Yesterday I changed my desk in the office. I always had weak muscles as pretty much all physical exercises are forbidden by my doctor (if I want to keep my retinas in place). Still, I could barely lift a display from the desk and before it wasn't a problem. So I just ask the colleagues to move it for me.
Muscle loss is one of the effects of becoming a woman. The weight distribution is quite different: more water and fat, much less muscles. I wouldn't even believe that both my arms and legs could get any slimmer. Well, I'm glad I was wrong :-) .
You have two options: try to exercise (effect will be small and slow) or find someone else to do it (my solution :-) ).