Illustration: Shobu Tsuchiya

Summer Sports and the Fight against a Rise in Body Temperature

Due care and attention are needed to avoid increasing risk of heatstroke in association with outdoor summer sports. To protect your life, you should do exercises when it is relatively cool, for example, in the morning or evening, shorten the time of exercises and take in water constantly. This year, you are requested to wear a face mask to prevent infection. Wearing a mask in a hot and humid climate will increase the risk of heatstroke.

When you wear a mask, heat and humidity are trapped around the mouth and nose, and you may not feel thirsty, although this is dependent on the materials from which the mask is made. The risk of heatstroke and oxygen deficiency will increase while you are running. It is really dangerous.

If you run outdoors in summer, you should take off a mask or wear a well-ventilated, quick-drying fabric mask, run when it is relatively cool and avoid crowded areas. Take every possible measure to protect your body.

Your body temperature reaches as high as 39℃ at the finish line!?

When you run a marathon or long-distance race, you feel hot and sweat. The body temperature increases. It is natural when you burn up energy. During a marathon, the deep body temperature of runners is 37℃ at the start and increases to 39℃ after running the total distance of 42.195 km. They have a high fever at the goal. So, it is important to cool the body before and after, and during running.

We shed sweat to lower the body temperature. You must have seen marathon runners wiping sweat with sponge during the race in summer. If you wipe sweat, the wind blows directly against the body surface, facilitating heat evaporation. It is effective to pour icy water on yourself during the race to lower the body temperature. On the other hand, you should be precautious against hypothermia in a winter race. If heat loss by cold outside air or sweating exceeds heat generation by running, the body temperature falls, and hypothermia is caused. A sharp decrease in body temperature can happen after you reach the goal. Runners are wrapped up in a blanket to avoid heat loss.

Menthol produces a virtual sensation of coolness

Our body temperature is maintained at around 37℃ irrespective of an ambient temperature. In a hot climate, you sweat to discharge heat; in a cold climate, you produce heat inside the body. This process takes place not by your intention, but unconsciously, or by the autonomic nervous system. The autonomic nervous system protects your body.

TRP channels detect the body temperature. Different TRP channels in cells throughout the body are responsible for detecting temperatures of the outside air and all the things we touch. In a hot summer, you may feel cool by eating a mint tablet or smelling mint. It is because mint contains menthol, which activates one of the TRP channels, TRPM8.

The TRPM8 channel is activated by a temperature below about 25℃ and makes us feel cool. It is also activated by menthol. Even if the body temperature does not fall, menthol can produce a virtual sensation of "coolness," which tricks us into feeling cool. Attention! The body temperature will not fall with menthol. Do not overuse it. You should take water appropriately even if you feel cool and refreshed with menthol.

Click here to find out the secrets of TRP channels