Even though I think it won't be safe to do something like this in real life, here's one of my forced exercise fantasies;

The lady in question is standing on a treadmill, wearing 6'' open toed high heels. She's pump gagged and her hands are bound behind her back. The nipple clamps on her breasts are tied to the handle of the treadmill. Then you start the machine and she has to keep up with it...