Physical inactivity is a major public health problem and a primary contributing factor to the obesity epidemic. While most Americans do not meet the physical activity (PA) guidelines (30 min/day, 5 day/wk), they do report watching several hours of TV each day, and frequently site "lack of time" as a barrier for engaging in PA. The Physical Activity and Leisure-time Study examines an approach convert sedentary TV watching into active TV watching time by having adults step in place during commercials (TV commercial stepping).