“Besides, massive amounts of exercise is not healthy for older folks.”
How much is massive?
That depends where you are at in your level of fitness. If you are just getting started then you are correct for many reasons. I'm 61 and have been a gym rat for a long time. I do massive amounts of exercise and I love it - and I'm quite healthy. Yes, you do need to protect your joints. This becomes more critical as you get older. Maintain good form. But my typical work out is two hours of intense weight training followed by a 5K run or 25 minutes of swimming. I do this 3 or 4 times a week. That's what I consider "fun". But I spent well over a decade working up to this.
Anything more than a walk around the park for an elderly person. Hiking maybe.
A person who is 20 lbs overweight should not be running a marathon until they have lost the weight. Training for a marathon requires 10 mile runs or longer with the feet and legs and body slamming against the pavement for hours at a time. That extra 20 lbs beats down on the joints.
Heck, even sitting on a bike seat may seem low impact but I believe that it is no coincidence that my serious back problems were the result of my very long rides that summer. Sitting for 3-4 hours on a bike seat is not good for the back.
Now if you are in fit and muscles are strong then the muscles will hold the frame together. That might have been my problem — my abdominal muscles were not strong.