Question

why we feel tired after doing some exercise
given scientific reasons​

Answer 1

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We get tired after exercise because our muscle fibers get tired very quickly. This is due to the major source of energy for the muscle tissue, called adenosine triphosphate, or ATP. As the muscles make use of this supply of energy, they get tired and fatigue.

Answer 2

It's common to get tired after a long or tough workout. In general, this occurs because your muscles run out of energy. Your central nervous system also loses its ability to keep moving your muscles. This causes muscle fatigue, making you feel tired.

I think when u do any stress work take a nap..