The purpose of this study is to compare two different physical therapy exercise programs in persons who have shoulder pain in order to determine if they have a different affect on pain level and ability to use the injured shoulder after treatment. Both exercise groups will attend physical therapy for an hour,two to three times a week, for eight weeks. The first two weeks of therapy sessions will involve learning the exercises and testing to determine what weight to use during exercises. One group will perform a traditional therapy exercise program for shoulders using hand weights. The other group will perform a version of the same shoulder exercises but with a different exercise technique. Exercises in both programs are part of the standard of care for shoulder impingement in physical therapy but one program concentrates on the lowering portion of the exercise (eccentrics) while the other emphasizes the lifting portion of the exercise (concentrics). Both groups will perform the same warm-up, stretching, and cool-down exercises. Participants will also be required to perform a daily home exercise program of stretches and range of motion that will take about 20 minutes to complete. Exercise testing will determine the hand weight resistance used by each person during their therapy sessions and re-testing will occur every two weeks to determine any changes in the weight used for the exercises to keep them challenging. Pain level, ability to use the injured arm for daily activities, strength, and amount of movement in the shoulder, will be measured at the start of physical therapy and after five and eight weeks (end of study) of the exercise treatments. A concurrent study investigating the reliability of the shoulder motion and strength measurements used in the larger study will also be performed.

Research hypotheses:

1. Adults with shoulder pain who complete the eccentric progressive resistive exercise intervention will demonstrate significantly greater improvements in the outcome measures at three weeks, earlier in the intervention, than the concentric progressive resistive exercise intervention group.
2. Adults with shoulder pain who perform progressive resistive exercise interventions, regardless of contraction type, will demonstrate significant improvement in the shoulder outcome measures at three and six weeks of intervention.

This study will be a prospective, repeated-measure, randomized clinical trial comparing shoulder outcome measures in adults with SAIS following eccentric or concentric progressive resistance exercise intervention programs. Subjects: 36 persons with SAIS, aged 18 and older, will be recruited from the Texas Health Resources Dallas outpatient rehabilitation department and referring physicians. Procedures: Participants will be randomly assigned to either a concentric or eccentric intervention group. Participants will complete outcome measures for pain intensity, shoulder function, shoulder pain-free active range of motion (AROM) of flexion and scapular plane elevation, and shoulder pain-free strength of external rotation and abduction. Outcomes will be assessed by an investigator blinded to group assignment at baseline and after three and six weeks of intervention. Interventions will consist of supervised exercise sessions three times a week. Exercise progression will follow a standardized and systematic approach. The reliability of the AROM and strength outcome measures will be assessed concurrently using a random subset of six participants from each group.

Inclusion Criteria:

• 18 years of age and older
• Present with clinical signs of subacromial impingement syndrome
• Have not yet initiated physical or occupational therapy treatment

Exclusion Criteria:

• Previous shoulder, cervical, or thoracic surgery.
• History of shoulder fracture, dislocation, labral tear, or full thickness rotator cuff tear
• Treatment for neoplasm in the last year
• Rheumatic disease
• Adhesive capsulitis
• Shoulder pain currently rated greater than or equal to 8/10 on the NPRS
• Cardiac, neurological, or musculoskeletal condition that precludes ability to perform upper extremity resisted exercise
• Pregnancy
• inability to understand spoken or written English
• Inability to arrange transport to evaluation or treatment sessions or not planning to stay in the area long enough to complete study