“Why does a 30-year-old hit their foot against the curb in the parking lot and take a half step and recover, whereas a 71-year-old falls and an 82-year-old falls awkwardly and fractures their hip?” asks James Richardson, M.D., professor of physical medicine and rehabilitation at the University of Michigan Comprehensive Musculoskeletal Center. For the last several years, Richardson and his team set out to answer these questions, attempting to find which specific factors determine whether, and why, an older person successfully recovers from a trip or stumble.