I mean, there's plenty you can do about it, it just takes effort. There are 80 year-olds running marathons. There are people past 40 playing professional soccer. You just need to take care of your body.
I agree and I do try to maintain my health as much as possible. But its also genetics. That 80 year old marathon runner is like saying you can become an Olympic athlete in your 30s as well. For every 80 year old marathon runner, there are a few hundred people like him who didn't make it.
When you get past 50, if your genetics are decent enough, you'll be able to last a long while. If you are just unlucky, things won't work out.
I have a family of 7 siblings and they are all terribly out of shape and unhealthy. I'm probably the healthiest person of all of us and I'm one of the youngest. Unfortunately, I'm approaching 50 and no matter how well I take care of myself (exercise, diet, no carb, no sugar, almost vegan diet, maintaining a healthy weight for my age) .... I still have early onset arthritis to the point where I can't move my arms.
Enjoy youth while you can ... you never know what you future body will have in store for you no matter what you do.
There's a little arch over the entrance to the living room in my home and post workout I'll often have a brainwave and go talk to my wife and I'll just instinctively rest my hands on that arch. I don't know why but it always feels natural to do that post workout