For endurance athletes, preparing for the heat is not simply a matter of drinking more. The environment you train in, the heat stress you experience and the time available before race day all matter. New research suggests that adaptations from training in dry heat can transfer to humid conditions—but it does not mean every athlete can follow the same recipe.
What the research found
A study published online on 12 October 2026 in Medicine & Science in Sports & Exercise examined trained male cyclists who completed heat-acclimation sessions in either hot, dry conditions or warm, humid conditions. After eight days of acclimation, the cyclists completed 30-minute time trials in both environments.
Both approaches improved performance in the environment in which the athletes acclimated and in the other environment. In the humid-condition time trial, performance improved by a similar amount following either dry-heat or humid-heat acclimation. In dry conditions, the dry-heat protocol produced a larger improvement than the humid-heat protocol.
The researchers also observed changes in sweating and other physiological responses consistent with heat adaptation. Their conclusion was that the overall heat stimulus may be more important than matching every detail of the acclimation environment to the eventual race.
That is a useful finding, but it needs context. The study involved a small group of trained male cyclists and a controlled protocol. It does not establish an ideal plan for women, less-trained athletes, runners, ultra-distance competitors or every real-world race environment.
Why this matters in South Africa
South African endurance athletes can encounter very different conditions across a season. An athlete may train inland in dry heat and then race on a humid coast. Trail and road events can also expose athletes to changing temperatures, sun, wind, altitude and limited opportunities to cool down.
Heat acclimation is the process of repeatedly exercising in the heat so the body can adapt to the thermal stress. Depending on the protocol and athlete, adaptations may include changes in sweating, cardiovascular strain and the ability to sustain work in hot conditions. These adaptations take time; they are not something to improvise during race week.
The new study offers a reassuring possibility: a well-designed heat-acclimation block in one type of heat may help in another. But the goal should not be to reproduce a laboratory protocol blindly. It should be to prepare safely for the conditions the athlete is likely to face.
What should athletes do?
1. Start with the race environment. Look at expected temperature, humidity, start time, course exposure, elevation and opportunities for cooling. A hot, dry inland race and a warm, humid coastal race can place different demands on the athlete even when the thermometer tells only part of the story.
2. Build heat exposure into the plan gradually. Heat sessions add stress to training. They should be introduced with attention to the athlete’s current training load, recovery, health and experience. More heat is not automatically better, and heat sessions should not compromise the key training work that matters most.
3. Do not confuse acclimation with hydration. Acclimation, fluid strategy, sodium intake, cooling, pacing and carbohydrate availability are related but distinct parts of preparation. An athlete can be acclimated and still make poor decisions about fluid intake or pacing. Equally, drinking more does not replace heat preparation.
4. Practise race-day decisions. Use training to rehearse pacing restraint, cooling options and a fluid/fuelling plan appropriate to the athlete and event. Individual sweat losses, gastrointestinal tolerance, race duration and aid-station access matter. Avoid adopting a universal fluid or sodium target based on a headline.
5. Protect recovery. Heat can increase the overall load of a session. Coaches should consider how the athlete responds and adjust intensity or duration when needed, rather than stacking heat stress on top of an already demanding training week.
The MCC coaching perspective
The practical message is not that dry-heat training is always superior or that eight days is the right answer for everyone. It is that heat preparation can be planned as a training block, and the actual environmental demands of the goal event should inform that plan.
For an athlete preparing for a hot race, an MCC coach can help align heat exposure with the training calendar, monitor how the athlete responds, and coordinate it with pacing, cooling, fuelling and hydration. The plan should be individualised rather than copied from a single study.
Bottom line: Training in dry heat may provide useful adaptations for racing in humid heat, but the evidence is still developing. Prepare for the environment, manage the extra training stress and avoid treating acclimation as a substitute for sound pacing, cooling and fuelling.
This article is educational and does not replace individual medical advice. Athletes with relevant health concerns or a history of heat illness should seek appropriate professional guidance before undertaking deliberate heat training.
Source:
Research: CrossAcclimation and Endurance Performance Following Adaptation to Dry and Humid Heat (McDonald et al., 2026), Medicine & Science in Sports & Exercise. https://doi.org/10.1249/MSS.0000000000004190
Related study: Dry and humid heat acclimation induces similar adaptations and cross-acclimation benefits in trained male cyclists. Journal of Physiology, 2026. https://doi.org/10.1113/JP290089