A comparison of isometric, isotonic concentric and isotonic eccentric exercises in the physiotherapy management of subacromial pain syndrome/rotator cuff tendinopathy: Study protocol for a pilot randomised controlled trial

Abstract

Background: Subacromial pain syndrome (SPS) involving rotator cuff tendinopathy is a common cause of shoulder pain and disability. Evidence suggests that structured physiotherapy may be as effective as surgery in this condition with significant improvements demonstrated in trials involving scapular retraining, rotator cuff strengthening and flexibility exercises. Most published programs typically utilise isotonic concentric and/or eccentric strengthening modes. Recently, immediate analgesic effects and muscle strength gains following heavy-load isometric exercises in lower limb tendinopathy conditions have been observed. It is pertinent to ascertain whether such outcomes can be replicated in SPS/rotator cuff tendinopathy. The primary aim of this study is to establish the feasibility of undertaking a full-scale randomised controlled trial (RCT) that compares the effects of isometric, isotonic concentric and isotonic eccentric rotator cuff contractions when used as part of a semi-standardised exercise-based physiotherapy program in patients diagnosed with SPS. The secondary aim is to explore potential trends or treatment effects of the exercise intervention. Methods: Thirty-six participants diagnosed with SPS will be randomised to one of three intervention groups and undergo a one-on-one exercise-based physiotherapy intervention, involving scapular and rotator cuff muscle retraining and strengthening. Each group will utilise a different mode of rotator cuff strengthening-isometric, isotonic concentric or isotonic eccentric. Rotator cuff tendon responses to isometric loading are not yet established in the literature; hence, individualised, progressive loading will be used in this pilot study in accordance with symptoms. The intervention will involve two phases: during Phase 1 (weeks 1-6) participants undertake the active group-specific physiotherapy treatment; in Phase 2 (weeks 6-12), they undertake a progressive, but no longer group-specific exercise program. To determine feasibility, an evaluation of key study parameters including (a) ease of recruitment (rate and number as well as suitability of the assessment algorithm), (b) adherence to all phases of the exercise intervention including home program compliance and logbook completion, (c) participant non-completion (drop out number and rate) and (d) adverse events (nature and number) will be undertaken. Secondary outcomes will measure immediate effects: (i) within-treatment changes in pain perception (verbal rating scale (VRS) and shoulder muscle strength (hand-held dynamometer) as well as longer-term changes: (ii) shoulder-related symptoms and disability (Western Ontario Rotator Cuff Index (WORC) and Shoulder Pain and Disability Index (SPADI)), (iii) perception of pain (11-point numerical rating scale (NRS), (iv) shoulder muscle strength (hand-held dynamometer) and (v) perceived global rating of change score. The immediate within-treatment assessment of pain and muscle strength will be undertaken in treatments 2 and 3, and the longer term measures will be collected at the primary (conclusion of Phase 1 at 6 weeks) and secondary (conclusion of Phase 2 at 12 weeks) end-points of the study. Discussion: The findings of this pilot study will permit evaluation of this study design for a full-scale RCT.