KB Swings, Toes to bar, Thrusters, SDLHP's, Prowler Push

4 Rounds for time of:
20 KB Swings @ 45lbs
20 Toes to bar
2.  Thrusters
20 SDLHP's @ 45lbs
2.  Prowler Pushes - down and back x 2
2 min rest
Splits
1 - 3:06
2 - 3:30
3 - 4:06
4 - 4:34
Total time w/ rest - 21:17

It was hard but I was enjoying this one until round 3.  I felt a twinge mid back in thrusters then on the SDLHP my pelvis shifted on rep 6 or 8 and I felt my low back start to seize up.  I finished the round and the last but skipped the thrusters last round.  I also slowed way down.  I can only guess that the thruster weakened me and then I got loose in my core.  This sucks.  I have been doing tons better with my back over the last few weeks.  I can't miss any workouts with this.  I am going to hang a bunch today and hope for the best.