The influence of aerobic exercise on conditioned pain modulation and manipulation induced analgesia in people with lateral epicondylalgia: a randomised controlled trial

Abstract Background: Exercise has been shown to reduce pain sensitivity. It is unclear whether exercise can also potentiate the endogenous analgesia and reduction in pain sensitivity produced by conditioned pain modulation (CPM) and manipulation induced analgesia (MIA).Objectives: To determine whether aerobic exercise potentiates CPM and MIA and to investigate associations between exercise induced analgesia, CPM and MIA.Design: Parallel randomised, controlled trial using computer-generated randomisation to allocate interventions. Methods: A gender-stratified convenience sample included 68 participants with lateral epicondylalgia (LE) from Perth, Western Australia, recruited between October 2017 and June 2018. Participants were allocated to receive either moderate intensity aerobic exercise (control condition, n=34) or high intensity aerobic exercise (active condition, n=34) for 15 minutes on two separate test sessions, with a three-day rest in between. Exercise intensity was determined based on age-related target heart rate (HR) corresponding to 50% and 75% of maximum HR respectively. Following aerobic exercise, participants were immediately assessed for CPM or MIA response, one on each test day, in a random order. A blinded assessor measured pressure pain thresholds (PPT), the main outcome measure, at the elbow and ipsilateral wrist to evaluate CPM and MIA. Data were analysed using linear mixed models, partial correlations, and univariate regression. Results: All participants showed significant increases in PPT at both test sites (p<0.001). The high intensity exercise group demonstrated higher levels of CPM and MIA at both test sites (p<0.001). There were large and positive partial correlations between CPM/MIA and the initial change in PPT following exercise (CPM (r:0.90–0.93, p<0.001)/MIA (r:0.68–0.86, p<0.001)). The change in PPT following aerobic exercise was a significant predictor of both CPM (adjusted R2:92%-95%) and MIA (adjusted R2:73%-93%) response. Conclusion: An acute bout of high intensity aerobic exercise significantly enhanced the analgesic effect of CPM and MIA in people with LE. CPM and MIA may activate similar descending inhibitory mechanisms to mediate their analgesic effects.Trial registration: Prospectively registered with the Australia New Zealand Clinical Trials Registry on 9/02/2017: ACTRN12617000219381, https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=372232