Neurophysiology of Weakness and Exercise in Rotator Cuff Tendinopathy

Neurophysiology of Weakness and Exercise in Rotator Cuff Tendinopathy

The purpose of this study is to examine deficits in activation and motor patterns, as well as central drive in patients with rotator cuff tendinopathy. There are three specific aims: (1) determine the effect of acute pain relief on rotator cuff muscle activation in patients with rotator cuff tendinopathy, (2) determine the effect of exercise on rotator cuff muscle activation in patients with rotator cuff tendinopathy, and (3) compare rotator cuff muscle activation between patients with rotator cuff tendinopathy and healthy controls.

The long-term goal of our research agenda is to identify the mechanisms associated with rotator cuff tendinopathy (impingement syndrome) and subsequently evaluate novel treatment strategies that address these mechanisms. The objectives of this application are to study the muscle patterns in patients with rotator cuff tendinopathy as well as the effects of both pain and exercise on these patterns. Our first hypothesis is that pain relief from a shoulder injection will result in increased rotator cuff activity. Our second hypothesis is that patients with tendinopathy will demonstrate improved rotator cuff muscle activity following a six-week exercise program and that this improvement will be higher in patients that respond favorably to treatment. Our final hypothesis is that patients with cuff tendinopathy will show decreased rotator cuff activity compared to healthy subjects. The investigators plan on addressing these hypotheses using several novel techniques for muscle activity assessment.

Patient Inclusion Criteria:

• pain with passive provocative maneuvers (positive Hawkins or Neer test)
• pain with active elevation (positive painful arc)
• pain with isometric resisted movements (Jobe's "empty can" test or resisted shoulder external rotation with the arm at the side)
• demonstrate weakness (>10% force deficit in external rotation)

Patient Exclusion Criteria:

• shoulder surgery on the symptomatic side
• positive Spurling test
• traumatic shoulder dislocation or instability in the past 3 months
• reproduction of shoulder pain with active or passive cervical range of motion
• signs of rotator cuff tear (drop-arm test, lag signs, gross external rotation weakness, or positive image findings)
• current musculoskeletal, neurologic or cardiovascular compromise

Control Inclusion Criteria:

• no current or previous shoulder injury
• matched for age (within 5 years) and sex
• meet Patient Exclusion Criteria (minus musculoskeletal, neurologic, or cardiovascular compromise)

Control Exclusion Criteria:

• pain with active arm elevation
• positive Hawkins, Neer, or Jobe's test