The human skeleton is strong and reliable, it is particularly reliable and durable. The structure of the bones allows them to withstand very heavy loads.
The skeleton and muscles grow and develop during childhood and adolescence. The most intense muscle growth and development occurs between the ages of 14 and 17.
For the correct formation of the skeleton, it is necessary that the body receives a sufficient amount of minerals, as well as vitamin D (which is produced in the skin under the influence of ultraviolet radiation from sunlight). With a shortage of this substance, children develop a disease – rickets. The bones become soft and can bend even under the weight of the body.
An increase in the load on the joints (due to obesity, when the body weight significantly exceeds the physiological norm) leads to joint diseases. At the same time, the pressure on the supporting surfaces of the joints of the lower extremities increases, the blood supply to the extremities worsens.
Physical education, sports, work activities contribute to the formation of the skeleton. This is due to the fact that the development of the skeleton and the muscles of the body are interconnected (the better the muscles are developed, the stronger the bones of the skeleton). In the places of attachment of the tendons of the muscles, the bones thicken, roughness and tubercles are formed on them.
Muscles need systematic training. With regular physical work, playing sports, they receive more nutrients and oxygen (with blood flow), muscle fibers grow faster, muscle mass increases, and a person becomes stronger.
Muscular work is also accompanied by changes in the activity of many organs and systems of organs: cardiovascular, respiratory (the supply of oxygen to tissues increases, biochemical reactions in cells are accelerated, metabolism proceeds more actively). This has a beneficial effect on the entire body, strengthens health, making a person hardened and able to withstand various adverse environmental influences.
Physical inactivity is a decrease in the load on muscles and a limitation of the general motor activity of the body.