Check out the variations in bone density

You either use it or lose it. See the difference between a 40 year old triathlete, a 74 year old sedentary person and a 70 year old triathlete.

The take away message is? Consistency of movement keeps the body strong, resilient and youthful. The 70 year old has nearly the same muscle mass and bone density as the 40 year old because they never stopped physical movement/exercise.