The location and function of human muscles

　　Muscles are widely distributed in the human body. There are about 520 muscles in the whole body, accounting for almost 40-50% of the body weight. It can be seen that human muscles are the main body of the body. Generally speaking, their names are based on muscle type, shape, position, function, etc.

　　There are 3 types of muscles：

　　One is a muscle controlled by human consciousness, called voluntary muscle；

　　The other type is muscles that are not controlled by human consciousness, called involuntary muscles (such as the muscles that transport food into the stomach)；

　　There is another type called myocardium, which is unique to the heart.

　　According to the position of the muscle , divided into chest muscles, abdominal muscles, psoas muscles, etc.； According to function, they are divided into flexor muscles, extensor muscles, etc. ；

　　by shape , divided into long muscle, brevis muscle, latissimus etc.； According to the number of muscle heads, they are divided into biceps, triceps and quadriceps. ； According to the direction of fiber arrangement, there are pennate muscles. Pennate muscles are divided into pennate muscles, semi-pennate muscles and multi-pennate muscles.

　　The following is a brief introduction to the location and functions of the main superficial muscle groups of the human body.

　　one, platysma It is the most superficial layer under the skin on the front of the neck. When contracting, the corners of the mouth are pulled downward and the neck is tightened. skin。

　　two, sternocleidomastoid muscle This is the most prominent superficial muscle in the neck. When the lower part is fixed, the action on one side can make the head turn to the opposite side and tilt to the same side. ； When the head is in a normal posture, the combined force of the muscles passes behind the transverse axis of the atlanto-occipital joint to flex the head forward. When fixing, lift the chest to help inhale

　　three, trapezius muscle It is located under the skin of the neck and back, with one side forming a triangle and the left and right sides joining together to form a trapezoid, called the trapezius muscle. When near fixation: the upper descending fibers contract, causing the scapula to lift, rotate upward, and retract. ； The middle transverse fibers shrink, causing the shoulder bone to retract (closer to the spine) ； The lower ascending fibers contract, causing the scapula to descend and rotate upward. ； The upper and lower fibers contract simultaneously, causing the scapula to move upward, such as an arm lift. When distally fixed: one case shrinks and flexes the head to the same side ； Contraction of the trapezius muscles on both sides straightens the head and spine. The strength of this muscle can be developed by using exercises such as barbell shrugs, straight-arm side raises with weights, and chest expansion with weights. When the trapezius muscle is fully developed, the muscle becomes shorter, pulling the shoulders back to make the shoulders wider, keeping the back straight, and tilting the head back. This can correct defects such as hunched back, buckled shoulders, and forward head extension, and give a correct upright posture. Well-developed trapezius muscles are a sign of fitness, strength and beauty, and are an advantage for amateur bodybuilders to participate in bodybuilding competitions.

　　Four, deltoid muscle Located under the skin of the shoulder. It is a triangular-shaped muscle that forms the bulging shape of the shoulder. The muscle fibers on both sides are spindle-shaped, and the muscle fibers in the middle are multi-pinnate. This structure of the muscle is small in size but has greater strength. When near immobilization, the anterior muscle fibers contract to flex and internally rotate the upper arm. ； Contraction in the middle to abduct the upper arm ； Contract the back and extend the upper arms. External rotation, the front, middle and back parts contract simultaneously to abduct the upper arm, such as a side arm lift ； Use exercises such as weighted straight arm raises and lateral raises to develop the strength of this muscle. Broad, powerful, rounded shoulders are the hallmark of an excellent bodybuilder.

　　five , latissimus dorsi Located under the skin of the lower back and lower back of the chest, it is the largest latissimus muscle in the body. The upper part is covered by the trapezius muscle. When nearly fixed, the upper arm is extended, such as swinging the arm backwards, and the upper arm can be adducted and internally rotated. When the body is far fixed, you can pull the trunk closer to the upper arm, such as horizontal bar pull-ups and other movements. Because some fibers of the latissimus dorsi originate from the ribs and can lift the ribs when they are distally fixed, they are also called inspiratory accessory muscles. Use horizontal bar pull-ups, backward pull-ups, prone rows and other exercises to develop the strength of this muscle. Latissimus dorsi helps improve body shape. When it is highly developed, it prominently reflects the width of the shoulders and thin waist, making the upper body more burly and in a "V" shape.

　　six, sacrospinalis muscle A long, slender muscle in the back is called the sacrospinalis. Located on both sides of the spine, like two large columns from the occipital bone of the head to the end of the spine (sacral bone), the spine is placed in the obvious concave groove between the sacrospinal muscles and is a powerful spinal extensor muscle. When the lower part is fixed, both sides contract at the same time to extend the head and spine, raise the head, raise the chest, and collapse the waist. ； When one side contracts, the trunk flexes to the same side, such as side flexion movement.

　　seven, pectoralis major It is a fan-shaped flat muscle located under the skin of the chest. It has a wide range and is divided into three parts: the clavicle, thoracic ribs and abdomen. When nearly fixed, the upper arm can be flexed, adducted and internally rotated. When far fixed, pull the trunk closer to the upper arm, such as jumping rope and climbing poles. In addition, this muscle can also lift the ribs and is an auxiliary muscle for inhalation. When the chest muscles are developed, the chest is high and breathing is more adequate and smooth. Exercises such as parallel bar swing dips, bench presses, and pull-ups can develop the strength of this muscle.

　　eight, serratus anterior It is located under the skin on the outside of the thorax, and its upper part is covered by the pectoralis major and pectoralis minor muscles. It is a flat muscle. When nearly fixed, the scapula can be extended forward and rotated upward. The strength of this muscle can be developed through exercises such as dumbbell lateral raises, barbell shrugs, and chest expansion with weights.

　　Nine, rectus abdominis Located on both sides of the midline of the anterior abdominal wall. When the upper body is fixed, the two sides contract to tilt the pelvis backward or maintain a higher horizontal position, that is, to tighten the abdomen. ； Bend the spine forward during lower fixation. The strength of this muscle can be developed using exercises such as sit-ups, supine leg raises, and supine sit-ups. Abdominal muscles are easier to weaken than other muscles in the body. When there is a lack of exercise, excessive nutrition, and a large amount of abdominal fat accumulates, the abdominal muscles are most likely to relax. Abdominal sagging (or sagging) and body fat are common symptoms of the human body. healthy A sign that the level is starting to fall. Well-developed abdominal muscles and "wavy" muscles are a sign of well-trained self-bodybuilding trainers.