For decades, elite runners have traveled the world to train at high altitudes, where the thin air prompts the body to produce more red blood cells, enhancing endurance performance upon returning to sea level. However, this method comes with significant costs, including time away, financial investment, and long-haul travel, making it inaccessible for many athletes, such as those participating in this year’s London Marathon.
Seeking a more accessible alternative, researchers have turned their attention to heat exposure. Traditionally used by athletes to acclimate to hot climates, the study explored whether prolonged heat exposure, over four to five weeks, could induce physiological changes akin to those achieved through altitude training.
Exploring Heat as an Alternative
In a groundbreaking study, a group of well-trained endurance runners was recruited to maintain their regular training regimen with one addition: five hot baths per week for five weeks. These baths, conducted in standard home bathtubs, maintained a water temperature of 40°C for 45 minutes per session, completed shortly after training.
Before and after the intervention, researchers measured several endurance physiology markers, including red blood cell volume, heart structure, and maximal oxygen uptake (VO₂max), widely regarded as the gold standard for aerobic fitness.
Key Findings
The results were compelling. After five weeks, the runners displayed a significant increase in red blood cell volume, indicating more oxygen-carrying cells in their bloodstream. This was unexpected since altitude training increases red blood cell production due to reduced oxygen availability, whereas heat does not limit oxygen. Instead, heat expands the plasma, diluting red blood cells and prompting the body to produce more to restore balance.
On average, the runners’ VO₂max increased by around 4%, allowing them to reach higher speeds during maximal treadmill tests.
Additionally, changes in heart structure were observed. Endurance training typically enlarges the heart’s left ventricle, and the heat intervention further increased its volume, likely due to the additional blood created through heat exposure.
Implications for Marathon Training
For runners and coaches, these findings are intriguing. Heat exposure could offer a low-impact method to induce beneficial changes without the added strain of more exercise, which always carries injury risks. In contrast, hot baths stress the cardiovascular system without additional strain on muscles and joints.
Moreover, this approach is relatively accessible. Most people have access to a bath, making it a cost-effective alternative to altitude camps. This opens the door to more equitable access to performance-enhancing, yet entirely legal, training strategies.
Considerations and Future Research
As with all research, there are limitations. The study followed a specific protocol: 40°C water, 45 minutes per session, five times per week, for five weeks. It remains unclear whether shorter sessions, lower temperatures, or other heat sources, such as steam rooms or saunas, would yield similar results.
Safety considerations are also paramount. Prolonged heat exposure can increase the risk of dehydration, dizziness, and heat illness. Adequate hydration, avoiding overheating, and appropriate supervision are crucial. Individuals with underlying health conditions should seek medical advice before attempting this protocol.
Finally, while physiological markers and treadmill performance improved, actual marathon race times were not measured. Although VO₂max improvements are strongly linked to endurance performance, future studies must confirm how these changes translate to real-world competition.
Looking Ahead
Despite these considerations, the study suggests that performance gains do not always require more miles or international travel. Sometimes, adaptation can be stimulated in surprisingly simple ways. For marathon runners seeking a practical way to enhance their training, passive heat exposure might be a straightforward tool worth exploring.
/Courtesy of The Conversation. This material from the originating organization/author(s) might be of the point-in-time nature, and edited for clarity, style, and length. Mirage.News does not take institutional positions or sides, and all views, positions, and conclusions expressed herein are solely those of the author(s).
