Physical activity and exercise capacity assessments are measures of energy expenditure of an individual. Exercise capacity is an outcome measure, status indicator in health and diseases as well as a predictor of morbidity and mortality. Physical activity measures are seen as indicators of exercise capacity. However, the extent to which energy expenditure results derived from self-report physical activity can substitute physical performance tests remains inconclusive. This book presents a study on the relationship between physical activity and exercise capacity among young adults.