Oct 262016
From the excitingly-titled:
Results.
Paraspinal lean muscle mass, as indicated by the FCSA, decreased from 86% of the total PSM cross-sectional area down to 72%, immediately after the mission. Recovery of 68% of the postflight loss occurred during the next 6 weeks, still leaving a significantly lower lean muscle fractional content compared with preflight values. In contrast, lumbar IVD heights were not appreciably different at any time point.
Conclusion.
The data reveal lumbar spine PSM atrophy after long-duration spaceflight. Some FCSA recovery was seen with 46 days postflight in a terrestrial environment, but it remained incomplete compared with preflight levels.
Short form: long-term microgravity is bad for you. Solution: use some form of artificial gravity if you are in a space station or long-range spacecraft; or get there lickety-split if you’re traveling somewhere. Both are good.