computer games forum

It's mostly perspective. The titular character of The Great Gatsby was described as a young man in his early 30s. It's true that people will slow down in their 30s, but it isn't such a sharp decline that a person becomes unable to take care of themselves. There are also factors to consider like lifestyle and injuries sustained over the years.

There are exceptions like Fauja Singh:
https://en.wikipedia.org/wiki/Fauja_Singh
but without going to exceptions, I'm 43, can run for hours just fine, in Winter I carry pellet bags of 15kg each for about 200m, etc. And I definitely am not an athlete, so...