” but the first systematic review concluded that cold-water immersion at a temperature between 11 and 15 °C for 11–15 minutes was best. That’s like in the 50s Fahrenheit. However, since that first review, there’s been a bunch more studies, and the updated review found that the water temperature didn’t seem to matter, whether severely cold at 5 to 9 degrees Celsius (in the Fahrenheit 40s), or moderately cold at 10 to 15 degrees °C. But the immersion duration did seem to matter. Immersions lasting less than 10 minutes presented better results, and plunging for more than 16 minutes didn’t seem to help at all. And it’s better to immerse immediately following exercise rather than waiting.
Now in most of these studies, researchers used passive recovery in the control groups––meaning people were randomized to cold plunges, or to just like sit in a chair for 20 minutes. But who exercises intensely and then just sits in a chair? Many athletes use active recovery in the form of a low-intensity “warm down” to recover after exercise––like walking around a bit to keep the blood flowing, getting rid of some of that lactic acid buildup. So instead, what about randomizing people to cold-water immersion versus normal active recovery? That might be a fairer comparison. And in that case, the cold plunge didn’t work. It was no more effective than active recovery. Okay, but that’s just one study.
Let’s look at a meta-analysis of all such studies comparing the effects of cold‐water immersion with other recovery modalities. In terms of muscle soreness, cold-water immersion didn’t seem to work any better than active recovery, or any of the other recovery methods, including warm-water immersion. Same for the recovery of muscular power. No significant difference between cold plunging and active recovery, contrast water therapy (which is like alternating hot and cold), warm-water immersion, air cryotherapy, (like in a cryochamber), massage, or electrical stimulation. If it’s all the same, I think I might prefer the massage to the plunge. Same for the recovery of muscle strength—no difference. Immersing in cold water did seem to beat out warm water on perceived recovery, though, but nothing else. And it was the same with flexibility––no difference. And the same with measures of muscle damage, though electrifying your legs did seem to work better than the cold water.
The bottom line is that all the recovery methods seem to achieve about the same. So, a cold plunge may be better than just sitting down after intense exercise, but there’s a wide range of other practices that appear to be just as effective. But any time doing something beats out doing nothing; you always have to ask if it might just be a placebo effect. You don’t know if the perceived benefits of cold plunges are all in your head until you put it to the test with a placebo-controlled trial. But how do you even do that? We’ll find out, next.
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 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.
In my last video, I talked about how the benefits of cold plunges appear to be due to the placebo effect. But cold-water immersion isn’t just futile but may be a foe when it comes to our muscle mass. A key take-home message is that if the goal of training is to build muscle mass and strength, regular cold plunges after exercise may not be beneficial.
It all started with this study in 2006, showing that cold-water immersion of muscles may actually interfere with regenerative processes, and retard rather than support the desired improvement of muscular performance. Since then, independent corroborating evidence has continued to accumulate that post-exercise cooling diminishes muscle adaptations to strength training, leading to punny click-bait titles like “Cryotherapy: Are we freezing the benefits of exercise?”, “Is the ice bath finally melting?”, “The cold truth”, “Cooling down the use of cryotherapy.”
Here’s a typical study showing that cold plunges substantially attenuate long-term gains in muscle mass and strength. Twelve weeks of strength training with just typical active recovery led to a significant increase in muscle mass in the quads, but the same amount of training with cold plunges barely moved the needle. And this manifested in significantly less strength, whether we’re talking maximum leg press strength, knee extension, isometric torque, or rate of force development.
Note that smaller muscles don’t necessarily lead to less strength. In this study, the blunted muscle fiber growth didn’t translate to impaired strength development, but post-exercise cold plunges should be avoided if you do actually want bigger muscles. But there are folks, like long-distance runners, who may not want that extra bulk; so, cold plunges may be a way to keep their muscles smaller.
This is probably the most rigorous study involving measuring muscle mass using the gold standard––MRI imaging––and actually taking muscle biopsies before and after. And, while both groups gained muscle mass and strength following training, these gains were significantly smaller in the cold-water immersion group compared with the active recovery group. And the cross-sectional area of fast-twitch muscle fibers also increased only in the control group.
There have been all sorts of published points and counterpoints about the cold-water dampening effect on hypertrophy gains. Here’s a systematic review with meta-analysis of all such studies. A harmful effect of cold-water immersion was verified for every single strength parameter measure: one-rep maximum, maximal isometric strength, strength endurance, and ballistic efforts all reduced by cold plunges. So, it appears useless for endurance training and deleterious for strength training. Why are people still doing it? Here’s a 2024 meta-analysis, and the title says it all: Throwing cold water on muscle growth.
This may be because cold water immersion puts the chill on muscle protein synthesis, both in the hours immediately following exercise and during weeks of strength training. Another explanation for cold-induced reductions in strength is that cold-water immersion constricts the arteries and causes a reduction in blood flow, which is important for muscle strength and development. A 50 percent drop in femoral blood flow compared to warmer water or control. Reductions in muscle blood flow reduces the oxygen supply, which plays a role in the decreased muscle mass, too. Cold plunges also blunt the testosterone response. So, the impaired testosterone response may be another reason for the attenuated strength and muscle growth.
So, cold plunges following resistance exercise sessions should be discouraged, but they are said not to impair aerobic training. That’s not always the case, though, as some studies show a reduction of aerobic fitness as well. This study found that muscle warming was better than cooling, thought due to the slowing of glycogen resynthesis in the cold. Mean power output was better preserved hours after an all-out arm-cycling exercise. The cold did worse than control, and after the muscle heating, there was hardly any decrease in power output at all?
So, wait, should we instead be like taking a warm bath or sauna after exercise instead of an ice water bath? Regardless, cryotherapy is apparently not as cool as it seems.
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