Background and Aims
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. A limited amount of studies suggest an association between physical activity and CPM efficacy. However, these results await confirmation using objective physical activity measures. This study sought to determine the predictive relationship between physical activity and variation in CPM in 105 healthy adults. 

Methods
Physical activity levels were assessed during 7 days using the International Physical Activity Questionnaire and accelerometry. CPM was examined through a heterotopic noxious conditioning stimulation protocol which assessed the effect of a hot water conditioning stimulus on pressure pain thresholds. The predictive relationship between physical activity and CPM was explored using hierarchical regression analysis. 

Results
The CPM magnitude 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 ≥10.000 (= active) or ≥12.500 (= highly active) this significantly predicted more efficacious CPM.

Conclusions
As physical activity levels influence CPM efficacy, they should be taken into account as a confounding factor when examining CPM. 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 might have the capability to indirectly improve CPM and reduce or prevent pain.

DO PHYSICAL ACTIVITY LEVELS PREDICT THE EFFICACY OF CONDITIONED PAIN MODULATION? RESULTS FROM A CROSS-SECTIONAL STUDY IN HEALTHY INDIVIDUALS