To reach their findings, researchers at the University of Texas in Austin compared the brains of 28 active people ages 40-65 to those of 27 sedentary subjects in the same age range. The subjects who exercised  ran and/or cycled at least four days a week.

Head researcher Andreana Haley, Ph.D. and her team measured concentrations of neural markers in the subjects as well as assessed their overall cognitive functioning. While results showed no differences between the groups in mental functioning, the subjects who exercised regularly showed higher measures of the neural markers.

"Our results indicate that regular physical exercise is associated with a healthier brain, better neuronal viability, greater neural plasticity and higher metabolic efficiency," Haley told Runners World in an interview on the study. "In other words, the brains of habitual exercisers appear to have a higher brain reserve and can be expected to age better, preserving cognitive function for longer periods of time."

The study was published last week in the journal Brain Topography.

In another study published Friday, researchers from the Karolinska Institutet and Stockholm University found that keeping physically fit can help add up to six years to a person's lifespan, making physical exercise the strongest predictor of survival. Results were published in the British Medical Journal.