The Second Edition is designed for final year students and graduates studying kinesiology, exercise science, physical education, public health, health promotion, preventive medicine and human biology. It looks at the health benefits associated with a physically active lifestyle and a moderate level of fitness versus the potential deleterious consequences of physical inactivity. The book focuses on the prevention of diseases and enhancement of quality of life and well-being. It does not deal with the role of physical activity in the treatment of diseases and rehabilitation and is not intended to be an encyclopedic review of the field. Instead, each chapter provides an overview of the key concepts and the most important findings emerging from a collection of studies, discusses the limitations of the current knowledge base and identifies research needs. It highlights the link between physical activity and health.