I went to the house last night and at the exact same moment that I was pushing open the perpetually sticky front door, it opened from the inside, HARD. I hurled forward, just barely catching myself before I catapulted over my bike and into the front hallway. In doing so, I wrenched my back. I spent the rest of the evening in pain, flailing around in supine twists on the floor in front of the television in hopes of solving the problem (American Idol wasn't helping matters).
The pull was on the left side, I'm thinking it was the erector muscles along my spine that took the hit.
I went to sleep laying on my Acuball. The pain had diminished significantly by the morning, but I was still sore. Still, it's obviously nothing serious, just some muscle spasming. I took it easy in my practice today, particularly since I have a heavy teaching day ahead of me (4 classes).
I did the Suryas A and B, all the standing poses, then meandered off into my own hatha practice. I worked through most of my favourites: Supta Virasana, Supta Padangustashana, Eka Pada Raj Kapotanasana, did some restorative and Savasana. I used to do this all the time last year, when I didn't have time to get through the entire series. I would do either half-Primary or as-much-Primary-as-I-can-fit-in.
My back felt significantly better after the practice, so I'm pretty sure I'm on the mend, whatever it was.