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47 yo black belt 1 stripe, been at it for 17 years since starting at 30. The significant injuries are a complete ACL tear a few years ago and C4-C7 herniations that cause some numbness that's mostly been manageable. The grip tendonitis is there sometimes, and I've effed up my thumbs jamming them pretty hard at various times over the years. But a lot of these injuries...could have been any sport. I coulda blown an ACL playing basketball or tennis or something.
The thing I learnt from BJJ is the decline of the body during the 30s. I was paying attention to what my body was telling me. At 32, you think you are young forever. At 34, you start having pains that last longer than the night and you think ah I must have gone too hard or whatever else and you can tend to ignore it. At 36, it becomes undeniable what's happening- age. At 38, if you don't change your game, you will enter a state of semi-permanent injury. At 40, your cardio suddenly goes. I've seen students and teammates go through this, many didn't listen, I guess they thought they were immortal or something.
One of the things that helped me most in BJJ was just not doing it as much. I was a 2-3x/week guy ever tops. Every other day kind of schedule and this helped me get time to recover. I always had enough talent to be able to make progress on that type of schedule. And I never did it on vacation...everyone would ask me oh you went to brazil, how was the bjj and I would say that I didn't do any at all, ever. People thought I guess it should be more of an obsession and I should spar on vacation but I like to relax on vacation, not get beat up. Don't wreck yourself for the love of this, treat it as it is, something that benefits you, not masochism.
Flexibility was always my best asset and kept me away from a lot of injuries but also recognizing what was changing in my body and changing my game. Learning lower-risk guards and being able to keep people's weight off. Not getting tangled up, staying in shape, don't gain weight. As a smaller guy I could never succumb to the use of strength bc I was at a relative disadvantage on that. I used to power armbars from guard on men that outweighed me by more than 100lbs and were 10 years younger. At late 30s, that use of strength started to hurt me. At purple I started to really focus on sweeps, being on top, the traditional, sweep, pass, tap, position before submission approach. That really helped. It's harder to get hurt on top. And don't power through stuff.
And this is something that as an instructor I always try to emphasize- as you age, your own strength will cause you injuries if you apply it injudiciously. You've got to abandon the parts of your game that depend on huge power. If I force an armbar on someone now, I mess my lower back up. Have to start using better technique at some point in your evolution.
The other thing is learn good submission defense- by that I do not mean grab your belt harder to fight kimuras but rather recognize when a submission is a threat and learn to use posture and position and stay a step ahead of it. Don't get surprised by stuff, be hard to tap but not because you're willing to take risks, but because people can't get you locked down. Give ground when you need to and don't fight reality. Learn when you're in danger and take appropriate posture and positional steps immediately to get away from it. If someone is going for a kimura, I can't remember the last time I had to grab anything to fight it...I immediately yank my elbow down and recover it to the floor before they can solidify the position. So what if they get side control? Give ground and concede position where it keeps you safer from the submission.
I've also never been a footlock fan and don't really teach them much...I steer people clear of guillotines and also some stuff that I've had a couple students recently suffer identical collateral ligament injuries from, such as lasso guards. My advice to a lot of guys I've read through this whole thread is listen to your body better and train less.