Comparison of an eccentric exercise intervention to a concentric exercise intervention in adults with subacromial impingement syndrome
Blume, Christiana Lynne
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Research has demonstrated moderate evidence for exercise in the treatment of subacromial impingement syndrome (SAIS). This evidence has primarily addressed traditional concentric – eccentric resistance training with a lack of rationale for selection of contraction type, dosage, or progression of resistance. Recent literature has suggested that patients with tendinopathies respond well to eccentric training although few studies have investigated eccentric training effects on rotator cuff tendinopathy. The primary purpose of this study was to compare the effectiveness of an eccentric progressive resistance exercise (PRE) intervention to a concentric PRE intervention in adults with SAIS. The outcome measures, assessed by examiners blinded to intervention group, included the disabilities of the arm, shoulder, and hand (DASH) functional outcome score, pain-free shoulder elevation active range of motion (AROM), and pain-free shoulder abduction and external rotation strength. A secondary purpose was to determine if five or eight weeks of intervention was adequate to achieve significant changes in the shoulder outcome measures. A third purpose was to examine the correlations between the DASH and the physical measures of shoulder AROM and strength. The study was a prospective, randomized, clinical trial using a two-way, mixed design, with intervention group as the between- subjects factor and time as the within-subjects factor. Four 2x3 mixed-model, analyses of variance (ANOVA) with repeated measures were used to analyze the data from the outcome measures (α = 0.0125). Pearson correlation coefficients were calculated to describe the relationships between the DASH and the AROM and strength measurements. There were no significant interactions of treatment group by time for any of the outcome measures. Post-hoc analyses revealed a significant main effect of time on all outcome measures for all participants. The DASH scores had significant negative correlations with scaption AROM at all three time points and with both strength measurements at week five. The findings of this study indicate that supervised PRE for scapular and rotator cuff muscles performed twice a week for eight weeks may be beneficial in restoring function in patients with SAIS. These findings were true for both concentric and eccentric PRE programs.