How and why does a person move?

We move thanks to the muscles that make bones flex and flex. A man laughs or cries, sings or talks, walks at a slow pace or runs skipping - all this is the “work” of the muscles.
The muscle may contract, i.e. become shorter. To stretch it, you need to use another muscle, which "straightens" the first. When contracted, the muscle moves the bone.

In order for it to return to its place, another muscle must contract.

Muscles are attached to the bones using tendons - strong white fibers. The largest muscle is the gluteus maximus. The one on which the person is sitting. Almost all tennis players have more developed muscles on the arm with which they hold the racket.

Muscles become larger if you constantly train them, that is, give loads. That is why athletes and people who want to be strong perform physical exercises for a long time.

What are cramps?

Cramps are involuntary muscle contractions. The muscle stops moving, as always, and it seems that it has hardened. It hurts. It is not yet known why the cramps occur, but they disappear if you rub the muscle hard or leave it alone for some time. Read our article: why are you jerking when you fall asleep?

The pain under the ribs after running is a cramp in the diaphragm - the respiratory muscle located under the lungs.