To investigate these effects, the researchers used a treadmill to precisely control exercise intensity and functional near-infrared spectroscopy (fNIRS) to measure activity in the prefrontal cortex after participants completed 10 minutes of very slow running at approximately 3–6 km/h, a pace close to walking, according to the University of Tsukuba website.

This comfortable pace corresponds to a very light exercise intensity of approximately 35 per cent of peak oxygen uptake (V̇O₂peak).

The study found that after just 10 minutes of very slow running, participants recorded a shorter Stroop interference time—a measure of executive function—and reported an improved mood.

Brain activity also increased in prefrontal regions associated with executive function and mood regulation, particularly the left dorsolateral prefrontal and left frontopolar cortices.

“Interestingly, greater up-and-down movement of the runner's head—the gentle vertical oscillation characteristic of running—was associated with a greater improvement in mood,” the University of Tsukuba said.

The findings suggest that even very slow running, despite placing relatively little physiological demand on the body, may simultaneously improve mood and executive function. The study also offers insights into the brain mechanisms that may contribute to these effects.