Traveling by plane isn’t always easy on the body. And neither is space travel. Astronauts often experience atrophy, the loss of bone and muscle, during their months living in space’s zero gravity. People on Earth also tend to see their bones and muscles weaken as they age, increasing risk of injuries from falls. Companies like Elon Musk’s SpaceX and Jeff Bezos’ Blue Origin are working to open space travel for more people. And figuring out how to reduce atrophy — a condition that affects space explorers as well as senior citizens on Earth — is on the mind of scientists. At the University of Cen…