COMbined Exercise Trial (COMET) to improve cognition in older adults: Rationale and methods.

Substantial evidence suggests physical exercise may sustain cognitive function and perhaps prevent Alzheimer's Disease (1, 2). Current public health recommendations call for older adults to do at least 150 min a week of aerobic exercise (e.g. walking) and twice a week resistance exercise (e.g. weight lifting) for physical health. Yet, much remains unknown about how these exercise modalities support brain health independently or in combination. The COMbined Exercise Trial (COMET) is designed to test the combined and independent effects of aerobic and resistance training specifically focusing on exercise-related changes in 1) cognitive performance, 2) regional brain volume, 3) physical function, and 4) blood-based factors. To explore these questions, we will enroll 280 cognitively normal older adults, age 65-80 years, into a 52-week community-based exercise program. Participants will be randomized into one of four arms: 1) flexibility/toning- control 2) 150 min of aerobic exercise only, 3) progressive resistance training only, or 4) combined aerobic and progressive resistance training. Outcomes assessed include a comprehensive cognitive battery, blood biomarkers, brain magnetic resonance imaging, physiological biomarkers, cardiorespiratory fitness, physical function, and battery of psychosocial questionnaires is assessed at baseline, 6 and 12-months. COMET will provide rigorous randomized controlled trial data to understand the effects of the most common exercise modalities, and their combination (i.e., the standard public health recommendation), on brain health.