The anatomical analysis of movement is also the anatomical part of human kinematics (see sports biomechanics), which aims to analyze the regularity of movement from the perspective of human structure and provide theoretical basis for learning and improving the quality of movement.
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Although there are many kinds of movements, from the perspective of human structure, there is a certain regularity. Any action is driven by muscle contraction, pulling bones and movement around joints. Bones and joints are passive parts of movement, while muscles are active parts. Muscle plays an important role in human movement. When analyzing sports movements, the focus is on muscles. Therefore, before the action analysis, we must first understand the role of muscles.
Muscle is made up of many muscle fibers. When doing movements, muscle fibers can be shortened and passively stretched, and they can be in a state of neither shortening nor stretching. The work done by muscle fibers in shortened state is called inhibitory work, which is more common in sports. For example, when the deltoid fiber contracts, the arm can be raised horizontally. The work done when the muscle fiber is stretched is called concession work, and the work done when the elbow bends slowly under load to stretch the triceps brachii fiber behind the upper arm belongs to this category. When doing restraint work and concession work, the limbs are in motion, so this kind of work that produces movement is also called dynamic work. On the contrary, another kind of work is static work, that is, the length of muscle fiber remains unchanged, neither shortening nor stretching, but the tension of muscle increases. For example, when the arm is held horizontally, the length of the deltoid fiber remains unchanged, but its tension increases to overcome the gravity of the drooping arm, which belongs to this category.
The movement of each joint is not simply completed by a muscle, but by a group of muscles. In this muscle group, the function of each muscle is not exactly the same. Among them, the muscle that directly completes the action is called the prime Mover, and the muscle with the opposite function is called the antagonistic muscle. For example, in elbow flexion, the biceps brachii, the brachialis muscle in front of the upper arm and the brachioradialis muscle outside the forearm are the prime movers of elbow flexion, while the triceps brachii behind the upper arm is the antagonistic muscle of elbow flexion, and its muscle fibers are elongated but maintain a certain tension, thus preventing the prime movers from being injured due to excessive exercise. Sometimes to do an action, you only need to move one joint, and the adjacent joints are required to be fixed. In this way, the muscles of this joint can give full play to their strength. This kind of muscle that fixes adjacent joints is called the fixed muscle. If elbow flexion requires shoulder joint fixation, the muscles around the shoulder joint are called fixed muscles.
When analyzing movement, we should pay attention to gravity and friction besides muscle contraction. These forces are generated outside the body, so they are called external forces. Muscle contraction force is generated inside the body, so it is called internal force or muscle strength. Internal and external forces often act on the human body at the same time, in the same direction or in the opposite direction.
If the two forces on the limb are in opposite directions and the muscle strength is greater than the external force, the movement direction of the limb is opposite to the external force. For example, when running with high legs, the thigh bends upward at the hip joint, and its motive force is the iliopsoas muscle and rectus femoris muscle on the opposite side of gravity (Figure 1). If you squat with a heavy load, your body needs to be straight up from the squat position. At this time, in order to overcome the downward movement of the barbell and all parts of your body, the main muscles for squatting are gluteus maximus, quadriceps femoris and triceps brachii (Figure 2). If the two forces acting on the limb are in the same direction, the limb moves faster, and its prime Mover is the muscle group located on the same side of the limb movement direction. For example, when a volleyball player jumps up for a frontal spike, the upper limb stretches and contracts at the shoulder joint, and its gravity also makes the upper limb downward, so the speed of adduction and extension of the upper limb exceeds the speed of gravity downward. At this time, the prime mover of spike action is the muscle group that makes the upper arm stretch at the shoulder joint, namely pectoralis major, latissimus dorsi and deltoid (Figure 3). If the two forces act on the limb in the same direction and the movement speed of the limb is slower than the specific force, then the prime Mover is the muscle group located on the opposite side of the limb. For example, when the arms are slowly flexed and stretched on the parallel bars, the upper arm stretches and stretches at the shoulder joint, and gravity also makes the upper arm stretch and stretch at the shoulder joint; In order to improve the training effect and make the falling speed of the body less than the gravity speed, the prime movers are pectoralis major and latissimus dorsi on the opposite side of the limb movement direction, even if the upper arm is flexed in the shoulder joint.