Photo/Illutration Runners keep their masks on even in the sweltering heat in Tokyo’s Chiyoda Ward in May 2020. (Asahi Shimbun file photo)

People still need to take measures against heatstroke even if they are not wearing masks, especially when exercising under the blazing sun, according to experts.

The Japanese Association for Acute Medicine (JAAM), the Japanese Association for Infectious Diseases and two other medical groups issued the warning in revised guidelines on preventing and treating heatstroke during the COVID-19 pandemic, released on July 15 following a surge in new infections.

“The bottom line is the risk of developing heatstroke won’t change even if you aren’t wearing a mask,” said Jun Kanda, a doctor at Teikyo University Hospital who is also a member of the JAAM, regarding the revised guidelines compiled by his team.

Findings showed a rise in body temperatures did not change with or without masks during about an hour of light exercise or a roughly 20-minute jog in scorching heat, the guidelines noted.

Experts also pointed out in the guidelines that putting on masks may make wearers feel suffocated but does not actually raise the risk of heatstroke. They added that removing masks does not lower the risk, either.

The guidelines said people exercising in sweltering heat and those who are particularly vulnerable to heat--such as elderly people, young children and patients with a pulmonary disease--should continue using air conditioners and frequently rehydrating regardless of mask wearing.

“We want people to keep in mind that they still should frequently rehydrate and avoid spending long hours under the scorching sun to prevent heatstroke, even if they aren't wearing masks,” said Tetsuya Sakamoto, who heads the JAAM.