What do astronauts and people in wheelchairs have in common? Bone loss. Bones, especially those in the lower spinal cord and legs, weaken without the force of gravity on the skeletal system. In space travelers and those with spinal cord injuries alike, the loss in bone can lead to fractures, says Dr. Jay Shapiro, bone loss team leader for the National Space Biomedical Research Institute. However, a new drug may help slow or halt the decrease in bone density among astronauts and the wheelchair-bound. Shapiro and his colleagues are testing a medication called Zoledronate, part of a class of medications known as bisphosphonates that inhibit the activity of cells responsible for reabsorbing bone. Currently, bisphosphonates are used to slow bone loss in people with certain types of cancer.