Rotator cuff tendinopathy (RCT) is regarded as a common and burdensome source of shoulder pain with prevalence estimated to be as high as 14% in general working-age population. RCT is a broad entity, including a vast variety of diagnosis such as shoulder impingement syndrome, RC tendinitis/tendinosis, as well as subacromial bursitis. The course of RCT is characterised by persistent pain and/or disability and/or recurrent episodes. It often leads to decrease function, lower health-related quality of life, poor sleep quality, work absenteeism, as well as patient's suffering. Previous studies support exercise as an adequate treatment in RCT. Nevertheless, our knowledge, there is no studies evaluating the effects of isoinertial training in RCT. Therefore, the aim of this study will be to pilot the methods proposed to conduct a substantive study to evaluate the efficacy of isoinertial training plus eccentric training versus eccentric training alone on improving pain and function in RCT. The objectives were to evaluate: (i) The process of recruitment and retention rates; (ii) Willingness of participants to be randomised; (iii) The extent of contamination between groups; (iv) Participant adherence with treatment. The secondary aim will be to analyse the effects of isoinertial training plus eccentric training versus eccentric training alone on rotator cuff strength, scapular muscle activity, and scapular muscle endurance in people with RCT.

Study design and setting The design of the present study will be a randomized controlled single-blind trial with 2 follow-ups (one week and one month after intervention) that will be performed between January 2017 and March 2017 in one private physiotherapy clinic in Malaga, Spain. The outcomes will be assessed at baseline (t1), one week after intervention (t2), and one month after intervention (t3). Written informed consent will be acquired for all participants prior to their participation. The study will be implemented and reported in line with the CONSORT statement.

Recruitment Eligible participants who will be interested in the study will be asked to provide written informed consent to participate. Subsequently the patient-reported outcome measures will be completed to establish baseline pain, function, rotator cuff strength, scapular muscle activity, scapular muscle endurance and level of self-efficacy. After completion of the baseline measures, the participants will be randomly allocated to the isoinertial training plus eccentric or eccentric training groups. The measures of pain, function, rotator cuff strength, scapular muscle activity, scapular muscle endurance and self-efficacy will be repeated one week and one month after intervention. Anonymized age and gender will be collected for those participants who decline to take part in the study to assess the external validity of the recruited sample of participants. Participant data files will be stored in numerical order and in a secure and accessible place and manner. Participant files will be maintained in storage for a period of 3 years after completion of the study.

Inclusion Criteria:

• Age between 18-35 years
• Willing and able to participate
• Primary complaint of shoulder pain
• No/minimal resting for shoulder pain
• Range of shoulder movement largely preserved
• Two out of three positive impingement tests: empty-can test, Hawkins-Kennedy test, modified Neer test
• Pain on isometric rotator cuff testing, usually abduction or lateral rotation.

Exclusion Criteria:

• Subjective feeling of instability and positive apprehension sign
• Positive scapular assistance and/or resistance test
• Partial or full ruptures of the rotator cuff
• Calcifications greater than 4 mm
• (Acromion type III (per Bigliani criteria)
• Bursitis
• History of shoulder fracture and/or shoulder surgery
• Glenohumeral disorders (inflammatory arthritis, osteoarthritis, osteonecrosis, cuff arthropathy, septic arthritis, adhesive capsulitis, glenohumeral instability); (viii) Regional disorders (cervical radiculopathy, brachial neuritis, nerve entrapment syndrome, sternoclavicular arthritis, reflex sympathetic dystrophy, and neoplasms)
• Systemic diseases
• Corticosteroid injection 3 months prior to the study treatment and within 1 months prior to the study treatment on other body parts.