<qa>  What is the purpose of the study?Muscular stability is essential to the spinal column to avoid harmful strain and injury to its structures. Sudden postural disturbances impose reactive internal forces through the spine. If the muscles do not react before the internal reactive forces propagate through the spine, there is a short fraction of time where the spinal column may lack sufficient muscular support. Studies have shown that in patients with low back pain deep abdominal and back muscle have a delayed response to reactive forces. The purpose of this study is to verify these findings and to investigate whether tailored interventions can improve the reaction time in stabilizing muscle around the lower spinal column i patients with subacute and chronic low back pain. 