Question

Why a man standing gets tired though he is not doing any work?

Answer 1

be specific...because he is not doing any PRODUCTIVE work
but he is taking energy from his body to stand otherwise he can sit or lay..
there is a difference between work and energy...
don't confuse in between the two..
work is zero
but energy will continuously be released out of his body till he is standing...and after that he will lay and accumulate energy

Answer 2

hey mate here is your answer ⤵⤵

As he utilizes the muscular force, His internal energy is used up, so a person standing for a long time get tired thought he does not appear to do any work as he is not moving.

Hope this will help you✌