Changes in supraspinatus and biceps tendon thickness: influence of fatiguing propulsion in wheelchair users with spinal cord injury

STUDY DESIGN: Quasi-experimental, pretest-posttest design. OBJECTIVES: To identify acute changes in the supraspinatus and biceps tendon following fatiguing wheelchair propulsion and to associate tendon changes with risk factors associated with shoulder pain in persons with spinal cord injury (SCI). SETTING: Biomechanical laboratory Swiss Paraplegic Research. METHODS: A population-based sample of 50 wheelchair users with SCI at lesion level T2 or below participated. Fatigue was measured using the rate of perceived exertion and heart rate. Linear regression techniques were used to assess the association between the dependent and independent variables. Dependent variables included absolute differences in supraspinatus and biceps tendon thickness, contrast and echogenicity ratio assessed with ultrasound before and after a fatiguing wheelchair propulsion intervention. Independent variables included: susceptibility to fatigue (Yes/No), the acromio-humeral distance, sex, time since injury, activity levels and body weight. RESULTS: A reduction in supraspinatus tendon thickness after fatiguing wheelchair propulsion (−1.39 mm; 95% CI: −2.28; −0.51) was identified after controlling for all potential confounders. Females who fatigued (n=4) displayed a greater reduction in supraspinatus tendon thickness as compared to those who did not fatigue (n=7). In contrast, higher body weight was associated with an increase in supraspinatus tendon thickness and a greater acromio-humeral distance before the intervention was associated with an increase in biceps tendon thickness. CONCLUSIONS: Acute changes in the supraspinatus and biceps tendon after fatiguing wheelchair propulsion may explain the high prevalence of tendon injuries in this population. Future research should determine the consequences of tendon changes and its relationship to tendinopathy.