The preferred hangout for the swolest among us these days is a cold plunge. They’ve been touted by athletes and manosphere personalities as a way to supercharge recovery and boost immune system response. For many, notably Steve Aoki, cold plunge tubs are now backyard fixtures.
But scientists just poured some cold water on the practice. A new study from the American College of Sports Medicine found that taking the plunge may undermine your lifting sesh.
Researchers took a dozen guys between the ages of 20 and 28, put them through a resistance training workout, and then had them plunge one leg in 46 degree Fahrenheit/8 degree Celsius water and the other one in body-temp water—picture straddling two upper-thigh-high barrels—for 20 minutes. (Before you @ us, yes, we know that some of you keep your ice-crusted troughs just above freezing, but going that low for the 20 minutes of this study could have caused frostbite.)
Meanwhile, the half-frigid participants were given a protein-carbohydrate beverage to provide muscle-repairing nutrition that also contained a special amino acid. That amino acid acted as a tracer, allowing the researchers to visualize via ultrasound how “food” was reaching muscles. Coupled with muscle biopsies, their research revealed that 30% less nutrition ended up in the cold leg versus the tepid one.
“This is quite a substantial difference,” study author Milan Betz, a researcher in the human biology department at Maastricht University in the Netherlands, tells GQ.
So why does this happen? Cold plunging causes vasoconstriction, which is a fancy way of saying that it closes off blood flow. If you’ve ever heard of people using cold capping to avoid hair loss during chemo, it’s the same mechanism. Nutrients travel through the bloodstream to muscles damaged through exercise, allowing those muscles to repair and get stronger. If that stream is constricted, it’s harder to reach the muscles immediately after a workout.
Yes, protein synthesis (how muscles repair themselves) continues over the course of a day or two, but those few hours following a workout are especially valuable for rebuilding muscle, Betz says.
Not only that, but plunging also has a cumulative effect. Older research found that people who did a 10-minute cold plunge after resistance training saw less muscle growth after three months versus those on the same workout regimen sans plunge.
“Our main conclusion is that [cold plunging] should be avoided after resistance exercise when muscle building is your main goal,” Betz says.
To be fair, that’s not everyone’s main goal. Endurance athletes such as runners or rowers coming off of a hard workout might want to take the plunge to recover faster so they can exercise effectively the next day. It’s a favorite among some mid-competition athletes who find that the icy depths get them ready to roll more quickly and perform better, some muscle synthesis be damned.
Pros and weekend warriors alike find that cold dips help their mental health, which is a valid reason to get chilled to the bone. And Wim Hof acolytes (as well as some research) will suggest the cold confers immune-boosting properties.
That being said, none of this is settled science, and some research would suggest that cold plunging confers a placebo effect. The bottom line is cold plunging is neither good nor bad. You have to figure out whether it’s serving your particular workout and wellness goals.
Can you have your high-protein, low-carb, refined sugar- and seed oil–free cake—and eat it too? In other words, is there an exact amount of time you can plunge that won’t affect protein synthesis? Maybe, but scientists don’t have an exact number.
“Already after five minutes, you can see a clear drop in muscle temperature, which may already result in some of the effects we saw in our study,” Betz says. “I would speculate that one or two minutes would not result in clear negative effects. Still, if the goal is to maximize muscle growth, I would play it safe and avoid it altogether.”
