This article provides practical insights into the research conducted by Prof Neil Walsh and Mike Zurawlew on heat acclimation through hot baths. While the original study presented the scientific aspects of the publication on this topic, it left readers with practical questions. Research findings are often limited to controlled conditions and may not easily translate to different situations, populations, or events. To address these concerns, the authors were interviewed to shed light on the practical aspects not typically found in research papers.
The Study: Heat Acclimation and Its Practical Implications
The study conducted by Neil Walsh and Mike Zurawlew involved challenging conditions with a temperature of 33°C. Although these conditions were extreme, the researchers found strong evidence that the intervention also reduces thermal strain in cooler conditions. They observed lower core body temperature, lower core temperature at sweating onset, and lower perceived exertion when participants exercised in temperate conditions of 18°C after the intervention. This suggests that even non-heat-acclimated endurance athletes performing in moderately warm conditions, such as Rio with temperatures likely ranging from 24-28°C, could benefit from taking a hot bath after exercise for six days. Heat acclimation achieved through this method may reduce thermal strain during exercise and potentially improve performance.
Heat Acclimation in Different Temperature Conditions
The study focused on a one-hour run, but the researchers believe that similar benefits could be seen in longer events, such as the Ironman distance in hot conditions like Hawaii. Although further studies are needed to confirm this, it is reasonable to expect that heat acclimation would lead to self-selection of a higher pace during endurance exercise in the heat. The researchers speculated that if they had used a longer running test, they might have observed an improvement in performance in temperate conditions after the intervention. However, the effect of heat acclimation on performance in temperate conditions remains a topic of debate.
Study Location and Participant Background
The study was conducted in North Wales, where average winter temperatures range from 3-9°C and summer temperatures range from 13-20°C. The season did not significantly impact the findings, as the number of participants in hot baths and control baths was balanced across seasons. Importantly, none of the participants were heat acclimated, and none had been exposed to hot conditions in the preceding three months.
Comparing Heat Acclimation Between Different Training Statuses
Regarding the participants' training status, the study included both recreationally active individuals and trained endurance athletes. While the primary aim of the study was not to compare heat acclimation between these groups, the data suggested that endurance-trained individuals might benefit less from the hot bath intervention due to their initial heat acclimation. However, it's worth noting that the hot bath exposure in this study was self-regulated, allowing participants to determine their duration in the bath.
Endurance-trained individuals, who completed longer durations in the hot bath on most days, actually experienced a greater stimulus for heat acclimation. Thus, they also demonstrated reductions in resting core temperature and exercising core temperature in the heat comparable to the recreationally active individuals. The endurance-trained participants even improved their 5k time trial performance in the heat by an average of 4%.
Beyond Performance: Additional Benefits of Hot Baths
The potential benefits of hot baths extend beyond running performance. Throughout history, hot baths have been associated with therapeutic effects on aching bones and muscles. Current research is exploring the cardiovascular, glucose regulation, and immune benefits of hot baths. Hot baths may offer advantages for injured athletes and individuals who struggle to engage in sufficient exercise, such as the elderly or those who are unwell.
Practical Advantages of Hot Baths for Heat Acclimation
In terms of the magnitude of heat acclimation achieved through hot baths, the researchers believe that their short-term method compares favorably with traditional heat acclimation practices. Unlike the need for environmental chambers and core temperature clamping in traditional methods, hot baths offer practical advantages. The absence of these requirements allows hot baths to be easily incorporated into post-exercise washing routines. The preliminary results from this study indicate a reduction in resting core temperature in almost all participants, which can be considered a "pre-cooling effect." Future studies should compare this new method with current practices to establish its efficacy.
Comparing Hot Baths with Saunas
Another question raised was whether saunas would have a similar or better effect. While one study discussed in the researchers' paper demonstrated the benefits of regular sauna bathing after exercise on exercise performance in the heat, practicality and thermoregulation measurements were not addressed.
Potential Risks and Guidelines for Hot Bath Approach
Regarding the potential risks associated with the hot bath approach, it is essential to follow the provided guidelines carefully. Just as individuals must heed cues to stop during exercise in the heat, the same attentiveness applies to hot baths. Highly motivated individuals may overlook these cues, increasing the risk of heat exhaustion, which can progress to heat stroke. Completing the full 40-minute hot bath on each of the six days is neither safe nor necessary for everyone. Gradual progression is recommended as the individual adapts to the heat. Additionally, individuals should take a few minutes to sit after getting out of the hot bath to allow blood pressure to return to normal and reduce the risk of feeling lightheaded.
Summary of Practical Guidelines and Findings
In summary, the study conducted by Neil Walsh and Mike Zurawlew provides practical guidelines for heat acclimation through hot baths. The findings suggest that the intervention can reduce thermal strain not only in extreme conditions but also in cooler temperatures. The benefits of hot baths extend to endurance athletes performing in various temperature conditions, including longer events in hot locations. The study included participants with different training statuses and demonstrated improvements in performance and reductions in core temperature across both groups.
Hot baths offer practical advantages over traditional methods and may have additional benefits beyond running performance. However, it is crucial to follow the guidelines and be aware of the associated risks. Further research is needed to explore the underlying mechanisms and compare hot baths with other heat acclimation approaches. By embracing the simple act of taking a hot bath, athletes and individuals can optimize their performance and enhance their well-being.
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Scientific reference
- Zurawlew, Walsh, Fortes, Potter. Post-exercise hot water immersion induces heat acclimation and improves endurance exercise performance in the heat. Scand J Med Sci Sports DOI: 10.1111/sms.12638
