Pre-Exercise Conditioned Pain Modulation Is Associated With Exercise-Induced Hypoalgesia in Patients With Painful Rotator Cuff Tears.

BACKGROUND

Exercise-induced hypoalgesia (EIH) is a well-established phenomenon; however, its magnitude varies among individuals and clinical conditions. In patients with rotator cuff tear (RCT), movement-evoked pain during arm elevation is a key symptom directly linked to functional limitations, making EIH particularly clinically relevant. This study aimed to investigate whether pre-exercise endogenous pain inhibitory capacity, assessed using conditioned pain modulation (CPM), is associated with EIH magnitude in patients with painful RCT.

METHODS

Thirty patients with symptomatic RCT performed 25 min of moderate-intensity stationary cycling. Movement-evoked pain during active shoulder flexion and pressure pain thresholds at the affected deltoid, contralateral deltoid and contralateral tibialis anterior were assessed before and immediately after exercise. CPM was evaluated using cuff algometry before the intervention.

RESULTS

A significant reduction in movement-evoked pain was observed following exercise (median reduction: 21.0 [9.0-35.0] mm, p < 0.001, r = 0.83), accompanied by increased PPTs at all sites (p < 0.05). A moderate correlation was observed between CPM efficiency and post-exercise pain reduction (ρ = 0.56, p = 0.002). ROC analysis identified a CPM cutoff value of 4.05 kPa for detecting EIH responders (AUC = 0.917).

CONCLUSIONS

Clinically meaningful reductions in movement-evoked pain were observed following moderate-intensity aerobic exercise in patients with painful rotator cuff tears. Greater pre-exercise CPM efficiency was associated with greater post-exercise pain reduction, suggesting that endogenous pain inhibitory function may contribute to inter-individual variability in the immediate pain response following exercise.

SIGNIFICANCE STATEMENT: This study demonstrates that pre-exercise conditioned pain modulation (CPM) is associated with the magnitude of exercise-induced hypoalgesia in patients with rotator cuff tear. Unlike previous studies focusing primarily on experimental pain sensitivity, we demonstrated clinically meaningful reductions in movement-evoked pain together with widespread increases in pressure pain thresholds. These findings identify pre-exercise CPM as a potential marker of individual variability in the immediate analgesic response to exercise and provide a basis for future mechanism-based stratification of exercise interventions.