Astronauts’ bones in space may experience bone loss equivalent to twenty years of aging after six months in space. In a report published in Scientific Reports, the researchers say that within a year of returning from duty, about half of the bone strength lost can be regained. Leigh Gabel, an exercise scientist at the University of Calgary, Canada, states that although bones lose strength in a non-gravity environment, they can be reshaped because they are alive and active.
Gabel and colleagues studied 17 astronauts, 14 men, and three women, with an average age of 47 years, who spent four to seven months in 10 spaceships. The team used high-resolution peripheral quantitative computed tomography (HR-pQCT) (which can measure 3-D bone microarchitecture at scales of 61 microns thinner than a human hair) to image the bony structure of the lower leg shinbone and the radius of the lower arm bone. The researchers took these images before spaceflight, immediately after the astronauts returned from space, six months after they returned, and one year later. They used the values they obtained to calculate bone strength and density.
After less than six months in space, astronauts regained their bone strength from before going into space a year after returning to Earth. But those who stayed longer in space experienced permanent bone loss in their tibia, equivalent to ten years of aging. Gabel says there is almost no loss of lower arm bones, probably because of the weight training. Exercise scientist Steven Boyd of Calgary says lifting weights in space can help alleviate the bone loss. Gabel, Boyd, and their colleagues, who are part of a NASA project to study the effects of a year in space on the body, also hope to gain insight into how staying in space for more than seven months primarily affects bones.