Humans built these machines to help them avoid physical exertion. Then our butts began to expand like Jiffy Pop. So we built machines that required physical exertion and became slavishly devoted to them. But that's a story for a writer who cares about our society's soul. And we all know that things you can't mention in polite company are the only things worth discussing.
Muscles are very important.
The stronger you are, the easier it is to overpower other women at the vending machine and wrestle away their Reese's Sticks. But women have muscles you won't see them working on in the gym. Learn to work the PCs and not only will you age better, your man will look at you like he is Columbus and you are America. This beats the bejesus out of a nice bicep. You can do kegels anytime, anywhere.