Daily physical activity levels are predictive of the effectiveness of conditioned pain modulation

Whereas literature on the association between physical activity and pain sensitivity is well depicted, research into the association between physical activity and conditioned pain modulation (CPM) is less extensive. Previous research has demonstrated that individual differences in the efficacy of CPM among healthy persons can be accounted for by personal factors.1 A limited amount of studies also suggest that physical activity may be associated with CPM efficacy. However, these results await confirmation using objective physical activity measures. In this cross-sectional study, during 7 days prior to CPM assessment, physical activity levels of 15 healthy adults were registered through continuous accelerometry and self-report using the validated International Physical Activity Questionnaire. CPM was evaluated using a standardized heterotopic noxious conditioning stimulation (HNCS) protocol during which the influence of a noxious conditioning stimulus on a noxious test stimulus was assessed. Before, during, and after immersion of the non-dominant hand into hot water (i.e. conditioning stimulus) pressure pain thresholds (i.e. test stimulus) were evaluated at the dominant hand, neck, and leg. Hierarchical regression was conducted to determine a predictive relationship between physical activity and CPM efficacy, meanwhile controlling for potential confounders of experimental pain testing. The HNCS protocol was effective in eliciting a CPM response. The magnitude of this CPM response was positively correlated with the physical activity levels. Higher self-reported levels of moderate physical activity (e.g. cycling <16km/h) significantly predicted greater CPM magnitude. When the number per steps per day, as registered with accelerometry, was ≥1. (= active) or ≥12.5 (= highly active) this significantly predicted more efficacious CPM. These findings highlight the importance of physical activity in enhancing inhibitory endogenous pain modulation. Additionally, physical activity might be useful in the treatment of chronic pain patients in whom dysfunctional CPM is established. Performing activities of moderate intensity and walking are achievable for such patients and can be implemented in activity management programs to indirectly improve CPM and reduce or prevent pain. Process evaluation: Replication of hierarchical regression analysis in analogy to previous studies was challenging due to unclear descriptions.