The thing is, you can be a marathon cyclist, hiker, racquetball playing, fencing fool (as I was) and one relatively minor incident can leave your abdomen looking like shredded hamburger inside.
Three major surgeries later I can (mostly) move like any uninjured person but I'm carrying about 50lbs of extra weight due to steroids, enforced sedentary lifestyle, and my own carelessness. I'm making decent progress back into a proper weight range now but I'll never again be where I was pre-injury no matter how much I exercise 'cause the damage was just too much.
Sometimes you don't get a choice in the matter of physical fitness. In fact the older you get the less choice you tend to have.
That's when you have to get smarter and figure out what is going to compensate for what time and nature may have taken away.
"The dogs may bark but the caravan moves on"