Why do we stretch when we're tired?

Why do we stretch when we're tired?
It improves our circulation and help us to relax.
To improve the flow of oxygen to the brain and other trunk organs.
good examine!
never thought about it :O
it's the lactic sour which makes the muscles stiff, if we sit rust for a long time... so we stretch and dissolve the lactic acid and out muscles become flexible again..
When you stretch and move around, your blood starts circulating better and deliver more oxygen to your brain and muscles. So that's why you need to stretch when your tired.