Skeletal muscle is one of the most dynamic and plastic tissues in the human body, accounting for about 40% of total body weight and containing 50–75% of all body proteins. Muscle mass depends on the balance between protein synthesis and degradation, which are influenced by factors such as nutrition, hormones, physical activity, and disease. This review discusses the structure and function of skeletal muscle, focusing on human skeletal muscle and recent research on single muscle fibers. The main functions of skeletal muscle include converting chemical energy into mechanical energy to generate force and power, maintaining posture, and enabling movement. From a metabolic perspective, skeletal muscle contributes to basal energy metabolism, stores substrates like amino acids and carbohydrates, produces heat, and consumes oxygen and fuel during physical activity. Skeletal muscle also serves as a reservoir of amino acids for other tissues. Reduced muscle mass can impair the body's ability to respond to stress and chronic illness. Various techniques have been developed to quantify muscle mass and study muscle function noninvasively, including urinary creatinine measurement, ultrasonography, CT, MRI, and DEXA. The review focuses on human skeletal muscle, emphasizing factors influencing muscle actions responsible for force generation. It discusses the basic structure, physiology, and mechanical properties of muscle, with a focus on limb muscles. The architecture of skeletal muscle is characterized by a specific arrangement of muscle fibers and connective tissue. Muscle fibers are multinucleated and post-mitotic, with each nucleus controlling protein synthesis in specific regions of the cell. Satellite cells are the adult stem cells of skeletal muscle, contributing to growth, repair, and regeneration. The review also discusses the dynamic nature of muscle tissue, including the effects of exercise, inactivity, aging, and pathological conditions.Skeletal muscle is one of the most dynamic and plastic tissues in the human body, accounting for about 40% of total body weight and containing 50–75% of all body proteins. Muscle mass depends on the balance between protein synthesis and degradation, which are influenced by factors such as nutrition, hormones, physical activity, and disease. This review discusses the structure and function of skeletal muscle, focusing on human skeletal muscle and recent research on single muscle fibers. The main functions of skeletal muscle include converting chemical energy into mechanical energy to generate force and power, maintaining posture, and enabling movement. From a metabolic perspective, skeletal muscle contributes to basal energy metabolism, stores substrates like amino acids and carbohydrates, produces heat, and consumes oxygen and fuel during physical activity. Skeletal muscle also serves as a reservoir of amino acids for other tissues. Reduced muscle mass can impair the body's ability to respond to stress and chronic illness. Various techniques have been developed to quantify muscle mass and study muscle function noninvasively, including urinary creatinine measurement, ultrasonography, CT, MRI, and DEXA. The review focuses on human skeletal muscle, emphasizing factors influencing muscle actions responsible for force generation. It discusses the basic structure, physiology, and mechanical properties of muscle, with a focus on limb muscles. The architecture of skeletal muscle is characterized by a specific arrangement of muscle fibers and connective tissue. Muscle fibers are multinucleated and post-mitotic, with each nucleus controlling protein synthesis in specific regions of the cell. Satellite cells are the adult stem cells of skeletal muscle, contributing to growth, repair, and regeneration. The review also discusses the dynamic nature of muscle tissue, including the effects of exercise, inactivity, aging, and pathological conditions.