In the world of fitness and performance, we’re always searching for new ways to maximise the benefits of training. Whether it’s for our own progress or that of our clients, we explore everything from supplementation to advanced training methodologies in the hope of gaining an extra edge. In addition to these well-known strategies, emerging approaches such as compression therapy, infrared sauna use, and electrical stimulation devices have also been proposed as potential aids for recovery and performance enhancement.
Strategies such as periodisation ensure that we cycle intensity and recovery to avoid overtraining and optimise progression. Nutritional interventions, from protein supplementation to creatine loading, have long been advocated for their role in muscle growth and recovery. Massage and foam rolling are commonly employed to reduce muscle soreness and enhance flexibility. Meanwhile, cross-training introduces variety to prevent plateaus and improve overall athletic performance. Each of these methods has its place, and many have been rigorously studied. However, one recovery tool that has often been overlooked or viewed with scepticism, is hot water immersion.
History of Bathing
The idea that heat can aid recovery is not new. Throughout history, different cultures have recognised the therapeutic benefits of heat. Ancient Greeks and Romans built elaborate bathhouses where soldiers and athletes would soak to relieve muscle fatigue and prepare for battle or competition. Traditional Chinese medicine has long incorporated heat therapy, believing it promotes circulation and balances the body’s energy. Japanese onsen culture has maintained the practice of hot bathing for centuries, associating it with both relaxation and health benefits. In modern times, scientific research has supported these notions, with studies indicating that heat therapy can improve blood flow, reduce muscle stiffness, and aid in the recovery process by decreasing inflammation and oxidative stress.
With such a strong historical and scientific foundation, the question remains: can hot bathing truly enhance training adaptations? Could simply sitting in a hot bath after training genuinely enhance exercise adaptations?
Research May Tell Us
A team of researchers set out to investigate this very question. Their study focused on whether a home-based bathing intervention (HBBI) could enhance muscle strength gains and protect cardiovascular function when combined with short-term resistance training (RT).
Thirty-one healthy young men were recruited for this study. While this sample provides valuable insights, it does present some limitations. The lack of diversity in participants means that the findings may not be fully generalisable to other populations, such as older adults, women, or individuals with different fitness levels. Additionally, the relatively small sample size could limit the statistical power of the results, making further research with larger and more varied groups necessary to confirm these findings.
They were randomly assigned to one of three groups. The first group served as a control and was instructed to shower only, without immersing themselves in a bath. The second group took daily baths at a thermoneutral temperature of 36°C, a temperature considered to be neither too hot nor too cold for affecting core temperature or vascular resistance. The third group was assigned to hot water baths at 40°C, a temperature more in line with traditional hot bathing practices.
Before the experiment began, participants’ baseline neuromuscular and cardiovascular function was assessed. The primary measure of strength was maximum voluntary contraction (MVC) of the knee extensors, which would indicate improvements in muscle strength. Additionally, researchers measured electrically evoked knee extension torque, a technique used to assess peripheral muscle condition. Cardiovascular markers, including mean arterial pressure (MAP) and arterial stiffness, were also recorded.
Participants then undertook a two-week resistance training programme, consisting of five sessions of three sets of 10 isometric knee extensions at 60% MVC. Each training session was supervised to ensure consistency. Throughout the intervention period, the groups followed their assigned bathing protocols, either showering, bathing at 36°C, or bathing at 40°C. At the end of the two weeks, all measurements were repeated to assess whether the bathing intervention had any effect on training adaptations.
What the Study Found
The results revealed some interesting findings. The 40°C hot bathing group experienced the greatest improvement in maximum voluntary contraction (MVC) of the knee extensor. The increase in muscle strength in this group was categorised as having a large effect size, indicating that hot bathing could be contributing positively to strength gains. The 36°C group also saw an improvement, though it was more moderate, while the shower-only control grouphad the smallest increase in muscle strength.
Interestingly, when looking at peripheral muscle condition, the results were quite different. The control group, which did not bathe, exhibited a notable increase in the 10/100 Hz ratio, suggesting an improvement in low-frequency muscle function. This metric is often used to assess neuromuscular fatigue and recovery. However, the bathing groups did not show this adaptation. This suggests that bathing, particularly hot bathing, might reduce resistance training-induced muscle stress, which in turn could limit neuromuscular adaptations.
