CrossFlowX™: Lower Back Solution Mid Length. 43 minutes. Did you know that low back pain is a significant cause of missed workdays, with a substantial portion of working adults reporting absences due to back pain, according to several studies? Over 4 million adults report difficulties with employment due to back pain. The impact is particularly severe in working-age populations, where low back pain is a leading cause of disability. This video is the first of three that I will release that aim to help relieve lower back pain and discomfort. This CFX version is full length. There will be a CFV version of this next, and there already is a longer CFX.