Patients in group 1 received a five-series Isometric Contraction of shoulder external rotators at 20% of maximal voluntary isometric contraction. Each series of Isometric Contraction was done until exhaustion or up to a maximum of 5 minutes. Patients received five sessions of treatment during a two-week period.

Patients in group 2 received a five-series Isometric Contraction of shoulder external rotators at 80% of maximal voluntary isometric contraction. Each series of Isometric Contraction was done until exhaustion or up to a maximum of 5 minutes. Patients received five sessions of treatment during a two-week period.

The intervention included the application of a series of isometric contraction for the external rotators shoulder muscles. The exercise protocol included two intensities; high-level isometric contraction (80% maximal voluntary isometric contraction) versus a low-level isometric contraction (20% maximal voluntary isometric contraction).

The Pain intensity Numerical Rating Scale is a self-reporting measure of pain intensity. This involves asking patients to rate their pain intensity by selecting a number on a horizontally depicted 11-point scale from 0 (no pain) to 10 (worst possible pain). Based on its several advantages (i.e. more responsive, sensitive and easy to administer) over other pain measuring scales, the PI-NRS has been recommended as a core outcome measure in clinical trials of chronic pain treatments. The minimal clinically important change for this scale has been reported to range from 1.5 to 3.2 points. Other authors have determined a meaningful clinical change of 2 points from baseline pain scores.

The shoulder function was assessed by the Constant Score scale. This is a multi-item functional scale assessing pain, activities of daily living, range of motion and strength of the affected shoulder. Its score ranges from 0 to 100 points, representing worst and best shoulder function respectively.

Pain and activities of daily living (subjective aspects receiving 35 points) are answered by the patient ; and range of motion and strength (objective aspects receiving 65 points) require a physical evaluation and are answered by the orthopaedic surgeon or the physiotherapist.