Question

why do we tired on quick exercise

Answer 1

because as we go on doing the exercises our blood pressure increases in the sense the blood needs more oxygen as a result the our breathing ratr increase and more oxygen is transported so we get tired because of this fast mechanism

Answer 2

When we do quick exercise or quick movements then we get tired because the amount of oxygen that the our body needs when we are doing the exercises is not provided by the blood.

It occurs because it does not have the capacity to carry more oxygen than it actually does in its normal circulation so we get tired after doing exercises....