The scientists can tweak the intensity of the centrifugal force as well as decide whether to spin around a person's head or chest, but it's not clear just what will work. That's partly what the experiment is for -- they'll have a better sense of what gravitational effects would be necessary to prevent muscles from weakening.

Whatever the conclusions, you probably won't see 2001-style rotating habitats any time soon. You're likely to see something resulting from studies like this, however. If humanity is going to embark on trips to Mars or send more than a handful of people into orbit for extended periods, it will likely want some kind of simulated gravity to maintain the fitness of future spacefarers.