Yesterday I was running a line on an astroturf pitch for University and by the end of the first half my lower back was in absolute knots and pain was radiating up through my shoulders as well. I will say that it was my second match of the day and my warm up in the first match was run abysmally by the referee so I didn't get in as good a stretch as I'd have liked to but I've still never experienced this kind of tightness, tension and pain in my lower back before. It got so bad that my concentration really suffered and I made a few mind-boggling decisions on goal kick/corner kick incidents. Any advice for lower back pain?