So, a few days ago, I went to the student rec center on campus and swam until my arms felt like falling off (so, like, 10 minutes). For me, this is a rather strenuous workout.
Anyhow, a couple days later, and for a day or two after that, I noticed that every once in a while, when I moved my arms after sitting still for a while (for instance, donating blood plasma, an activity which does not lend one towards performing jumping jacks), I would feel my shoulder tighten up at some point within its normal range of motion, then a sharp (but not painful) pop as the tension released.
Any idea what causes this? It doesn’t bother me a lot, but I’m curious.
