I would say they are either quite lucky, or lying.
I know lots of folks my age, or older and 90% of them have some chronic physical ailment that limits their activities in some way that is generally the result of some old injury that wasn't properly treated. Whether it was my dad with all his leg, hip and back troubles from a dislocated hip in high school football that was not properly reset, or my mom's bursitis in her shoulder from a header she took while speed skating in high school, my own knees and ankle from stuff I did to them playing volleyball and racquetball in college, none of which were treated properly or given time to heal properly. We all "rubbed dirt on it and walked it off" and later we had a hard time walking as a result.
I'm having lunch today with a high school buddy who recently had back surgery to fix a disc he damaged in a motorcycle wreck in high school and didn't properly rehab when it happened. I can go on like this all day with stories of old injuries that people now suffer from.