There are two questions.
- at a certain age can you take it up for fitness.
- at a certain age can you still learn the art and implement it effectively in a stress situation.
The answer is not the same for both.
From my 33 years experience, at 20 you train through injuries, at 30 you train around injuries, at 40 you need rest to recover injuries, and some injuries you just learn to live with, and work around. That’s hen that broken wrist from your teens comes back to remind you, or your ruptured achillies tendon gets stiff every morning (as opposed to other elements of your anatomy), or when niggling back injuries become constant.
I think in your mid 40’s you reach your prime, as in, you may not be able to do all the athletic things the younger ones can, but what you do, you do so much better than they do, and you know the ins and outs to get the game into your paddock. Mid 40, its more about maintaining not increasing athletic skills.
And like Gene said, some arts change what they offer as you mature, as you get older, you discover the next level.
Problem is, if you start too late, you’ll never get enough of the training to take you there.
In my school, we let anybody, any age train with us for fitness. If they’re 40+ we tell them upfront that they probably won’t ever learn the full skill, but they will learn some, and get some fitness as well. But that holds true of some 20 year olds as well, they just don’t have the “stuff” to learn Pak Mei.
I know this is pretty much sweeping strokes, everybody knows an exceptional athlete of any age that can outperform their peers, but the facts seem to be that about 40, your body chemestry changes, metabolism and growth rate slow (injury repair), joints get worn out, things begin to break down in general. The chickens come home to roost.