Where does fatigue come from?
It doesn’t come from the body. Even when people exercise to exhaustion, studies have shown that there is fuel left in the tank – one found there was enough energy left in muscle tissue for participants to have kept going for another seven or eight minutes. The brain puts the brakes on, stepping in to stop us from over-exerting and injuring ourselves long before we reach our actual limits.
According to the latest research, our physical endurance is determined by our “perception of effort” – how much work the brain thinks that the body has done. But the brain can be tricked. In Brazil, a group of scientists improved power output in cyclists by 10% by running a small electric current through the brain. Elsewhere, it has been shown that giving athletes incorrect information about the temperature can help them maintain their performance in hot conditions, and that lying to them about their split times can help them break personal bests.
In one study, Professor Samuele Marcora and colleagues asked people to pedal an exercise bike at a fixed pace for as long as possible. Unbeknown to the participants, a screen in front of them was flashing up subliminal images for 1/16th of a second at a time. Cyclists flashed images of sad faces rode for 22 minutes and 22 seconds on average. Those shown happy faces reported less perceived exertion, and rode for three minutes longer. Marcora now wants to develop a pair of goggles that could flash up this kind of image at athletes while they are out training.
Forcing ourselves to keep going also means ignoring all the signals from our body telling us to stop. This “response inhibition” is very mentally taxing, and it causes a substance called adenosine to build up in the brain. Adenosine is associated with the feeling of mental fatigue – it builds up when people run marathons or work on boring spreadsheets, or if they haven’t had enough sleep. Adenosine increases perception of effort. It is the enemy of endurance.
Mo Farah drinks a couple of espressos before a race, to reduce mental fatigue.
Caffeine blocks adenosine. This is why Mo Farah drinks a couple of espressos before a race, and why caffeine pills and gum have become an essential part of the long-distance runner’s pre-race preparation. You can also train your brain, by doing monotonous response- inhibition tasks before or during exercise. In the short term, this will make your performance worse, but in the long run your brain will learn to produce less adenosine, which will reduce perception of effort and increase endurance.
In one study, Marcora asked two groups of soldiers to do a time-to-exhaustion test, where they were asked to ride at a fixed percentage of their maximum until they couldn’t any more. After 12 weeks of training the control group’s time-to-exhaustion had improved by 42%. The other group performed a mentally fatiguing task alongside their physical training sessions. Their time to exhaustion improved by 115%.
Auditory versions of these tasks for smartphones are in the works, but you can replicate the effect simply by changing your training patterns. For your brain, running five miles after a hard day’s work feels like the last five miles of a much longer run. It offers a much better workout for your willpower. It’s mind over matter, and fortunately for athletes – from the elite to the amateur – the mind is much easier to manipulate.
This article was originally posted at The Guardian.
Photo credits: occoquanbayperformance.com
About the author
Amit Katwala is the author of The Athletic Brain out on 11 August. To order a copy, go to bookshop.theguardian.com.