Ice baths are very popular in the health and fitness space; however, new research suggests that they may be detrimental for muscle growth.
Introduction
Ice baths are all the rage in the health and fitness space. The modern fascination with ice baths can likely be traced to ‘The Iceman’, Wim Hof, and his controversial Wim Hof Method—a wellness protocol consisting of breath work, cold therapy, and commitment. Indeed, various popular podcast hosts have championed Wim Hof and his method, as well as the ostensible health and performance benefits of ice baths.
With that said, the performance effects of cold-water immersion (e.g., ice baths) are not well understood (neither are the health effects, but that’s a topic for another time). This brings us to a new study published just 10 days ago (February 2024) in the European Journal of Sport Science, which investigated the effect of post-workout cold-water immersion on muscle gains (1).
Wim Hof in ice. Image source: Science-Based Medicine.
Study Design
Methods
This new study was a systematic review and meta-analysis of eight randomised controlled trials. In a meta-analysis, researchers combine the results of a number of similar studies together into one result. This allows researchers to better understand whether an intervention has an effect on the outcome(s) of interest. In this example, researchers included eight studies that randomly assigned participants to either:
Perform a typical recovery method post-workout (e.g., active or passive recovery, static stretching, etc.), or
Immerse themselves in cold water straight after training
The researchers then analysed the results of all eight studies as one, to see if cold-water immersion performed straight after resistance training affects muscle growth.
Included Studies
All eight randomised controlled trials ranged from four to 12 weeks in length and administered training sessions at a frequency of two to three times per week. Three studies focused on lower body training, two focused on full-body training, two focused on handgrip training, and one focused on wrist flexor training. In all studies, cold-water immersion was performed within 15 minutes of completing resistance training and lasted 10–20 minutes at a temperature of 10–15 degrees Celsius. In three studies, the whole body was exposed to cold-water immersion, whereas three studies exposed only upper limbs, and two studies exposed only lower limbs. Muscle growth was assessed using a range of measures (e.g., DXA, MRI, muscle circumference).
Results
There was strong evidence for muscle growth in those who performed resistance training without cold-water immersion, whereas there was some evidence that those who engaged in cold-water immersion post-workout gained muscle, but these gains were likely small to negligible. In the main analysis, where both groups were compared, the resistance training group that didn’t perform cold-water immersion showed greater muscle gains relative to the resistance training group that did (Figure 1).
Figure 1. Forest plot comparing the effect of resistance training plus typical recovery methods (RT) with resistance training plus cold-water immersion (CWI + RT) on muscle gains (1). As you can see, the standardised mean difference of the average effect (at the bottom) favoured resistance training plus typical recovery methods. This means that resistance training plus cold-water immersion seems to lessen muscle growth relative to resistance training plus typical recovery methods.
The Findings in Context
This meta-analysis suggests that if your goal is to gain muscle, hopping into the ice bath after your workout is counterproductive. In fact, a separate (and recent) meta-analysis of 10 studies reported that post-workout cold-water immersion also decreases muscular strength (2)! While this may seem counterintuitive, it makes sense paired with an understanding of the physiological processes that drive muscle recovery.
Resistance training challenges (and tears) our muscles. In order to build back stronger, our muscles go through a short-term inflammatory response after training, while a process called muscle protein synthesis is simultaneously promoted (1). These short-term responses to training set off a cascade of physiological processes that combine to help us recover fast, and with newfound muscle gains and strength.
When we jump into the ice bath, we shut down these processes (to an extent). Therefore, we don’t recover as well as we would like, and hence, we don’t optimise muscle size or strength gains. In other words, cold-water immersion blunts the stress response that training provides, which is a necessary response in order to gain muscle size or strength.
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Summary
If you enjoy cold showers or ice baths, by all means carry on. But based on the current literature, I would recommend that you avoid doing them straight after a workout (and potentially limit their use throughout the week) if your goal is to gain muscle and/or strength.
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As always, thanks for reading!
Patrick Elliott, BSc, MPH
Health and Nutrition Science Communication Officer at Training121
Instagram: @just.health.info
Twitter/X: @PatrickElliott0
References
(1) Piñero A, Burke R, Augustin F, Mohan AE, DeJesus K, Sapuppo M, Weisenthal M, Coleman M, Androulakis-Korakakis P, Grgic J, Swinton PA, Schoenfeld BJ. Throwing cold water on muscle growth: A systematic review with meta-analysis of the effects of postexercise cold water immersion on resistance training-induced hypertrophy. Eur J Sport Sci. 2024;1–13. Available at: https://onlinelibrary.wiley.com/doi/10.1002/ejsc.12074
(2) Grgic J. Effects of post-exercise cold-water immersion on resistance training-induced gains in muscular strength: a meta-analysis. Eur J Sport Sci. 2023;23(3):372–80. Available from: https://onlinelibrary.wiley.com/doi/10.1080/17461391.2022.2033851
Technical Terms
Meta-analysis: This type of study combines the results of a number of studies that investigate a similar research question, to produce an overall estimate of the effect or association. For example, a meta-analysis of five studies investigating the effect of smoking on lung cancer would combine the results from all five studies into one overall result, with the intention of providing a better estimate of the true effect of smoking on lung cancer.
Randomised controlled trial: Also known as an RCT, this is a type of interventional study that randomly assigns a group of recruited individuals to distinct groups within a study. There are usually two groups: an intervention group, and a control (or comparison) group, but there can be many groups (e.g., multiple intervention groups). In this case, this is called a parallel RCT, as each individual only experiences one treatment (i.e., they’re either in the intervention group or the control group; parallel to the other group). In crossover RCTs, individuals experience both the intervention and control treatment, and differences in treatment effects between both conditions are measured (e.g., individuals eat Diet A for four weeks, then Diet B for four weeks, and the difference in effect(s) for an outcome (e.g., cholesterol) would be compared between both four-week periods). The rationale for randomising people to different groups is to reduce bias (i.e., to evenly distribute any factors that may influence (or bias) the outcome of interest among groups). For example, if we have a group of 1,000 people that will be given either a multivitamin or placebo pill to take every day for 10 years—to see if the multivitamin offers any protection for the risk of death compared to the placebo pill—we would randomise the 1,000 people to each group so that each group is similar for factors like age, physical activity status, smoking status, and so on. If we didn't do this, we might end up with one group being unbalanced with respect to any of these factors (e.g., older on average, containing more smokers or more physically inactive individuals, etc.). If this happened, the results of the study may be biased, as you would expect a group that has more smokers (for example) to be at greater risk of death than a group with less smokers—regardless of whether that group was assigned to take the multivitamin or placebo pill.
Muscle protein synthesis: The process by which our bodies build new muscle proteins (and hence, muscle tissue). This can be influenced by a range of factors, including nutrition, sleep, and exercise intensity.