In the first part of the the study two new outcome measurements (force reproducibility and subacromial space) will be tested for reproducibility. Therefore 30 healthy people will be assessed.

In a second part of the study 60 patients will be randomly allocated to two groups. Group A (n=30) will perform a traditional training program and group B (n=30) will perform an eccentric training program.

Before the onset of the training programs, pain, function, maximal force, range of motion, subacromial space and force reproducibility will be assessed. Both training programs will be accomplished at home. The first six weeks there will be an appointment with the therapist once a week to explain, correct and when necessary, aggravate the exercises. The next six weeks these appointments will be diminished to once every two weeks.

After 6 and after 12 weeks of training the patients will be reassessed for all the parameters.

Inclusion Criteria:

• global tendon thinning
• inhomogeneous echo partitioning
• calcifications at the insertion
• symptoms present for at least 3 months: painful resisted isometric abduction, painful palpation of the supraspinatus tendon, impingement tests positive

Exclusion Criteria:

• documented full thickness rotator cuff rupture
• other lesions than CRCT at the moment of the study
• echographic criteria for ruptures (focal thinning, fluid-filled gap,compressibility)