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08/05/2022
With many sporting events organised during the summer and temperatures reaching peak values, more and more research is undertaken to understand the physiological mechanisms which can be improved to maintain an optimal level of performance even during extremely warm conditions.
It is important to know the different effects of heat on human physiology and performance during physical activity to understand the necessity to find solutions. One of the first physiological mechanisms is the attempt of the body to maintain its usual temperature. It is done through an increase in blood flow to the skin. As a result, less blood is directed to the working muscles, meaning that muscles are working with less oxygen, which leads to a decrease in aerobic capacity. Moreover, heart rate increases to support the decreased oxygen delivery, which impacts performance as well.
As a result of the increased heart rate and more broadly the increase in oxygen needs in the heat, the energy consumption, as well as the intensity of the effort, is higher than a similar effort in a temperate environment. Moreover, heat influence the perception of the effort. Therefore, due to the thermic discomfort, altered fatigue sensation, and decreased motivation, performance is even more decreased. From this statement, several changes can be used to maintain performance in the heat.
It is important to stay hydrated due to the increased sweating rate allowing the body to cool down. It is important to avoid losing more than 2% of body weight during the effort as it would translate into high dehydration leading to a decreased performance. Moreover, if sweat losses are very large, it could lead to other harmful impacts, and could even be lethal. To have a general idea of your sweat rate during physical activity, you can calculate it. You simply need to weigh yourself once with the bare minimum of clothing before exercising and to write down every fluid and food intake. At the end of your exercise, weigh yourself a second time with the same clothing and use this equation:
Sweat loss in litres per hour = (Starting weight - Final weight + Drink/Food intake) ÷ Hours spent exercising
During the effort, go for drinks that are not overly sugary nor high in carbohydrates as it tends to limit fluid intake. Moreover, adding electrolytes to the drink can be beneficial due to the increased mineral losses through sweating. Finally, cold drinks were found to be beneficial to sports performance due to their sensorial effect resulting in a reduced fatigue perception.
After the effort, it is important to drink around 1.5 times the fluid losses preferably with a drink containing minerals. The basics of nutrition also apply in extreme conditions with the need to refill carbohydrate stores. Finally, a good protein intake is needed to support protein synthesis due to the increased protein degradation in warm conditions. This allows muscles to be correctly repaired and drives muscle adaptation.
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