The study was designed as a prospective, randomized single-blind trial with an intervention period of 12 weeks. Patients were recruited from the outpatient clinic at the Department of Physical Medicine and Rehabilitation, Oslo University Hospital, Oslo, Norway. During a regular consultation for shoulder pain, the physicians at the outpatient clinic evaluated eligibility for all patients examined. Patients with SAPS lasting at least three months were eligible. The patients then were referred to a medical student for inclusion of the trial.
The inclusion criteria were pain on one of two isometric tests (abduction or external rotation); positive Hawkins-Kennedy impingement sign; and normal passive glenohumeral range of motion. The exclusion criteria were previous surgery on the affected shoulder; instability; rheumatoid arthritis; clinically considered full thickness tear of the rotator cuff; clinical signs of nerve root symptoms from the neck; patients considered unable to fill out questionnaires in Norwegian or follow the treatment; pregnancy; and injection of cortisone in the affected shoulder in the last six weeks.
The study was approved in the Regional committee for medical and health research ethics (REK) ref: 2017/1277 and was registered in the ClinicalTrials.gov: NCT03317808. The study adheres to the Consort guidelines. All study participants have submitted written approval for participation in the study.
The patients were randomized to one of two different intervention groups (HSR and traditional treatment) by a pc-based block randomization with four in each block. The allocation ratio was 1:1. A research assistant not involved in any other part of the study opened the sealed opaque envelopes and assigned the patients to their respective treatment group. The outcome assessors were masked to treatment allocation. Subjects with bilateral symptoms received treatment for both shoulders, but only the most painful shoulder at baseline was selected for analysis. The patients were informed that they could not receive any other form for physical therapy during this period, but they were allowed to use analgesics.
Heavy slow resistance
The patients in the heavy slow resistance group received one training session each week for 12 weeks supervised by the physical therapist at Oslo University Hospital. They were also instructed to exercise two sessions weekly at home. Each session consisted of exercise for shoulder flexion, abduction and external rotation. Flexion was performed in supine position, whereas abduction and external rotation were performed in side-lying position. All exercises were performed in both in eccentric and concentric phase. Patients were also instructed in different stretching exercises if needed. For the first three weeks of training, they were given soft tissue treatment in addition. During the 12 weeks the treatment lasted, the number of repetitions gradually decreased, and the load gradually increased. Some pain during, and after, exercise was acceptable, but if the pain lasted to the next day, the load was decreased. The load also decreased if the pain during the exercise exceeded a threshold of 5 on an 11-pointed pain (0–10) Numeric Rating Scale (NRS). To improve compliance the patients were given a training diary to register the number of the training session they completed for each week, and what load they used.
The patients in the heavy slow resistance group were also informed about the possibility to transfer to the other group, if the treatment was considered ineffective or the pain increased.
Traditional supervised exercises
The patients in the traditional group were given treatment by a physical therapist, conducted one-to-one, twice a week for 12 weeks, in addition to daily home-exercises. This is a program developed by at Ullevål University Hospital (now Oslo University Hospital) in the 1980s13, with a documented effect in earlier studies14, 15, 16.
The following paragraph is a description of the training regimen by the developer Bøhmer14 “The first session included gathering of medical history as well as bilateral inspection of alignment, including scapula and the glenohumeral joint. Movement pattern, the immediate co-contraction, and timing of the scapula and the arm were observed during elevation to obtain a functional diagnosis for individual guidance of treatment. The principal treatment focus was on relearning of normal movement patterns, which could then be transferred to daily activities. The initial aim was to unload the stress on the rotator cuff and subacromial structures. This phase entailed awareness of posture and the use of manual techniques for tense muscles, and elastic rubber band for relaxed repetitive movements, exercises for periscapular muscles, and a vertically fixed sling. The focus in the next phase was to increase the eccentric force when the patient was lowering the arm in standing position. The patients received immediate feedback from and correction by the physical therapist. Subsequently, endurance exercises with gradually increasing resistance were performed.”
The primary outcome was change in the Shoulder Pain and Disability Index (SPADI) score17. The SPADI score is a self-report questionnaire with twelve questions regarding the last week divided into two dimensions: five questions for pain and eight questions for disability of the shoulder. Each dimension accounts for 50% of the overall score. The questions are answered by marking on a visual analogue scale, which are later converted to scores from 0 to 10. 0 = no pain/problem, 10 = worst possible pain/so difficult I needed help. The questionnaire is concluded to be reliable and acceptable for assessing Norwegian-speaking patients with subacromial shoulder pain, with 19.7 being the smallest detectable change (SDC)18.
Secondary outcomes were the Disabilities of the Arm, Shoulder and Hand (DASH) score19, pain in activity and rest last week and shoulder function last week. DASH is also a self-report questionnaire that contains of 30 questions regarding dysfunction of the shoulder the last week, five work-related questions and five sport- and instrument-related questions. DASH is previously evaluated, SDC reported at 11.8, and is recommended to measure outcome in patients with shoulder pain in Norway20.
Pain on activity and at rest last week and shoulder function last week were all measured on an 11 point Likert-type scale: 0 = no pain/problem, 10 = worst possible pain/impossible to complete. Answers were converted in the same way as the SPADI questions. Besides, the shoulder function was evaluated with two questions: “Can you carry a 5 kg shopping bag” and “Can you take something down from a high shelf?”
Outcomes were evaluated at baseline and at the end of the 12-week intervention.The patients completed a written questionnaire and underwent a physical examination at both time points. The baseline questionnaire was however, more comprehensive and included sociodemographic and clinical factors such as sex, age, marital status, education, work and sick leave, duration of symptoms, self-efficacy and outcome expectations.
This study is a pilot study; therefore a calculation of sample size was not performed. IBM SPSS version 25 was used for all statistical analyses. A medical student completed the clinical evaluation and to avoid bias, this person was blinded during the study and the analyses. Terms used and given in the results are mean, standard deviation (SD), numbers, percentages, odds ratio (OR) and 95% confidence intervals (CI).
The analyses were completed by the intention-to-treat principle. Descriptive statistics was used to estimate mean (with SD) baseline and demographic characteristics and to estimate the mean (with SD) primary and secondary outcome scores at baseline and at the 12-week follow up.
Linear regression analysis adjusting for baseline SPADI was applied with the SPADI score at 12 weeks as the dependent variable to evaluate the between group differences for the patients who received HSR vs. the patient who received supervised exercises. The same analysis was also applied for the secondary outcomes.
To estimate effect of treatment by the SPADI score, 19.718 points (SDC) on the SPADI score was used as the smallest detectable change between baseline and 12-week follow up. Likewise, 11.8 points20 on the DASH score was used as the smallest detectable change. Binary logistic regression was used to compare the number of patients achieving SDC in the two groups and the OR (95%) was calculated.
Paired sample t-test was used to evaluate the change in outcomes, not divided by groups.