I honestly don't know exactly how it happened, I didn't feel anything until a while after my workout the other night - no pull, no pop, not even a twinge but about an our after my indian club workout a few days back I felt a deep ache at the base of my thumb. At first I didn't think a whole lot of it, but it hasn't really shown much sign of improvement - it's pretty much holding me up from doing any serious strength work involving my left hand.
Sooooo, my workouts have been focused on the conditioning side for the last few days. I've been doing stair sprints, plyos, hill sprints, high rep bodyweight squats and chair squats - my quads are suffering, but in a good way.
I've waded my way through about half of Born to Run in the little free time I get at night after the kids are in bed, and so far it just keeps getting better and better.