Question

2).We cannot stand at one place for a long time then how can we sleep on one place for 8 hours​

Answer 1

Because gravity is tough on us when we are vertical, first of all. Blood circulating all through the body has to get back to the heart continuously, and the feet are farthest away. Valves in the leg blood vessels open to help it pump upward and close to keep it from falling back down. That’s why our feet hurt so much when standing still for a long time.

Walkers/runners have an easier time because the motion helps keep blood circulating.

Lying down is easy. Gravity is exerting its force pretty equally along the body.

Answer 2

Answer:

because when we are sleeping our organs are in rest and don't work except the heart.but when we are standing the muscles are being use for a long time which causes pain in our body.