I write a lot about both brain health and fitness for work. Coffee might be great for both, I’ve learned; I’ve also been surprised by how linked your muscles might be to your dementia risk.
But only recently did I read that your poop timing might affect your mental sharpness and your workouts, too.
Yup – a paper published in the journal Sports Medicine and Health Science this month tested triathletes using something called a Stroop test (a cognitive test which asks you to, say, separate the word “blue” from the colour of the font it’s written in quickly) following laxative use.
This follows research done by the same scientists using the same participants that explored how their bowel movements affected their training.
Emptying your bowels seems to have brain and muscle benefits
In the 2024 paper, the scientists found that giving athletes a magnesium-based laxative before they took the Stroop test seemed to significantly improve their scores.
Calling it the “most striking finding of this study,” the scientists pointed out that the laxative didn’t seem to be the main factor behind the apparent mental boost, either.
“Even in the absence of magnesium oxide, defecation led to improved Stroop test results for 9 out of 13 individuals,” they write.
The researchers add: “The result of this study suggests an unexplored causal link between the state of the rectum and cognitive performance.”
Meanwhile, a 2022 article by the same researchers found that the same 13 triathletes had lower blood pressure when exercising after pooping, which might have led to their improved exercise endurance and decreased fatigue post-number two.
The best results seemed to come from those who voided their bowels between 60-90 minutes before either exercising or doing the cognitive test.
Why would that do... anything?
These studies have only suggested a link. They haven’t proven a causal relationship, and they have a small sample size of 13 triathletes.
Still, study author Professor Chia-Hua Kuo thinks that the associations he and his team have found suggest that the brain can “manage” cognitive and muscular demands better when they have fewer background tasks – like digestion – to pay attention to.
“When you do exercise, especially long-distance exercise, your brain is going to be sending high amounts of commands to the muscles,” he said.