How can men sit on their asses all day without moving?
Men have very powerful sets of sitting muscles developed by evolution that enable us to sit for extended periods of time without getting tired. In prehistoric times, it was often necessary to sit in one spot for extended periods of time while hunting for prey. The more successful hunters were able to sit very still for very extended periods of time thereby passing on this ability to their progeny. The figgidy types were all gobbled up by saber-toothed tigers and et cetera. The end result is that almost all modern men are born with this innate ability.