Tolerance and effectiveness of eccentric vs. concentric muscle strengthening in rotator cuff partial tears and moderate to severe shoulder pain. A randomized pilot study.

INTRODUCTION

Rotator cuff tears are the main cause of shoulder pain and disability. First line of treatment is conservative; there is evidence regarding the advantage of using eccentric over concentric exercises in tendinopathies, but there are no evidence-based recommendations on starting strengthening exercise during painful phases nor on the effectiveness and advantages of eccentric vs. concentric exercise in rotator cuff tears.

OBJECTIVE

To evaluate the tolerance of a resistance strengthening program and to compare eccentric vs. concentric programs.

DESIGN

A pilot, experimental, randomized controlled study.

SETTING

Outpatient Rehabilitation Center.

PATIENTS

Twenty-six patients with a diagnosis of partial rotator cuff tear were randomly assigned to: the experimental group (eccentric,  = 12) and the control (concentric,  = 14).

INTERVENTION

The experimental group performed muscle strengthening with eccentric technique directed to shoulder and scapular girdle muscles, while the control group performed the concentric technique.

MAIN OUTCOME MEASURES

Visual Analogue Scale (VAS), Constant Scale, Strength, Structure (Ultrasound report).

RESULTS

The tolerance rate was 96% in both groups. Median age (experimental vs. control) was 54.5 vs. 54 years ( = 0.69). Results at baseline, and at months 1, 3, and 12 (median) were as follows: for VAS (mm), experimental: 55, 30, 30, and 10,  < 0.001 (intra-group); control: 50, 30, 30, and 5,  = 0.01; Constant scale (points): experimental 58.5, 88, 93, and 85,  < 0.001; control 50.62, 80, and 91.5,  = 0.038; normalized strength (Kg); experimental: 0.23, 0.29, 0.73, and 0.72,  = 0.001, and control: 0.24, 0.21, 0.54, and 0.66,  = 0.01. We found inter-group differences in the Constant scale at 1 and 3 months ( < 0.05), and in strength at months 1 and 3 ( < 0.05). We observed structural differences in tendon (healing) between groups at 3 and 12 months.

CONCLUSIONS

Eccentric and concentric strengthening were well tolerated; both show early improvement in pain, functionality and tendon structure. Eccentric training appears to be more effective than concentric in the early improvement of functionality, strength and tendon healing.