Research shows that heat exhaustion is more common in athletes who use nicotine

Olympic athletes with a nicotine addiction, beware. New research led by Brock has found that nicotine consumption – whether smoking, chewing, vaping or even wearing a patch – increases the risk of developing heat exhaustion during intense physical activity, especially if done in a warm environment.

The latest studypublished in the Journal of Applied Physiologyby Brock University Professor of Kinesiology Toby Mündel, carried out together with an international research team, comes just days before the opening ceremony of the 2024 Summer Olympics in Paris.

The findings are particularly relevant, because Mündel’s previous research has shown high nicotine use among top athletes. “Additionally, climate change has worsened summer temperatures in the Northern Hemisphere,” said Mündel, Canada Research Chair in Extreme Human Environments.

He says the last Summer Olympics in Tokyo, Japan, was “the hottest and most humid Olympics ever”, while the upcoming Games in Paris are expected to potentially break those records again.

Holding the Olympics in an urban environment with little green space and lots of pavement and concrete – which absorbs heat – increases the risk of heat exhaustion for athletes and the public watching, he says.

Mündel and his team wanted to find out whether nicotine increases body temperature – as measured by the temperature of the gastrointestinal tract – mainly by increasing metabolism or reducing blood flow to the skin.

Based on studies showing that former smokers tend to gain weight when they quit smoking, Mündel says they found that “nicotine appears to speed up a person’s metabolism, increasing the number of calories you burn.”

Other studies have also shown that nicotine constricts blood vessels, reducing blood flow to the skin. The blood supply to the skin allows the body to release heat and provides moisture for sweat. If this is restricted, the body can overheat, he says.

Ten male research participants who had never used nicotine wore a nicotine patch overnight and then repeated this with a placebo patch. Neither the participants nor the researchers knew when they received active and inactive patches.

The next day, participants cycled for an hour in environments of 20°C and again in 30°C. After each trial, researchers measured participants’ gastrointestinal and skin temperatures. The experiment was repeated four times.

Two participants had to leave the 30°C nicotine trials because one had reached the maximum ethical limit for gastrointestinal temperature and the other quit due to ‘nausea and chills’.

Through their various measurements of blood flow in the skin and gastrointestinal tract, the team concluded that nicotine use increases heat stress, leading to heat exhaustion, by reducing blood flow to the skin.

Mündel says the study’s results are relevant not only to athletes, but also to others who work in high-temperature environments, including military personnel, firefighters and some industries.

Mündel says that he is sometimes asked whether nicotine use among athletes should be completely or partially banned. He notes that nicotine stays in the body for a while, so banning it in the hours or days before a match may not be effective.

It’s crucial that athletes and audiences drink plenty of water and keep their hydration levels high, he says.