It seems like everyone and their mother is talking about the benefits of ice baths, while hot baths don’t get much attention. However, a new study investigated how ice baths and hot baths influence muscle recovery, and the results are quite interesting.
Introduction
Ice baths have been popular in high-performance settings for some time. As a kid, I remember using the pool in Carton House when the Irish rugby team were training there, and seeing them hop in and out of massive ice baths beside the pool. At the time, this was deemed as cutting edge stuff only reserved for top athletes. But that is no longer the case.
In 2024, it seems that if you’re not using ice baths you’re in the minority. Okay, while that’s an exaggeration, it is fair to say that a lot of regular people are using ice baths or cold plunges quite often. The reasons for this often relate to performance goals: people want to recover faster and perform better in their chosen sport or exercise type. However, as we have written before, ice baths seem to be detrimental to muscle and strength gains, so it doesn’t seem to be the best option for improving performance in the gym at least.
A new study has attempted to directly measure if ice baths can affect markers of muscle recovery, but with an interesting wrinkle not investigated in many other studies (1). In addition to looking at the effect of ice baths, researchers also investigated whether hot baths would influence recovery. For some reason, hot baths don’t get the acclaim of ice baths, so it is welcome to see these researchers measure the effect of hot and cold water immersion on markers of muscle recovery.
Thumbnail from our article: Cooling the Hype on Post-Workout Ice Baths.
The Study
Thirty young and physically active males (training >6 hours per week) took part in this 3-day study. On the 1st day, participants’ rate of force development in their quadriceps, as well as their maximal force development (known as peak torque), were measured using a machine known as an isokinetic dynamometer. This was done so that researchers could establish a baseline measure of each participant's explosive and maximal muscle strength, respectively. Then, participants completed an exercise routine designed to induce muscle damage within their quadriceps muscle. This involved performing 7 sets of 10 repetitions of maximal eccentric contractions on the isokinetic dynamometer, followed by 1 set of 3 repetitions of maximal concentric contractions to re-measure rate of force development and maximal force development (or peak torque) after the eccentric repetitions. Exercise-induced muscle damage was defined as a reduction in peak torque of 15–25% in these concentric contractions.
Within 30 minutes of completing the exercise activity, each participant bathed waist down in either hot (41°C), warm (36°C), or cold (11°C) water. The researchers ensured that an equal number of participants were assigned to each of these conditions (i.e., 10 in each condition). While the hot and cold water conditions were the ones of interest to the researchers, they included a warm water condition to act as a control because previous research has indicated that warm water baths (i.e., 36–40°C) do not reliably impact neuromuscular recovery.
For the hot water condition, participants’ core body temperature was increased to 38.5–39°C and then maintained there for 25 minutes. This was based on previous work showing this protocol improved neuromuscular recovery. For the warm water condition, participants bathed for a similar length of time as those in the hot water condition. For the cold water condition, participants bathed for 11 minutes. This was based on recommendations to improve neuromuscular recovery and decrease muscle soreness.
On the 2nd and 3rd days, participants’ rate of force development in their quadriceps, as well as their maximal force development, were once again measured using an isokinetic dynamometer to see how their explosive and maximal strength recovered over the following 24 and 48 hours.
An athlete using an isokinetic dynamometer. Image source: Movement F1rst.
Results
The main measure the researchers were interested in was rate of force development; a measure of explosive strength. Results showed that only the hot bath condition was able to mitigate the decline in rate of force development experienced after the exercise-induced muscle damage at 48 hours post-exercise. Effectively, this means that the hot water bath facilitated neuromuscular recovery for explosive strength, whereas the cold and warm bath conditions didn’t seem to.
When it comes to maximal force, measured as peak torque, the cold water bath was able to somewhat mitigate the decline in maximal force production experienced after the exercise-induced muscle damage at 24 and 48 hours post-exercise-induced muscle damage, whereas the hot water bath did so only at 48 hours post-exercise-induced muscle damage. The warm water bath condition did not mitigate this decline in maximal force production at 24 or 48 hours post-exercise-induced muscle damage.
Key Takeaway
The results of this study suggest that for athletes who engage in explosive force-generating activities like sprinting and jumping, a hot water bath may be a better option than a cold water bath for enhancing neuromuscular recovery.
Nerdy point: This study wanted to compare how different water temperatures (hot, warm, and cold baths) affect muscle recovery. But instead of comparing how the baths work against each other, they only looked at changes within each group (like how muscle recovery changed after hot baths or cold baths separately). To really see which temperature is most effective, they should have compared the overall changes between the groups (for example, how much recovery improved in the hot bath group compared to the warm or cold bath groups).
Summary
This study is another that suggests that cold water immersion is likely ineffective and suboptimal for improving neuromuscular recovery and subsequent exercise performance. While hot water immersion showed an ability to mitigate declines in rate of force development experienced after exercise-induced muscle damage, it may not be very practical for athletes, as the protocol lasted between 40–60 minutes (because it took an average of 22 minutes for participants’ core body temperature to reach the required range, which they then maintained for 25 minutes).
So, does this mean that ice baths are a ‘waste of time’, as Roy Keane said in a recent video from The Overlap. I'd be inclined to agree, especially considering their detrimental effect on muscle growth and strength. However, as I have said before, if you feel a benefit from them and enjoy doing them, go for it. But this study suggests that if anything, you would be better off spending time in a hot bath after training to enhance muscle recovery.
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As always, thanks so much for reading!
Patrick Elliott, BSc, MPH
Health and Nutrition Science Communication Officer at Training121
Email: [email protected]
Instagram: @just.health.info
Twitter/X: @PatrickElliott0
References
(1) Sautillet B, Bourdillon N, Millet GP, Billaut F, Hassar A, Moufti H, Ahmaïdi S, Costalat G. Hot But Not Cold Water Immersion Mitigates the Decline in Rate of Force Development following Exercise-Induced Muscle Damage. Med Sci Sports Exerc. 2024. Available at: https://journals.lww.com/acsm-msse/abstract/9900/hot_but_not_cold_water_immersion_mitigates_the.571.aspx
Technical Terms
Isokinetic dynamometer: This is a specialised machine used to measure the strength and power of your muscles while they move a joint, like your knee or elbow, at a constant speed. It ensures that no matter how hard you push or pull, the machine controls how fast you move, which allows for precise measurement of how much force your muscles can produce.
Eccentric contraction: This is a muscle contraction where the muscle lengthens (e.g., lowering a weight).
Concentric contraction: This is a muscle contraction where the muscle shortens (e.g., picking up a weight).
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