Don't Shop Right After You Run a Marathon

We all recognize that performing endurance activity makes us tired. But we usually focus on the bodily sensations, especially those in our weary muscles. And maybe our chafing feat if it's a run. But what has been going on with our brain function during the running of something like a marathon?

Running Away With Executive Function

This was the question researchers Katherine Boere, Nevan Young, Rae Dauphinee, Frances Copithorne, Brett Kirby, Olave Krigolson, and Trent Stellingwerff from the School of Exercise Science, Nike Sport Research Laboratory, and The Canadian Sport Institute (Pacific) were interested in answering. They studied a sample of 16 women trained in endurance running before and after running the 2024 Victoria Marathon. This work was recently published in Medicine and Science in Sports and Exercise and is notable not just for the content but for an experimental approach that combines techniques across multiple scientific domains.

Using questionnaires, exercise physiological and neurophysiological measures they assessed working memory with electroencephalogram (EEG) recordings along with accuracy and reaction time assessments to measure cognitive performance and cognitive effort. Key measures were assessed within 10 minutes of marathon completion.

Running Requires Energy In

Their results revealed "a decline in high-load task accuracy and increased brain effort post-race, linked to low energy-availability risks". Changes were related to pre-event dietary energy status and energy intake during the marathon itself. These outcomes underscore that long duration exercise in a marathon, an extreme endurance activity practiced by many, temporarily compromises executive function. Quite importantly when considering the very large volume of training that precede actually running a marathon, this research shows significant energy deficits in the lead-up to race day. Critically, this research highlights "the importance of personalized nutrition strategies to maintain cognitive function during endurance events". To run more really does require eating more.

The Need to Feed

Indeed, the authors explicitly state that the deficits in cognitive performance are similar to those reported in amenorrhea and in those with anorexia nervosa ("prolonged energy deficiency and high rates of menstrual disruption"). The results in this work suggest that athletes who are chronically undernourished "may be more vulnerable to reductions in working-memory performance and must exert greater neural effort to meet task demands during prolonged physiological strain."

Takeaways from this work explicitly stated by the authors include "that working-memory performance is reduced and that cognitive effort is increased after marathon racing in trained female athletes, with these effects linked to both acute and chronic energy availability." Putting aside the additional effects that chronic energy deficits play in training and performance, their work clearly shows that working memory and executive function are compromised after running a marathon. Ensuring adequate energy intake during training and race day "may help preserve cognitive resilience, improve real-time decision making, and ultimately enhance both safety and performance in endurance competition."

After an endurance event your body and brain need fluids, food and rest. While you might grab something to eat on the way home, your cognitive capacity will be less than optimal. So maybe don't include a shopping spree if you stop at the mall.

(c) E. Paul Zehr (2026)