Most of this advice seems to be as important for people, especially after age 50. Example:
A dog's legs and spinal joints are only as stable as the muscles, tendons, and ligaments that cross these joints. For example, if muscle mass is lost in the hamstrings, quadriceps, and gluteals (the main muscles of the rear leg), then increased stresses occur at the hip, knee, and ankle joints, and this can lead to injury or worsen osteoarthritis pain.It seems the worst thing you can do for arthritic problems is to 'rest'. Strengthening the muscles with minimal pressure on the joints (while for example bending the knees) is key.
A pal who has had to stop pull ups and the like due to a heart condition has devised his own program of muscle exercises that have load bearing with minimal movement. He devised them form tai chi, which he teaches; they work; his doctor approves.
There was a news story recently relating muscle mass to mental capacity in older people. Cronies beware!