Every year at least 250,000 older Americans are hospitalized for hip fractures. It is hard to recover from a hip fracture, and many people lose their independence afterward. Low bone strength during the growing the years can lead to a greater chance of having a hip fracture as an older adult. Measures of muscle size are thought to be the best predictors of bone strength— muscles pull on bone and bone adapts by adding mass and changing shape to becoming stronger. However, accurately measuring muscle size is difficult. Researchers with the University of Iowa bone development study recently reported that a simple test often used in physical education classes, the vertical jump, could predict lower body bone strength, as well as give an accurate clinical representation of muscle size. The researchers measured vertical jump height in 303 adolescents (average age 17 years) and took three-dimensional images of the adolescents’ lower leg muscles and bones to determine muscle size and bone strength. Their finding opens the door for easy to administer school-based physical fitness tests that may someday alert youth, their parents, and their health care providers of fracture risk in later life. These findings also speak to the value of keeping youth in jumping sports like volleyball and basketball throughout high school.