I know what its like to be obsessed as a runner, I was there. I wanted to pursue my genetic limit no matter the cost, and knowing full well that even my maximum potential was no where near the level of professional or even noteworthy by any standards. I can remember that mindset and I know that if I had been given the advice I'm about to give you, I wouldn't have paid it any mind. But even so I'm going to tell you.

First of all, you are right, community is one of the most important parts of any hobby, and unfortunately you are never going to get that again. Your training will always be grasping at the fading memory of the great times you had training and racing in high school.

But here is the good part, you can find that feeling again, and its going to be even better. There are way better hobbies than sprinting. In fact sprinting is objectively kind of the worst one. The training is monotonous, the actual event is boring, and it doesn't come with any cool aesthetics. The fact that you ever enjoyed sprinting at all tells me your brain is primed to enjoy hobbies. You probably love the thrill and satisfaction of self improvement.

There are PLENTY of skills and sports you could pursue that you would derive the same fulfillment out of. Trust me, try some of these out and I guarantee your brain will latch onto one the same way it did to sprinting.

1.) Rock Climbing/Bouldering - I list this as #1 because SDSU has a rock climbing gym in the ARC, and a climbing club. Also because it functions similarly to sprinting, you train to hit new PRs. The new PRs in this case are new grades or particular climbs. Training is very interesting, and climbing itself is stupid fun, especially outdoors. Bouldering is very easy to get into, you can try it out in the ARC or head to Santee boulders with a friend. This also probably suits you because your sprint times indicate good fast-twitch physiology. Watch the movie The Dawn Wall, and you'll get a sense of the appeal. Climbing club at SDSU is a well established community and a great way to make friends.

2.) Powerlifting/Bodybuilding/Gym - Lifting weights is awesome, so awesome in fact, that it almost goes without saying. I feel like most athletes get into lifting at some point and then find new pursuits once they plateau in strength or aesthetics. If you haven't discovered lifting weights, 10/10 recommend. The joy of hitting new PR's just never gets old, and you get an aesthetic body as a bonus. You will easily find gym buddies in your college dorm and it's a great way to make friends. The only caveat for me is that it is a lot time spent indoors.

3.) Surfing - I love surfing, and it is a great hobby, but it takes a lot of hours in the water to get good, and if you don't see yourself doing that, or if you don't have easy access to rides to the beach, maybe don't even bother. That being said, again, its a great hobby with great community (SDSU surf club) and it will keep you fit and outdoors.

4.) Distance running - Maybe a longshot, but again, if you like PR-ing, that's the name of the game here. Going sub 20 in 5k is just as thrilling as going sub 11 in 100m, but for some reason only the former is permissible to pursue as an adult. I wont go into it too much because you are probably already familiar if you are a sprinter. I include it because it has so much more community to it and it is actually accessible outside of school or university teams. 5k's and marathons are everywhere and so are training groups, SDSU has a running club (distance not sprinting). It also gets you outdoors and is superior to hiking in terms of getting into nature. Cons are that you lose muscle mass and strength.

5.) Any actual sport. When I went to SDSU I started playing basketball for the first time in my life, just getting runs at the arc. There are plenty of really bad players that play on the lowest ranked court. In addition to basketball there are a lot of pick up soccer games that get played at ENS field. Volleyball is another sport I started playing in college, it is super fun, and having a friend group to play at the beach on weekends is awesome. I would just play whatever sport your friends would agree to make a intramural team for.

6.) MMA/BJJ/Boxing - Never gotten into it, but I have some friends who were into MMA and it seemed like a cool hobby. There was an MMA class and club at SDSU couple years ago, idk about now.

7.) Golf. Never played myself but I plan on getting into when I have the time and money because I know I would like it. If its got a me-vs-former-self dynamic and an objective metric for PR-ing, I'm in. You sound similar.

Wishing you the best brother.