It turns out that defecation before exercise has a surprising effect on cognitive function and athletic performance

Two recently published studies have found that defecation before exercise may lead to smarter decisions and improved sports performance, meaning that defecation may have important implications not only for improving sports performance but also for understanding cognitive decline.

Defecation after magnesium supplementation enhances cognitive performance in triathletes - ScienceDirect
https://www.sciencedirect.com/science/article/pii/S2666337624000404

Pooping makes you a better racer | EurekAlert!
https://www.eurekalert.org/news-releases/1066556

Pooping Before You Exercise Has an Incredible Effect on Performance : ScienceAlert
https://www.sciencealert.com/pooping-before-you-exercise-has-an-incredible-effect-on-performance

A research team led by biochemist Chen-Chan Wei of Taipei University conducted an experiment with 13 triathletes, who were asked to respond to a question by the color of the word 'red' displayed in blue, rather than by the meaning of the word itself, to measure cognitive flexibility and reaction time.

The results showed that using laxatives to defecate significantly improved scores on cognitive tests. The research team reported, 'The most noteworthy aspect of this study is that all participants who took magnesium oxide showed a clear improvement in their performance on the Stroop test. Even more interestingly, even in the cases where no laxatives were used, 9 out of 13 participants showed improved performance on the test after defecation.'

A 2022 study found that early Parkinson's disease patients showed mild cognitive decline when constipated, suggesting a link between the gut and the brain. According to science media ScienceAlert, the findings are not surprising, as the gut contains hundreds of millions of nerve cells and the gut microbiome is known to affect mood, the nervous system, and mental health.

Wei and his team also decided to explore this connection from the perspective of athletes in triathlons, a grueling competition that involves swimming, cycling and running and requires athletes to use their quick thinking, endurance and overall ability to outperform other athletes.

The research team had already found that defecation before a cycling race improves athletes' performance and increases blood flow to the prefrontal cortex, so the next step was to see if it also had a beneficial effect on cognitive function, in the same way that fasting improves physical performance.

'When you're exercising, especially during long-distance competitions, your brain is constantly sending out loads of commands to your muscles,' says Professor Chia-Hua Kuo, a physiologist at Taipei University. 'In fact, whether you can sustain your exercise is less about how much energy your muscles have left and more about whether your brain can keep controlling your muscles.'

In the study, 13 triathletes were asked to perform the Stroop test three times: first without a bowel movement, second after one hour of defecation after dietary control, and third after 13 hours of taking magnesium oxide and one hour after defecation.

As a result, more than two-thirds of the participants performed better in the second test. Furthermore, all participants who used laxatives performed better in the third test. Although the number of participants was small, these results strongly suggest that defecation may lead to improved cognitive function.

The researchers believe this phenomenon has to do with the allocation of limited resources in the body. When there's food in the digestive tract, blood and oxygen are used to process it. Conversely, when there's nothing to digest, those resources can be redirected to other functions. In fact, a lack of resources during exercise is thought to be the cause of a phenomenon known as 'runner's diarrhea,' when athletes suddenly find themselves unable to hold their bowels in during intense exercise.

A 2012 study argues that 'during exercise, the sympathetic nervous system shifts blood flow from the viscera to active muscles. Significant reduction in visceral blood flow can lead to gastrointestinal ischemia, or insufficient blood flow. 'In other words, the body shifts blood away from the digestive organs to accommodate exercise, which can have a variety of effects on the digestive tract.

'The human body is incredibly interconnected,' Kuo said. 'Our mental activity is not just in our heads, it's in every part of our body. And the rectum is also part of the brain.'