Chronic low back pain (CLBP) is one of the most prevalent musculoskeletal disorders and a major contributor to disability worldwide. Exercise is recommended in guidelines as a cornerstone of the management of CLBP. One of the manifold benefits of exercise is its influence on endogenous pain modulation. An acute bout of exercise elicits a temporary decrease in pain sensitivity, described as exercise-induced hypoalgesia (EIH). This thesis explores EIH in people with CLBP via a systematic review and observational studies.
The systematic review included 17 studies in people with spinal pain. Of those, four studies considered people with CLBP revealing very low quality evidence with conflicting results. EIH was elicited following remote cycling tasks (two studies, fair risk of bias), but EIH was altered following local repetitive lifting tasks (two studies, good/fair risk of bias).
The observational studies investigated EIH following three different tasks in participants with and without CLBP and explored the stability of EIH results. Conflicting results from quantitative sensory testing were found for whether EIH is impaired in people with CLBP. EIH was only elicited in asymptomatic participants following a repeated lifting task, but both participants with and without CLBP showed EIH following a lumbar resistance and a brisk walking task. This thesis demonstrates the first evidence of stability of EIH over multiple sessions. However, the interpretation of the results can be challenging as stability was poor and changes in lumbar pressure pain thresholds also occurred after rest only.
These findings are important to inform future studies contributing to the elucidation of the complex phenomenon of EIH in people with/without CLBP, specifically as the stability is a prerequisite for future research
