So I went and saw a doctor-type, and they told me that I had strained my extensors, including my glutes, on the left side of my body. This would explain why my ass hurts, too (and no, not in that way). He didn’t think I had done any skeletal damage, and that I should start stretching and doing light workouts as soon as possible.
The root cause seems to be a lack of stretching/warming up before playing Ultimate, compunded by a workout the day before. One of the exercises I had done was barbell lunges, which involves putting about a hundred pounds on your shoulders, and lunge-walking several reps of 10 steps. This exercise works your lower back and glutes quite nastily, and the odds are very good that those muscles were a lot tighter than normal on Saturday morning.
This is something I had pretty much figured out already, but it was nice to hear that the probability of skeletal injury was low. I have no pain radiating down my leg, and my right side is a-ok, so it’s most likely a strain/sprain, and not a herniated or slipped anything. Being able to say “I sprained my ass” is both funny and not.
In any case, I’m on the mend, and with stretching and exercise should be close to good as-new within a week. This means I’ll be good to go for hockey in a week and a half, which makes me very happy.
In case you were wondering, yes, I will be stretching the back and glutes in warm-up from now on. Sometimes I actually learn, the experience just has to be painful enough. This one definitely is up there on the pain-in-the-ass scale.