The study also examined the effects of bathing on cardiovascular function. Measures of mean arterial pressure (MAP), heart rate (HR), and arterial stiffness (baPWV) did not significantly change in any of the groups. This suggests that short-term resistance training does not appear to negatively impact cardiovascular function, regardless of bathing habits.
One particularly intriguing finding was the subjective experience of the participants. The 40°C bathing group reported higher levels of comfort and better perceived recovery compared to the 36°C group. This suggests that while there may be physiological benefits, there is also a significant psychological component—hot baths simply feel better and may contribute to a greater sense of well-being post-exercise.
What This Means
These findings provide an interesting perspective on how hot bathing can influence resistance training adaptations. The fact that muscle strength increased the most in the hot bathing group suggests that post-training heat exposure could enhance neuromuscular recovery and performance gains. However, the fact that neuromuscular adaptations were more pronounced in the shower-only group raises questions about whether heat may actually limit some aspects of training-induced stress adaptations. This highlights the importance of context when recommending recovery strategies.
If the goal is to maximise strength gains while ensuring recovery, hot bathing at 40°C appears to be a viable strategy. It is a simple, accessible, and cost-effective recovery method that could be integrated into a client’s routine. However, if the goal is to increase neuromuscular adaptations and improve peripheral muscle function, it may be beneficial toavoid excessive heat exposure post-training.
The findings on cardiovascular health are reassuring, as they indicate that short-term resistance training does not negatively impact cardiovascular function. This aligns with previous research suggesting that moderate-intensity resistance training does not pose cardiovascular risks and may even have benefits for arterial function over time. However, other studies have shown that high-intensity resistance training can lead to temporary increases in arterial stiffness and blood pressure. The absence of significant cardiovascular changes in this study may be due to the relatively short duration and moderate intensity of the training programme. Further research is needed to determine whether longer-term interventions or higher training intensities would yield different outcomes. This means we can confidently encourage resistance training among clients without concerns about adverse cardiovascular effects, regardless of whether they include hot baths in their routine.
Practical Takeaways
If you’re looking to incorporate these findings, here are some actionable tips. Monitoring client responses to hot bathing is essential; consider tracking their strength progression, recovery times, and subjective feedback over several weeks to determine whether it is a beneficial strategy for them. Adjust recommendations based on their performance, comfort levels, and training goals.
- Encourage clients to experiment with hot baths after training to see if they find it beneficial for muscle recovery and general comfort.
- If strength development is the primary goal, consider suggesting regular post-training hot baths at 40°C for around 10 minutes.
- For clients looking to enhance neuromuscular adaptations, alternative recovery methods, such as active recovery or cold water immersion, might be preferable.
- Reassure clients that resistance training does not negatively impact cardiovascular health in the short term, regardless of their recovery strategy.
- Pay attention to individual responses, as recovery methods can be highly personal. What works for one client may not work for another.
While more research is needed to explore the long-term effects of hot bathing on strength and muscle function, this study provides compelling evidence that it can play a role in post-training recovery. Whether used as a tool for enhancing performance gains, promoting relaxation, or simply feeling good after a tough session, hot baths could be a valuable addition to a well-rounded training programme.
Reference
Takeda, R., Amaike, T., Nishikawa, T., & Watanabe, K. (2025). Effect of home-based hot bathing on exercise-induced adaptations associated with short-term resistance exercise training in young men. Physiological Reports, 13, e70188. Click here to review the full research article.
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Recovery is a crucial aspect of any fitness programme, and as a personal trainer, understanding how to optimise it can make all the difference for your clients. At TRAINFITNESS, our Nutrition & Exercise Specialist & Master Diplomas™, Women’s Health & Exercise Specialist & Master Diplomas™, and Strength & Conditioning Exercise Specialist & Master Diplomas™ go beyond just training methods, we teach you how to integrate effective recovery strategies into your programmes. A recent study found that hot water immersion at 40°C led to a significant increase in muscle strength, with a large effect size (η² = 0.450) compared to showering alone. However, it also revealed that recovery techniques influence neuromuscular adaptations differently, highlighting the importance of selecting the right approach for individual goals. Whether you’re designing nutrition plans, working with female clients, or coaching athletes in strength and conditioning, understanding recovery, from hot baths to active recovery and beyond, is key to maximising results and preventing burnout. When you qualify with us, you’ll learn how to apply the latest research to help your clients perform at their best.
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