Physiology Friday #267: Using Cold After Exercise Hampers Muscle Gains—Now We Know Why
The downsides of this popular recovery modality.
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There’s a war on ice baths—and ice baths are losing.
In the last few years, we’ve seen pretty damning evidence against the use of post-exercise cold water immersion (CWI). Even though its role as a recovery strategy is supported by the fact that it appears to reduce soreness and support psychological recovery, CWI may blunt the physiological adaptations typically associated with some types of training—primarily strength training.
Several studies have reported attenuated gains in muscle hypertrophy and maximal strength following repeated post-exercise CWI exposure. Meta-analyses suggest small to moderate reductions in key strength-related measures like one-repetition maximum and muscle cross-sectional area (size) among individuals consistently using CWI after resistance training sessions. While the magnitude of these effects is modest, they become increasingly relevant for people seeking maximal muscle gains.
In contrast to its effects on resistance training, CWI does not appear to impair, and may even support, endurance-related adaptations. For example, some studies have shown enhanced activation of signaling pathways involved in mitochondrial biogenesis, particularly through the upregulation of enzymes that regulate aerobic metabolism and mitochondrial proliferation.
However, while increased expression of certain genes and enzymes suggests the potential for augmenting aerobic capacity, actual improvements in fitness or performance don’t necessarily follow. This makes sense to me—I don’t see a reason why post-exercise cold would enhance any adaptation to endurance training.
One of the key research priorities in this area has been investigating how CWI attenuates training adaptations in the context of strength training.
Resistance training relies on acute inflammatory signaling, localized hypoxia, and elevated muscle temperature to drive hypertrophic responses through anabolic signaling pathways such as the mammalian target of rapamycin 1 (mTORC1) and other myogenic regulatory factors. CWI may suppress these signals by lowering muscle temperature and reducing blood flow, thus blunting muscle remodeling.
Skeletal muscle perfusion—the process by which blood delivers oxygen and nutrients and removes waste products from muscle—is a necessary component of exercise training adaptation. If muscles don’t receive adequate blood supply, they can’t receive the growth factors and signals they need to get bigger and stronger. This process also involves the delivery of amino acids from protein—the building blocks of muscle—into skeletal muscle so they can be incorporated into muscle protein and used for muscle protein synthesis. That’s how muscles grow bigger and stronger with training.
As it turns out, getting into cold water after a workout dampens these processes. That’s what a new study finds.1
The study included 12 healthy young men who regularly exercised but weren’t doing structured strength training programs. Each participant completed a lower-body resistance training workout, which included leg presses and knee extensions. Immediately after the workout, one leg was placed in cold water (8°C/46℉) and the other in warm/thermoneutral water (30°C/86℉) for 20 minutes. This allowed each person to act as their own control—helping the researchers directly compare cold vs. warm recovery in the same body and elucidate whether post-exercise CWI has systemic or localized effects.
After the water immersion, participants drank a special protein-rich shake with 20 grams of amino acids, 45 grams of carbohydrates, and a special tracer amino acid (L-[ring-13C6]-phenylalanine) that lets researchers track amino acid incorporation into skeletal muscle.
Over the next 4 hours, the researchers measured blood flow and microvascular perfusion (blood reaching tiny capillaries in muscle) in each leg using a special ultrasound technique, collected blood samples, and took muscle biopsies from each leg to measure how much of the tracer amino acid was actually incorporated into muscle proteins—a way to see how much “muscle-building” activity was happening.
Post-exercise cold “ices” gains
Immediately after CWI, the microvascular blood volume in the cooled leg was 60% lower than in the thermoneutral leg. This decrease in blood volume was not short-lived—it remained notably lower for up to three hours following exercise. Specifically, at 60 minutes post-immersion, blood volume in the cold-treated leg was 41% lower, and at 180 minutes, it was still 24% lower compared to the control leg.
In terms of microvascular blood flow, there was a roughly 68% reduction immediately after cooling, but this measure gradually returned toward the levels seen in the thermoneutral leg during the recovery period. Importantly, microvascular blood velocity itself was not affected by the cooling, indicating that the reduction in overall blood flow was driven by a decline in blood volume, rather than a change in the speed at which blood moved through the vessels.
Cooling also had a substantial impact on the larger blood vessels supplying the legs. Blood velocity in the femoral artery was lower in the cooled leg right after immersion and remained reduced at both 60 and 180 minutes into recovery. Likewise, blood flow through the femoral artery was reduced by about 50% immediately after immersion and remained suppressed at the 60-minute mark. Interestingly, the diameter of the artery itself did not differ between the cooled and control legs, suggesting that changes in flow were again primarily due to velocity rather than vessel size (as was observed for microvascular perfusion).
Lastly, amino acid incorporation into muscle was significantly reduced after cold immersion. The cold-treated leg had about 30% lower incorporation levels than the control leg, suggesting that cold water immersion impaired the muscle’s ability to use amino acids for repair and growth following exercise. Moreover, this reduction in amino acid incorporation was strongly linked to the observed reductions in microvascular blood volume, reinforcing the idea that decreased muscle blood supply can directly hinder the recovery process.
Without belaboring the point, it seems (once again) that all evidence indicates you should avoid getting into cold water after your workout. The long-term studies reveal a strength- and hypertrophy-mitigating effect and direct evidence—including the current study—lends mechanistic support.
Despite this, you’ll still see people on social media claiming that it’s still probably “no big deal” to use cold water immersion after your workout or that the “effects aren’t that big.” I don’t disagree. None of the evidence suggests that your gains are completely ruined if you take an ice bath after a workout; they’re just somewhat lower than they otherwise would be.
I think that this study gives us even more reasons to avoid cold water immersion after exercise. Microvascular blood flow (perfusion) and amino acids are crucial not just for building muscle—they’re essential for nearly all adaptive processes.
That means building bigger stronger muscle fibers but also signaling the creation of mitochondrial proteins and aerobic enzymes required for endurance training adaptations. If we halt nutrient delivery to muscles, we halt all adaptation. Given that post-exercise blood flow is also essential for recovery, there appears to be no good reason to use the cold after a workout. You’re getting less blood flow, making your post-exercise nutrition less effective, and dampening the body’s adaptive response.
For fear of contributing too much to the fear-mongering, I’ll end with a more reasonable conclusion. If you’re someone who enjoys doing a cold plunge and the only time that it works for you is in close proximity to the end of your workout, then go ahead and do it. Do I think it’s optimal? Probably not. But will it override hard training and long-term consistency? Certainly not.
However, if you are someone (like me) who really dreads the cold and instead embraces the heat (sauna or hot bath) after a workout, this is a perfect time to use science as an excuse to stay warm.
Thanks for reading. See you next Friday.
~Brady~
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I would like to see CWI studies done with CWI before strength training. Many people have always or shifted to using CWI as pre workout routine.
Brb shorting cold plunge stocks