Whether for high-level athletes or Sunday athletes, any competition requires preparation and training. The goal is to be able to give the best performance on the right day. While amateur runners may join training groups to improve their running technique and increase their mileage, other athletes will consult a kinesiologist for a more advanced training plan, a physiotherapist for pain during training, and even a nutritionist for a nutritional plan. A multidisciplinary approach is best to help amateur athletes achieve their objectives, like running a first marathon. However, even with the use of all these wonderful professionals, certain factors specific to the competition can be neglected, such as environmental conditions. In Quebec, even with our temperatures, heat wave episodes can hinder competition by putting athletes at risk or by forcing the cancellation of events. For example, the Montreal Marathon was cancelled in 2017 due to a heat wave: the forecast temperature was 30°C, with the humidex at 39. This condition has nothing to do with the Hawaii Ironman, the Olympic Games in Rio or any other competition in a hot zone.

One of the differences between recreational athletes and Olympic athletes is the medical and scientific support system that is built around the professional athlete. The role of the exercise physiologist on a team is to educate coaches and athletes about potential training risks and to implement training while addressing environmental stresses such as heat. With the increasingly hot temperatures and the current training cycle for the 2021 Tokyo Olympics, there has been a great deal of research and development in exercise in extreme heat and humidity. Let's use this knowledge to better equip our recreational athletes and prepare them for a safer and more fun competition.

Consequences of heat on physical exercise

Heat during exercise can cause many symptoms such as headaches, extreme weakness, dizziness/vertigo, vomiting, and profuse sweating (Casa, 1999). Physiologically, temperature regulation (thermoregulation) becomes deficient, leading to dehydration, increased heart rate, decreased blood pressure, increased body temperature, and increased perception of exertion (Guy et al., 2014). It is therefore important to teach our athletes the previous signs and symptoms so that they can avoid the worst. In some cases, cardiac arrest can occur and be fatal. However, the treatment is very simple: complete rest, cooling (move to the shade and/or place cold compresses), and rehydration (Casa, 1999).

Ultimately, these consequences lead to a decreased performance, especially in long distance events. For elite athletes, heat can reduce marathon performance by 3.1% for men and 2.7% for women (Guy et al., 2014). It is important to consider that this decrease in performance is for highly trained individuals. Few research projects focus on the general population and it is therefore legitimate to hypothesize that this decrease in performance will be all the more marked in a less trained population.

How to prevent

There are many techniques to prevent the deleterious effects of heat during exercise. However, we will focus on two of the most accessible: heat acclimatization and hydration.

• Acclimatization to heat

There are many heat training protocols to help the body acclimatize. These are of variable duration and can be effective from 7 days of training. The participant must train at least once a day at an intensity greater than 50% of his VO2max, for a maximum of 90 minutes and, of course, in warm conditions (above 25° Celsius). Other training activities should be maintained, but it is very important to adjust volume, intensity, and recovery (Guy et al., 2014).

During the competition, the body temperature will remain the same. However, the increase in plasma volume, cardiac output, sweating rate, and exercise tolerance allows for better performance (Hargreaves, 2008).

You can set up a warm-up workout by sitting in a room and warming it up when you are active on an elliptical, a treadmill or a stationary bike. If you want to stay specific to the demands of the discipline, you can do the workout at the time of day when the temperature is highest.

It is very important to hydrate after these sessions and not during them to allow the stress to act and hope for physiological adaptations.

• Hydration

We don't need to go into details about hydration and its benefits for exercising. Here are some basic recommendations to give to your clients, taken from the American College of Sports Medicine's literature review on exercise in hot conditions (Casa, 1999):

1. Maintain good nutrition and hydration 24 hours before the event.
2. Drink approximately 500 ml of water 2 hours before the test to allow the body to excrete excess water.
3. Consume as much water as is lost through sweating during the event. If it cannot be measured, drink as tolerated.
4. Liquids must be cool, i.e. at about 15°C.
5. If the event lasts more than 50 minutes, you can add carbohydrates to your water by taking sports drinks.
6. For long trials, add salts and minerals to your drinks and do not drink too much to avoid hyponatremia, a fatal condition.

Key Message

Competition in warm conditions will be more and more frequent for recreational athletes. It is therefore important to teach them the signs and symptoms of heat exhaustion and how to intervene. In addition, with competitions becoming more and more difficult, our recreational athletes will need advice to better prepare themselves to perform in hot conditions. Two strategies are essential: to acclimatize to the heat and to hydrate well. This will allow them to finish their event with a smile and the desire to start again.