Research in mainstream psychology and sport psychology stresses the importance of a developmental perspective that considers continuity and change from infancy through older adulthood. Understanding age-related changes in perceptions physical competencies emotions social influences and achievement behaviours is critical in terms of developing theory enhancing the research knowledge base and devising applied programs to promote positive physical activity experiences for youth through older adults. This book demystifies this perspective for students and researchers and contributes interesting and innovative ideas for the field. The book examines the current sport and exercise psychology literature reviews mainstream theories from psychology and elaborates on how cognitive physical social and other developmental factors influence behaviours in physical activity settings. Section One reviews fundamental concepts and controversies. Section Two examines developmental issues in youth and adolescence such as parental influence competition and peer relationships. Section Three discusses young middle and older adulthood in terms of self-perceptions social influences motivational processes and self-regulation skills. Section Four covers expertise transitions moral development diversity disabilities and injury throughout the lifespan.