Effects of Endurance-Focused Physical Activity Interventions on Brain Health: A Systematic Review.

Physical activity intervention studies that focus on improving cognitive function in older adults have increasingly used magnetic resonance imaging (MRI) measures in addition to neurocognitive measures to assess effects on the brain. The purpose of this systematic review was to identify the effects of endurance-focused physical activity randomized controlled trial (RCT) interventions on the brain as measured by MRI in community-dwelling middle-aged or older adults without cognitive impairment. Five electronic databases were searched. The final sample included six studies. None of the studies reported racial or ethnic characteristics of the participants. All studies included neurocognitive measures in addition to MRI. Five of the six interventions included laboratory-based treadmill or supervised bike exercise sessions, while one included community-based physical activity. Physical activity measures were limited to assessment of cardiorespiratory fitness and, in one study, pedometer. Due to the lack of adequate data reported, effect sizes were calculated for only one study for MRI measures and two studies for neurocognitive measures. Effect sizes ranged from d = .2 to .3 for MRI measures and .2 to .32 for neurocognitive measures. Findings of the individual studies suggest that MRI measures may be more sensitive to the effects of physical activity than neurocognitive measures. Future studies are needed that include diverse, community-based participants, direct measures of physical activity, and complete reporting of MRI and neurocognitive findings.