The influence of exercise on clinical pain and pain mechanisms in patients with subacromial pain syndrome

This study examined if 8-weeks of exercise could modulate central pain mechanisms in patients with subacromial pain syndrome (SAPS), and if the effect of exercise could be predicted from these parameters.

Thirty-seven patients completed a progressive abduction exercise program every other day for 8-weeks. Worst shoulder pain in full abduction was rated on a Numeric Rating Scale (NRS). Pain pressure thresholds (PPTs), temporal summation of pain (TSP), conditioned pain modulation (CPM), exercise-induced hypoalgesia (EIH), Shoulder Pain and Disability Index (SPADI), Pain Catastrophizing Scale (PCS), PainDETECT questionnaire (PD-Q), Pain Self-Efficacy Questionnaire (PSE-Q) and Pittsburgh Sleep Quality Index (PSQI) were assessed before and after intervention.

The intervention improved worst pain intensity (P<0.001), boosted the CPM (P<0.001), improved the sleep scores (P<0.005) and reduced the PainDETECT ratings (P<0.001). No changes were observed in PPT, TSP, EIH, SPADI, PCS and PSE-Q (all P>0.05). In a linear regression, the combination of all baseline parameters predicted 23.2% variance in absolute change in pain after 8 weeks. Applying backwards elimination to the linear regression yielded that baseline pain intensity combined with TSP predicted 33.8% variance.

This explorative study suggested reduction in pain, improved sleep quality and increased CPM after 8-weeks of exercise. Furthermore, the results suggests that low pain intensity and high TSP scores (indicative for pain sensitisation) may predict a lack of pain improvement after exercise.

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Steen Lund Jensen