AP, i have had pretty regular back pain over the past year or two since i starting lifting. i went to PT to see if they could do anything and all they recommended was stretching, specifically your hamstrings. evidently short/tight hamstrings cause you to overcompensate with lower back muscles and can cause acute achy pain as a result. i didn't buy it at first, but since i have started stretching my back feels a ton better. i usually stretch before and after a WOD if i have time, and sometimes at night before bed. it will take a few weeks before you start to notice a difference, but hopefully it helps.