Are bigger bones stronger bones? Not necessarily, according to a recent NASA study that seeks to ensure healthy bones in astronauts.

A four-year study of the long-term effects of microgravity on the bones of International Space Station crew members showed that the astronauts, on average, lost roughly 11 percent of their total hip bone mass over the course of their mission.

The study also found that a year after each crew member had returned to Earth, much of their lost bone mass was replaced. However, the bone structure and density had not returned to normal and signs of hip strength had not recovered at one year, although it had increased slightly compared to post-flight levels. Researchers say it could take much longer than a year to regain the lost strength.