Various, literally “hot” major sporting events occupy athletes, coaches, scientists, spectators, media and many more. For example, the World Athletics Championships in Doha are in full swing, the Ironman showdown in Hawaii is just around the corner and the Olympic Games next summer will be another event in a row. What these competitions have in common is the climatic condition of the heat, which face participants with special and sometimes new challenges.
Exercising under heat conditions induces thermoregulatory and other physiological strain that can lead to impairments in endurance exercise capacity. During physical activity in the heat, skin blood flow and sweat rate increase to allow for heat dissipation to the surrounding environment. These thermoregulatory adjustments increase physiological stress and may lead to dehydration during prolonged exercise. Heat stress alone will impair aerobic performance when hyperthermia occurs. Dehydration in addition further exacerbates thermal and cardiovascular stress. In the following, some evidence-based points will be discussed, thanks to which the performance losses described above can be reduced.
Primary measure against loss of performance: acclimatization
Acclimatization is the most important intervention to reduce physiological strain and optimize performance. In this context, training sessions should last at least 60 minutes per day, induce an increase in both body core and skin temperature and further induce profuse sweating. Under these conditions, most adaptations take place during the first week of the heat stay, the others in the following two weeks. In highly trained athletes, the adaptations can take place up to twice as fast as in untrained athletes. Furthermore, the magnitude of the adjustments depends on the intensity, number, duration and frequency of the heat exposures. Acclimatization is particularly useful in an area with identical climatic conditions to the competition venue. If athletes do not have the possibility of an early arrival, they can train under artificially created, i.e. simulated, conditions. However, this procedure proved to be less specific despite similar physiological adaptations. Since the adaptations – and also their decay -, as so often happens, proceed differently from one individual to another, it is recommended to undergo an acclimatization process for a sufficiently long time before an important competition in the heat. Under certain circumstances, the individually optimal procedure may only emerge after several attempts.
Fluid and electrolyte balance
Although it is clear that excessive dehydration must be prevented, it is not possible to make any generalizations about the optimum amount to drink before, during and after the competition. This depends much more on personal fluid losses, fluid availability and other characteristics of the competition (e.g. duration). It makes sense to monitor the athlete’s hydration status over several days of exposure to the heat. To avoid unpleasant surprises, the electrolyte balance should also be controlled.
Cooling before and during sporting activity can increase sporting performance. Such strategies include cold water immersion or the cooling from body parts, ice slurries or the use of methanol. Radiation-reflecting, cooling, well-ventilated clothing with a high heat dissipation capacity, possibly also cooled, can also offer a benefit. Various cooling measures can be combined where possible, but should in all cases be tested and individualized during training to minimize disruption to the athlete.
Insight into research
In the next article we will give you an insight into the research: Severin Trösch, sports scientist at the Swiss Federal Institute of Sport Magglingen (EHSM) and expert on the subject of “heat” explains how associations and athletes can benefit from his work and which questions still need to be answered from a scientific point of view.
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 SwissOlympic. Trösch, S. Annaheim, S. Perret, C. Heyer, L. & Wehrlin, J. (2018). Wie bereite ich mich optimal auf Wettkämpfe in feucht-heissem Klima vor? Magglingen.
 Racinais et al. (2015). Consensus recommendations on training and competing in the heat. Scandinavian Journal of Medicine and Science in Sports, 25(1), 6-19.