Individuals with chronic shoulder pain have decreased muscle strength and range of motion, in addition to movement avoidance beliefs that may compromise functionality. Literature demonstrates a slight correlation between avoidance beliefs and shoulder dysfunction assessed through specific reliable questionnaires, but to our knowledge, no analysis has been performed with biomechanical parameters such as muscle strength with a gold standard equipment.

To analyze whether there is a correlation between muscle strength of external and internal rotators of the shoulder and avoidance behavior in individuals with chronic shoulder pain.

Forty-four individuals with chronic shoulder pain were evaluated (14 men and 30 women with a mean age of 46±11 years, BMI of 29±6 kg/m2 and pain intensity of 5±3 on the Visual Analog Scale). Those over 55 years old, with difficulties in understanding the questionnaires, previous surgery and fracture, presence of tumor and neurological disorders were excluded. The Visual Analogue Scale (0-10) was applied to assess pain intensity. The Avoidance Daily Activities Photo (ADAP) Shoulder Scale was applied to analyze movement avoidance behavior. ADAP has three domains: free movement, effort and self-care. Then, the individuals were seated on the isokinetic dynamometer (Biodex 4). Muscle strength of external and internal rotators of the shoulder was assessed using three concentric isokinetic contractions with verbal feedback for encouragement. A warm-up test was previously performed with three submaximal contractions. Stabilization was performed using belts in the pelvic and thoracic region. The arm position was 45° of elevation in the scapular plane and 90° of elbow flexion, complete range of motion of 60° (30° of internal rotation and 30° of external rotation) with a speed of 60°/s.

Spearman's correlation analysis resulted in a weak negative correlation between muscle strength in external rotation and the ADAP Effort domain (rho=-0.3; p= 0.014) and between muscle strength in internal rotation and the ADAP Effort domain (rho=-0.3; p=0.042).

There is a weak negative correlation between shoulder rotator muscle strength and the ADAP effort domain scale, thus, people with chronic shoulder pain who have less strength demonstrate greater avoidance behavior in relation to effort activities.

This study showed that individuals with chronic shoulder pain and decreased muscle strength of shoulder rotators may exhibit movement avoidance behavior. It is important for the clinician to assess these determinants to propose a treatment that includes muscle strength and exposure strategies to movements that involve effort in individuals with chronic shoulder pain.