Last week, Annie Tran, a runner who has completed six half marathons and two marathons, posted on social media that brushing her teeth with about 10 km remaining in a race pulled her back into contention.

"Any runner knows the 32 km mark is when you have to push and find any energy left," she wrote. "After brushing my teeth, I felt revived. Every breath was cool and minty, and that 'slight shock' helped me regain focus. I think I will never compete without it again."

Annie shared that she first tried a disposable toothbrush during a long work event. The feeling of a clean mouth pleased her, and she began carrying them while traveling. She then decided to try it on race day.

According to Canadian Running Magazine, no direct research proves that brushing teeth during a competition improves performance. Some studies even suggest that mint does not significantly impact athletic performance.

However, mint toothpaste can create a placebo effect (psychological)—similar to the phenomenon of "look good, feel good." The cool sensation stimulates the nervous system, providing sensory alertness and helping runners temporarily forget muscle fatigue.

Additionally, after hours of dehydration, consuming energy gels, and quick foods, a runner's mouth often becomes uncomfortable. Brushing teeth—much like splashing water on one's face at aid stations—can provide a refreshing and re-energizing sensation.

Disposable toothbrushes with toothpaste pre-applied to the bristles are considered the most convenient because they can be discarded immediately after use. However, those who wish to reduce waste can carry a reusable toothbrush with a small tube of toothpaste in their running vest or backpack.

Annie Tran is not alone; Courtney Dauwalter, an ultra-marathon legend, is also known for brushing her teeth multiple times during races exceeding 160 km. She considers this a form of "mental hygiene," helping her feel fresh after many hours of continuous running.

"Of course, legs are important in ultra-running, but the real key lies in the teeth," Dauwalter once shared with her sponsor, Salomon. "Brushing teeth mid-race is like taking a shower. I feel like a new person, and a surge of energy runs through my body."

This habit even led Salomon to launch an oral hygiene kit for runners, including a carbon toothbrush, carbohydrate and electrolyte-enhanced toothpaste, a mouth rinse bottle, and retractable dental floss.

For many runners, small details can determine the success or failure of a race—and sometimes, a toothbrush can become a "secret weapon" on the course.

Hong Duy (according to Canadian Running Magazine)