The Flares of Low back pain with Activity Research Study (FLAReS): study protocol for a case-crossover study nested within a cohort study oleh Pradeep Suri, Adrienne D. Tanus, Nikki Torres, Andrew Timmons, Bianca Irimia, Janna L. Friedly, Anna Korpak, Clinton Daniels, Daniel Morelli, Paul W. Hodges, Nathalia Costa, Melissa A. Day, Patrick J. Heagerty, Mark P. Jensen