Yesterday I tried something I hadn't done for a while, Functional Strength, which is one of Tracey Long's workouts and several years old. It was fine but I felt a little blah after around 30 minutes, so then I did some biceps and tricep dips/pushups on my own and then put in Cathe's CCC and did round one then sort of did round two, then some ab stuff on my own and a stretch.
Anyway, I'm not sure exactly when/how, but I tweaked something in my back, a little below the middle on the left side. Does not feel good. I went to yoga class today anyway, though. The yoga didn't bother it, although there ended up being a couple things I couldn't quite do. Tomorrow is definitely a rest day.