Originally Posted by Pleasurepays

i noticed you couldn't explain it. so i will help you...

its not about using or not using your "arms" - your forearms are disengaged, i.e. the muscles themselves. your forearms are used for grip and curling your wrist. unless you are gripping something for dear life while you do push ups, or somehow curling your wrists while you do pushups, you are not using them.