I've had this fantasy for quite some time and when I say forced exercise I don't mean women doing push ups at Army boot camp nor swinging a pick ax in a coal mine at some WW2 concentration camp.

some silly examples:
a sorority initiation where the pledges have to work out till fatigue
discipline at an all girls school where forced exercise would be used as punishment
cheerleading tryouts where endurance exercises would be a requirement

The exercises would be aerobic type and not heavy weight training Maybe something like Jane Fonda style leg lifts (anyone remember the 80's) or hydrants, pelvic lifts, ect.

I know I can't be the only guy who has a thing for imagining a women getting all hot, sweaty, and fatigue from exercising. That's why they have women only health clubs