The number and scope of established health-related benefits from physical activity continue to expand. Notable recent additions include improved weight status and bone health in children 3–5 years of age, prevention of excessive weight gain among adults, reduced risk of dementia, and improved cognition and a variety of other brain-health benefits. Greater flexibility in receiving health benefits is also apparent. No threshold of moderate to vigorous physical activity (MVPA) must be exceeded for benefits to accrue; small increments by individuals performing little to no MVPA produce larger reductions in risk than similarly sized increments in individuals already performing greater amounts of MVPA, bouts of MVPA <10 min in duration contribute to the accumulation of MVPA, and light-intensity physical activity can benefit individuals currently doing little or no MVPA. MVPA is indirectly related to the adverse effects of sedentary behavior. The definition of physical activity continues to be debated.
Powell is retired from the Centers for Disease Control and Prevention, Atlanta, GA. Blair is with the Arnold School of Public Health, Depts. of Exercise Science and Epidemiology/Biostatistics, University of South Carolina, Columbia, SC.