That being said, one of the toughest guys I know (everyone has that toughest-guy-they-know) is in his mid 50s. A little ex-military Persian Muay Thai instructor that can pick apart, outlast and destroy the fittest and/or youngest in the class. Took him out for an 8k weighted run (kettlebell run with stops to do swings/snatches) and it didn't phase him very much. Another is an ex-SAS guy pushing 60, still rucks like he's 20 and does sledgehammer/tire work like a machine for HIC. So I don't know about old farts...but maybe tough cunning old bastards is more of a fit.
Certainly the guys that KB mentions here are extreme outliers, but there is a general point to be here. Those guys were probably extreme outliers their entire lives, and they are carrying it on well into their middle-age. Maybe the ex-SAS guy's time in a five mile ruck is a bit slower than when he was in his twenties, but he can still cover the ground along with all the other awesome stuff he has always done. I've see a lot of guys on forums panicking as their 30th birthday approaches (I find that really funny), as though they can expect to fall completely to shit on that day. The same thing, even more so, as they approach 40. I think we are so obsessed with youth here in the West that we way overplay the debilitation that must come with aging, or at least we expect it to happen so much earlier than it has to.
I'm not saying I'm anything near as awesome as the mofo's that KB mentions, but my case fits that pattern. I turned 43 in two months, and I don't feel like I've really slowed down very much. Just the opposite really. Sure, I don't hammer the weights for ME workouts four times/week like I did when I was in my twenties and early/mid thirties, but I also walked around as an overtrained, injured, and generally beat up semi-invalid for many of those years. Sure I don't load my back as often or as heavily as I used to, but I don't feel like that's a function of my age, but really just the consequence of some stupid behavior. If I hadn't picked up stress fractures in my lumbar playing American football, I bet there would be no problem for me. I have "slowed down" in some ways not because of my age, but because realized that I was doing a lot of dumb ass things. In other words, its injury accumulation, bad mobility patterns, and such that I picked up from poor training for decades, and not my age, that I think causes me problems. I do better on auto-regulated programs with more days off now, but I probably would've done better on such programs back when I was a younger man. In terms of my intensity of conditioning, mobility, strength relative to my bodyweight, body composition, endurances, etc., etc., etc., I am absolutely better than I've ever been, and I'm only getting better. Now I've thrown in martial arts for the first time in my life (or at least since I stopped wrestling as a kid), and that has only been positive.
Of course I'm going to fade, and so will the exemplars KB mentions. That's is the way of all flesh. No doubt, my actual performance in my 40s is short of what an equally well-trained athlete in his twenties can do. For example, I simply cannot match the college wrestles I sometimes workout/roll with in terms of speed and agility. Their speed beats me. That performance dip is far less than you might think; I can absolutely hang with (or sometimes out perform those same college wrestlers in terms of strength, endurance, and anaerobic capacity -- they have to work dam hard to beat me. In short, in terms of your work capacity, strength, and endurance, my experience is that you will fade a lot more slowly (if at all!) than you think. My point is that threshold can be pushed far deeper into our middle age or even senior years than our youth obsessed culture would have us believe!
Now maybe in November I'll fall part on my 43rd birthday, but I'm not betting on that!
