New research shows ice baths might be undermining your muscle gains
In recent years, cold-water immersion has graduated from niche recovery ritual to global wellness trend. Scroll through social media or tune into your favorite health podcast and you’ll find athletes, influencers, and entrepreneurs plunging into ice baths in pursuit of faster recovery, reduced soreness, and even mental clarity. Entire startups now sell sleek at-home tubs, while celebrity backers hype up the benefits. But a growing body of science is putting on the brakes. A new study published in Medicine & Science in Sports & Exercise by researchers at Maastricht University suggests that post-exercise cooling may come with an unintended cost: reduced muscle adaptation. In other words, the same icy plunge that helps you feel better may also be quietly slowing your gains.
Using a clever within-subject design, the researchers had 12 recreationally active young men perform a standard resistance workout, then plunge one leg into cold water (8°C) and the other into thermoneutral water (30°C) for 20 minutes. Both legs were then monitored over four hours for changes in blood flow and nutrient absorption. The cold leg, it turns out, didn’t just get numb. It got less blood. And that meant fewer amino acids delivered to the muscle, resulting in lower rates of muscle protein synthesis. The bottom line: cooling may soothe the pain, but it also might short-circuit the gain.
What Happens Under the Surface
Blood flow isn’t just a courier for oxygen and nutrients—it’s a critical signal that tells your body where to send resources for repair. After a hard workout, the increased blood flow to exercised muscles helps kick off recovery by flooding the area with amino acids, growth factors, and other tools of the trade. But when the cold leg in this study was immersed in 8°C water, its microvascular blood volume plummeted compared to the thermoneutral control. At multiple points during recovery, the cold leg maintained significantly lower perfusion.
Notably, this wasn’t just a reduction in major artery flow—which can still send blood past muscles without actually nourishing them. It was a drop in microvascular perfusion, measured via contrast-enhanced ultrasound, capturing the capillary-level dynamics that matter for nutrient delivery. By the four-hour mark, the researchers took muscle biopsies and found something striking: incorporation of amino acid tracers into muscle protein was about 30% lower in the cooled leg. The correlation was strong. Less blood flow, less muscle-building.
The Recovery Beverage Test
To test whether these changes in blood flow translated into real metabolic consequences, the researchers provided participants with a recovery drink immediately after immersion: 45 grams of carbohydrate and 20 grams of amino acids, including a tracer (L-[ring-13C6]-phenylalanine) that would allow precise tracking of protein synthesis. This design captured not just whether amino acids reached the bloodstream (they did), but whether they actually got into muscle and became part of new muscle proteins (they didn’t, or at least not as much in the cold leg). Despite equal amino acid availability in circulation, tracer incorporation into muscle was meaningfully lower in the cold leg, suggesting that impaired perfusion, not digestion or absorption, was the choke point.
Why does this matter? Because it underlines the difference between what you ingest and what your muscles actually use. In endurance and strength training alike, nutrient timing and delivery are essential. But if the muscle isn’t perfused, even the best recovery shake becomes a detour with no destination.
Challenging a Popular Recovery Habit
The use of ice baths and cold-water immersion dates back decades, fueled by tradition, anecdote, and the intuitive appeal of "feeling better faster." In recent years, it's exploded in popularity—boosted by wellness influencers, podcast hosts, and recovery-focused startups sponsoring everything from at-home tubs to infrared saunas. Cold has become cool. There’s some truth behind the trend: cold exposure can reduce pain perception, ease muscle soreness, and offer short-term relief. But recent evidence, including the current study, raises a red flag about the long-term cost. Previous studies have already suggested that cold exposure post-exercise may impair anabolic signaling and muscle growth. This new study goes a step further, offering a plausible mechanistic explanation: by reducing blood flow, cold blunts the muscle’s access to the very ingredients it needs to recover and adapt. The findings hold particular relevance for resistance training, where hypertrophy and strength gains are driven by repeated stress and repair cycles. If cooling interferes with that adaptation loop, the trade-off might not be worth it.
The Limits and the Real-World Takeaways
Of course, this was a controlled lab study with young, recreationally active men. We can’t assume the same effects apply equally to elite athletes, women, older adults, or individuals with more fat insulation (which may buffer the cooling effect). Nor does this study weigh the potential benefits of cooling for other outcomes, like perceived soreness, mood, or sleep. Still, the implications are real enough for strength-focused athletes. If your goal is to build muscle, recover stronger, and adapt optimally, ice baths may not be your friend—at least not immediately post-workout. Waiting several hours after training before cooling, or reserving ice baths for competition or injury scenarios, may be a better strategy. As with many performance tools, timing matters.
For endurance athletes, the picture may be more nuanced. While muscle protein synthesis is still essential—supporting not just muscle repair but also mitochondrial adaptation—it’s possible that the anti-inflammatory and soreness-reducing effects of cold-water immersion provide short-term value after grueling long runs or multi-day efforts. Whether these benefits come at a cost to longer-term aerobic adaptations remains unclear. That’s an open question and a valuable area for future research.
Warming Up to a New Idea
This study also opens the door to a fascinating question: could the opposite of cooling—warming—actually enhance post-exercise perfusion and nutrient uptake? Some previous data suggest hot-water immersion doesn’t impair protein synthesis in the way cold does, though it’s unclear whether it offers a true advantage. Still, in populations with impaired circulation or reduced muscle responsiveness (like older adults), boosting blood flow after exercise could be a promising area of study.
Meanwhile, the message is this: muscle recovery is a complex, finely tuned process. It relies not just on what you eat or how hard you train, but on whether your body can deliver the raw materials to the right place at the right time. Cooling may offer a shortcut to feeling better, but in the long run, it might just be cutting off the path to getting better. That doesn’t mean ice baths have no role—used strategically, especially for managing soreness, inflammation, or multi-day recovery demands, they remain a useful tool. Just don’t expect them to do the job of adaptation. When it comes to building muscle—or endurance—sometimes the best recovery strategy is to stay warm, stay patient, and let your blood do its job.