New study provides further proof that endurance fatigue is regulated by the brain.
Past research by Toby Mundel at Massey University in New Zealand has shown that cold fluids consumed during exercise in a hot environment improve performance more than warmer drinks. You might assume that cold drinks achieve this effect by keeping the body cooler. But there’s another possible explanation that Mundel explored in a new study.
In this new study, nine subjects rode stationary bikes to exhaustion at moderate intensity in a hot environment on two separate occasions. They were given a fixed amount of cool water to drink during both rides, but during one ride they were also given a menthol solution to swill and spit out every 10 minutes, while in the other they were given a placebo to swill and spit. Menthol, as you probably know, creates a perception of coolness on the tongue. Mundel wanted to see if swilling a menthol solution might improve endurance performance in the heat by essentially tricking the brain into thinking the body was cooler than it really was.
And guess what? It did. Eight of the nine subjects rode 9 to 12 percent longer in the menthol ride. While their body temperature was the same in both rides, the menthol ride felt easier to them.
This fascinating finding provides further evidence in support of the notion that the brain determines when fatigue occurs during exercise based on feedback signals from the body. The brain uses this information to predict how long exercise can continue before a catastrophic physiological breakdown (such as overheating) will occur and forcing the athlete to stop short of this point.
This effect is mediated on a conscious level through perception of effort. It is now understood that the feeling of fatigue is fatigue itself. This is why exercise performance can be enhanced through manipulations that affect the perception of effort without affecting any physiological parameters such as heart rate, blood lactate level, etc.
Published in the European Journal of Applied Physiology, Mundel’s new study is similar to previous work by Asker Jeukendrup, who showed that swilling and spitting out a carbohydrate solution enhances exercise performance by stimulating a reward center in the brain and thereby reducing perceived effort.