Effect of Isometric Exercise on Pain Perception in Rotator Cuff Related Shoulder Pain

The aim of this study is to compare the immediate effects of an acute bout of isometric exercise of the shoulder external rotator muscles above and below pain threshold on pain intensity, pain threshold, conditioned pain modulation and pain free force in external rotation.

It will consist of a randomized three-treatment parallel-design study. The sample will consist of subjects with rotator cuff related shoulder pain (RCRSP). Once the sample is selected, subjects will participate in three experimental sessions, which will occur in a randomized order: two exercise sessions (supra-threshold and infra-threshold isometric exercise) and one control session. In the first session, information regarding clinical and demographical aspects will be collected. A washout period of approximately 48 hours will separate each of the experimental sessions.

To evaluate the results of the exercise, the subjects will be assessed at pre-intervention, immediately post-intervention and 45 minutes after each experimental condition. Pain intensity, Pressure Pain Thresholds (PPT), Conditioned Pain Modulation (CPM), maximal voluntary isometric contraction (MVIC) and pain free isometric strength (PFIS) will be measured.

Inclusion criteria

• aged 18-80 years (likelihood of patients > 80 having degenerative changes in the shoulder is increased)
• pain localised to the proximal anterolateral shoulder region
• positive for pain on at least one of the following three impingement tests: Hawkins-Kennedy, Neer's, Jobe's
• positive for pain on resisted external rotation and/or abduction.

Exclusion criteria

• shoulder surgery within last 6 months
• reasons to suspect systemic pathology including inflammatory disorders, cervical repeated movement testing affects shoulder pain and/or range of movement, passive external rotation deficit greater (less than 30º or a range of motion reduction of 50% or more as compared to the contralateral side), upper limb tension test A for cervical radiculopathy
• atraumatic degenerative rotator cuff tear based on the cluster of clinical tests (painful arc, drop arm test, and marked weakness into ER all three positive)