Endogenous pain modulation (EPM) changes after a course of exercise therapy in low back pain (LBP): A pilot feasibility study

Objectives: A significant driver of low back pain (LBP) is adaptations to endogenous pain modulation (EPM). Exercise modulates pain through various mechanisms, however, there is a lack of information on its relation to EPM. The objective of this study was to evaluate the feasibility of a protocol investigating if changes in EPM occurs after exercise therapy. Methods: Participants were recruited from an ongoing randomized controlled trial comparing graded activity to motor control exercises. Participants attended 2 in person sessions pre and post intervention to assess pain pressure threshold (PPT), temporal summation (TS), conditioned pain modulation (CPM) and exercise induced hypoalgesia (EIH). Feasibility outcomes included attrition, recruitment rate, exercise adherence, protocol burden and consistency. In total, 36 (53%) eligible participants enrolled and completed baseline assessments. Results: A-priori thresholds for feasibility were met for attrition 32/36 (89%), recruitment rate (53% of eligible participant enrolled and 36 recruited in 6 months), exercise adherence (93.8%) and satisfaction with assessment protocols (bothersome 88.9%, future participation 97.2%), apart from discomfort with assessment (58.3%). Participants reported that the CPM caused the most discomfort. There was a trend for an increase in low back PPT, no change in TS, and a decrease in CPM and thumbnail PPT at follow up. The results demonstrated that the protocol is feasible for all pre-specified outcomes. Discussion: This article presents a protocol for EPM using PPT, TS, CPM and EIH that is feasible in a clinical trial for LBP. A future study is needed to further investigate EPM changes after exercise therapy in this population.