Muscle is composed of muscle fibers, and each muscle fiber is composed of smaller myofibrils. Each myofibril is interwoven with two kinds of filamentous proteins (myosin and actin). It's protein.
Extended data
Muscle function
1, muscle is the guardian to prevent joint pain.
Our bones are like building blocks, and joints are where the building blocks meet. These building blocks can be built, fixed and held together by muscles and ligaments around the joints. Therefore, in order to stabilize the joint, it is necessary to practice the muscles around the joint. When muscles are strong, they can protect joints and prevent various joint injuries.
Take the knee joint as an example, there are many muscles around it to help the knee joint play a supporting role. If these muscles decline, the strength to support the body weight will be insufficient, the knee joint will become unstable, and we will feel pain in the knee joint.
Some middle-aged and elderly people or sedentary people often have low back pain. An important reason for this phenomenon is that they lack exercise for a long time, which makes their back muscles atrophy and their strength decline, and they can't fix the joints on their backs well, thus causing problems such as facet dislocation and disc herniation.
2. Muscle is a person's second heart.
The blood circulation of our whole body depends on the contraction of the heart, squeezing blood into blood vessels and then flowing all over the body. A healthy adult's heart can send 7 liters of blood in 1 minute, but because capillaries are everywhere in the body, it is not enough to rely on the heart as a "pump" to send the blood flowing into capillaries back to the heart. Especially the legs and feet, are farthest from the heart.
So it takes a long time for blood to flow from the heart to the toes and then back to the heart, and the feet are at the lowest end of the body, so it is difficult for the blood flowing down to flow back to the heart smoothly without enough pressure.
At this time, the muscles of the calf and foot are like' water pumps', which oppress blood vessels, make blood flow upward through venules and veins, and finally return to the heart, so that the whole blood circulation of the human body can be unblocked. Therefore, muscle is known as the second heart of human body. The more developed the muscle, the stronger the muscle contraction, the more it can promote venous blood to return to the heart and promote blood circulation.
3. An important factor of "lean physique"
Many women envy others that they can eat a lot, but they are not easy to gain weight. Different constitutions determine people's fatness and thinness, and one of the important factors is that each person's body contains different proportions of muscles.
Although fat meat and lean meat are both meat, muscle (lean meat) and fat (fat meat) have different ability to consume calories. When you are quiet, muscles of the same weight consume three times as many calories as fat. One kilogram of fat can only consume 4 calories a day, but one kilogram of muscle can consume 12- 15 calories. After various activities or exercises, muscles will consume more energy.
Reference source; Baidu encyclopedia-muscle