ABSTRACT
This chapter discusses the components of cardiorespiratory fitness change across the human lifespan and how these changes are influenced by increases in physical activity. It also discusses the developmental changes in muscular strength and muscular endurance across the human lifespan and how the changes are influenced by maintaining an active lifestyle. Cardiorespiratory fitness is the efficiency of the heart, lungs, and vascular system in delivering oxygen to the working muscle tissues so that prolonged physical work can be maintained. An increase in the level of physical work brings a corresponding increased need for oxygen among the active muscles. Minimal muscular strength is important because the contraction of skeletal muscle makes human movement possible. The decrease in joint mobility with age is partly caused by physiological changes to the structures that make up the joints: tendons, ligaments, muscle, synovial fluid, and cartilage.
