Skeletal muscle is a highly dynamic and plastic tissue, comprising approximately 40% of total body weight and 50-75% of all body proteins. Its mass depends on the balance between protein synthesis and degradation, influenced by factors such as nutrition, hormones, physical activity, and disease. This review covers the structure and function of skeletal muscle, including its cytoskeletal architecture, excitation-contraction coupling, energy metabolism, and force generation. The discussion focuses on human skeletal muscle, particularly single muscle fibers, and highlights recent scientific literature. Skeletal muscle plays crucial roles in mechanical functions, such as generating force and power, maintaining posture, and producing movement, as well as metabolic functions, including energy metabolism, substrate storage, and heat production. The review also discusses various techniques used to quantify muscle mass and function, emphasizing the dynamic nature of muscle tissue under different conditions, such as exercise, aging, and pathological states. The basic structure of skeletal muscle is characterized by muscle fibers, satellite cells, and connective tissues, with each fiber containing multiple nuclei and a complex protein network connected to the internal myofilament structure.Skeletal muscle is a highly dynamic and plastic tissue, comprising approximately 40% of total body weight and 50-75% of all body proteins. Its mass depends on the balance between protein synthesis and degradation, influenced by factors such as nutrition, hormones, physical activity, and disease. This review covers the structure and function of skeletal muscle, including its cytoskeletal architecture, excitation-contraction coupling, energy metabolism, and force generation. The discussion focuses on human skeletal muscle, particularly single muscle fibers, and highlights recent scientific literature. Skeletal muscle plays crucial roles in mechanical functions, such as generating force and power, maintaining posture, and producing movement, as well as metabolic functions, including energy metabolism, substrate storage, and heat production. The review also discusses various techniques used to quantify muscle mass and function, emphasizing the dynamic nature of muscle tissue under different conditions, such as exercise, aging, and pathological states. The basic structure of skeletal muscle is characterized by muscle fibers, satellite cells, and connective tissues, with each fiber containing multiple nuclei and a complex protein network connected to the internal myofilament structure.