Experiments are showing that muscle loss caused by prolonged periods spent in zero gravity could be prevented (or at least lessened) by daily spins in a centrifuge. Just thinking about this makes me nauseated, so there goes being an astronaut.
Remember those "pillownauts"? Just like them, folks at the University of Texas Medical Branch at Galveston are spending weeks at a time in bed, except they're also spending an hour each day being spun around in a centrifuge designed by NASA. The idea is that creating an effect that feels like standing against "a force two and half times that of gravity" will assist in restoring muscle synthesis (and thereby possibly preventing muscle loss).