Compare muscle contraction to a game of tug of war.

Even though muscle contraction and tug of war might seem similar, they are quite different. The muscles after being pulled eventually come to their place but in the tug of war the participants do not come back to their original position.

Explanation:

Muscle contraction is a phenomenon where muscles are actively pulled in response to force applied. Whereas, the in the game tug of war the rope is being pulled and force is being applied.

The flow of blood increases to the muscle when the activity increases. The constant push and pull of the muscles increases the temperature of the body.

In tug of war the rope if pulled from both the sides will eventually tear off, whereas when it comes to muscles, the force must be extreme.

the speed increase from w to x due to increased gravity force

the speed decreases from x to y due to decrease in gravity