"Cold Water Immersion & Muscle: The Science-Backed Truth on Recovery Benefits"

Wellness and Recovery? What the Science Says

(Source: The Washington Post, by Gretchen Reynolds)

Cold Water Immersion & Muscle

Introduction: The Icy Trend and Its Scientific Scrutiny

In recent years, ice baths and cold plunges—terms often used interchangeably to describe soaking in near-freezing water—have surged in popularity. Fueled by endorsements from podcasters, social media influencers, and professional athletes, these frigid dips are widely touted for their purported benefits in exercise recovery, muscle growth, and overall personal wellness, including mood elevation and mental resilience. However, despite their widespread adoption and anecdotal acclaim, a critical question remains: do they actually work as claimed, particularly for physical recovery? A new study, adding to a growing body of evidence, suggests a nuanced and potentially contradictory answer, particularly concerning muscle recovery and growth after resistance training.

New Research Challenges Recovery Claims

The core of the latest study, led by Milan Betz, a doctoral student at Maastricht University in the Netherlands, directly investigated the relationship between frigid water immersion and resistance training. The findings present a significant challenge to the popular belief that cold plunges accelerate physical recovery post-workout. According to the study's authors, plunging limbs into icy water after weightlifting appears to slow blood flow to muscles, which in turn hampers their ability to recover and grow. This suggests that instead of amplifying workout benefits, cold plunges might actually diminish them. "It looks like it’s not a great idea" to soak in freezing water after lifting weights, Betz stated, succinctly summarizing their conclusion.

These findings are not isolated; they contribute to mounting evidence from prior research that also casts doubt on the efficacy of ice baths for muscle hypertrophy (growth).

Prior Evidence Undercutting Muscle Growth

· The 2015 Australian Experiment: A notable experiment conducted in Australia in 2015 involved 21 men who engaged in twice-weekly weightlifting sessions. Half of these men consistently cold-plunged after each session, while the other half did not. After three months, the results were striking: the muscles of the cold-plunging group were nearly 20 percent smaller and weaker than those of the non-cold-plunging group, despite both groups following identical exercise routines.

· The 2024" Review—"Throwing Cold Water on Muscle Growth": A comprehensive review of existing research published in 2024, provocatively titled "Throwing Cold Water on Muscle Growth," concluded that the best available evidence indicates cold plunges after resistance training can "attenuate hypertrophic changes." In simpler terms, this means that your muscles will not grow as much as they otherwise would if you consistently use cold immersion post-workout.

Cold Water Immersion & Muscle

The Mechanism: Impaired Blood Flow and Protein Uptake

The consistent theme emerging from these studies points to a specific physiological mechanism: cold water impedes optimal blood flow to muscles.  The authors of the 2024 review speculated that frigid temperatures cause blood vessels to constrict, thereby limiting the delivery of vital nutrients, especially protein, to muscles. Muscles heavily rely on these nutrients to repair and rebuild themselves after the strenuous demands of exercise. Less blood flow translates to a reduced supply of protein, which in turn leads to a weaker recovery response.

Until recently, this process had not been directly observed in action. Betz and his colleagues sought to provide this missing piece of evidence. They recruited 12 healthy young men and, using portable ultrasound machines, meticulously tracked baseline blood flow in their legs. After a challenging leg workout (leg press and leg extension exercises), volunteers underwent a controlled cold plunge: one leg was immersed in icy 30-degree Fahrenheit water, while the other was placed in tepid 80-degree water for 20 minutes.

Following this, participants consumed a recovery shake containing protein molecules tagged with a biochemical tracer, allowing researchers to track protein absorption. Throughout the subsequent hours, blood flow was continuously monitored via ultrasound.

Cold Water Immersion & Muscle

Direct Evidence: Reduced Blood Flow and Protein Absorption

The results of Betz's study provided critical confirmatory evidence:

· Substantial Blood Flow Reduction: Blood flow dropped significantly in the cold-plunged leg compared to the unchilled limb and remained suppressed for several hours.

· Reduced Protein Absorption: Consequently, the muscles in the chilled leg received and absorbed far less protein from the recovery shake.

· Blunted Gains: Over time, this diminished protein intake would predictably result in blunted gains in both strength and muscle mass from the weight training.

Brad Schoenfeld, an exercise scientist at Lehman College in New York and co-author of the 2024 review, affirmed that these results "provide confirmatory evidence" that cold plunges can indeed negatively alter the desired effects of weight training by reducing blood flow and protein uptake.

Remaining Questions and Nuances

While the findings are compelling, the researchers acknowledge that this was a single, small study, leaving several questions unanswered:

· Other Exercise Modalities: Would similar effects be observed for recovery from other forms of exercise, such as running, cycling, or team sports? Betz believes the impacts would likely be similar, but emphasizes the need for specific studies.

· Demographic Differences: The study focused on young men. How might cold plunges affect women and older populations? Betz anticipates similar outcomes but stresses the importance of dedicated research.

· Timing and Protocol Variables: Denis Blondin, a professor of health sciences at the University of Sherbrooke who studies metabolism and cold exposure (and was not involved in the new study), raises questions about the importance of timing. Could ice baths several hours after a workout yield different results? Do details like duration of immersion, amount of body submerged, and exact water temperature alter the effects? More large-scale research is needed to understand these nuances.

The Mental Aspect: Still Valid?

It's crucial to differentiate the physiological effects on muscle recovery from the widely reported psychological benefits of cold plunges. Many individuals engage in cold immersion for reasons unrelated to exercise recovery, such as building mental fortitude, resilience, or simply experiencing a mood lift and stress relief. The new study did not examine these psychological outcomes.

As Betz noted, if you find psychological comfort or mental strength in cold plunges, "there’s no reason to change your mind" about that benefit. However, for those whose primary goal is to maximize strength and muscle mass gains from weight training, the cumulative evidence, including this latest study, strongly suggests that skipping an ice bath immediately after a workout is likely the best course of action.