ABSTRACT
This chapter describes the developmental changes in muscular strength/muscular endurance across the human lifespan and how these changes are influenced by maintaining an active lifestyle. It identifies gender differences in each component of health-related physical fitness. The most frequently identified components that make up health-related fitness include cardiorespiratory endurance, muscular strength and endurance, flexibility, and body composition. The chapter examines each of these components and changes to them that occur over the lifespan. It looks at the evolution of each, paying particular attention to how an active lifestyle affects them and examines both laboratory data and field-test performance data. Resistance training involves the use of various resistance exercises to enhance physical fitness or to increase muscular strength, muscular endurance, and power for sports participation. Few physical-fitness test batteries include flexibility among the test items because no single flexibility test can estimate total body flexibility.
