Carla Langridge is a 76 year old personal trainer who can run rings around her grand children. She is still working more actively than most, was an opera singer in her youth and is a force to be reckoned with.
Maintaining muscle mass and bone density are a safeguard in an aging body. A certain amount of pride / vanity helps with motivation.
I live in a 76 yr old body, I bruise easily, have wrinkles and sunspots and do a 'crossword' after lunch. But I take no medication, no pills or potions of any kind. In that, I am an exception, but the reasons are not exceptional.
My weight and body fat are below average and I exercise 6 days a week -
only for 30 or 40 mins a day. I beat a hasty path to my physio if I feel something is not right, an injury at any age is a setback, but in old age it can soon become permanent.
Time or lack of it is the reason most people use for not exercising consistently. Not knowing what you are doing and the cost of joining a gym are others.