There are multiple factors that impact bone health, including birth weight, nutrition, medications for seizures and/or reflux, genetics, and physical activity. Targeted exercise to improve bone health in childhood can be sustained into adulthood, and childhood is the best time to promote bone health.
For people with a physical disability, activity is a lifestyle. It's something that can start in physical therapy, but it really is something that has to be carried over into their everyday lives. What has happened over the years is we're understanding the importance of mobility.