What is the content of muscle contraction physiology?

Muscle tension is determined by the mechanical, anatomical and physiological conditions of muscle contraction. Load is the basic mechanical condition for muscle tension. Without load, muscles can't produce tension. The load can be weight, inertia force or other force. When muscles work, with the increase of load, the tension produced by muscle contraction also increases. The anatomical factor affecting muscle tension is mainly the size of muscle physiological cross section. The physiological cross-section of muscle is the sum of the cross-sectional areas of all muscle fibers. Other things being equal, the larger the physiological cross section of muscle, the more muscle fibers it contains, and the greater the tension it produces. The relationship between muscle tension and physiological cross section can be expressed by the relationship between absolute strength, specific muscle strength and physiological cross section. When muscles contract under a load that can hardly move, the maximum Zhang Liwei absolute force, that is, the maximum force exerted by muscles per square centimeter of physiological cross-section, is called specific muscle strength, which is equal to the ratio of absolute muscle strength to physiological cross-sectional area. According to the measurement, the specific muscle strength of human muscles is about 4 ~ 10. Obviously, the larger the physiological cross-sectional area, the greater the muscle strength. The physiological conditions that determine muscle tension can be attributed to the degree of neuromuscular excitement and fatigue, that is, the functional state of the nervous system. High-intensity strength training can improve muscle strength, largely because it improves the ability of the nervous system to regulate muscle work. Japanese physiologists have reported that the nervous system of trained elite athletes can mobilize 90% muscle fibers to participate in the work when they exert their maximum strength, while ordinary people can only mobilize 60% muscle fibers to participate in the work when they exert their maximum strength.