This was a single-blinded, randomized parallel study. Eighty-two patients presenting chronic musculoskeletal shoulder pain were allocated to two groups. Patients in group 1 (n= 41) received a five-series Isometric Contraction of shoulder external rotators at 20% maximal voluntary isometric contraction, while patients in group 2 (n= 41) received similar protocol but the intensity of contraction was set at 80% maximal voluntary isometric contraction. In both cases, each series of IC was done until exhaustion or up to a maximum of 5 minutes. Patients received five sessions of treatment during a two-week period. Outcome measures included muscle pain sensitivity (pressure pain thresholds) and pain intensity (pain intensity numerical rating score), and shoulder function (Constant Score).
