Assessing Scapular Muscle Strength and Force Couple Ratios in Stroke Patients: A Cross-Sectional Study

Introduction: This study quantifies the differences in individual scapular muscle strength in both arms along with obtaining a force couple ratio of scapula stabilizers to gain values in terms of the strength of muscles. Materials and Methods: A quantitative cross-sectional study was done on 30 stroke patients to assess the muscle strength of the serratus anterior, rhomboids, and upper, middle, and lower trapezius (in both shoulders) using a suspension scale. Meanwhile, the muscle force couple ratios were calculated. Results: The results showed significant strength differences between both arms for upper trapezius (P=0.0020), serratus anterior (P=0.018), rhomboids (P=0.001), middle trapezius (P=0.0068), and no difference for lower trapezius (P=0.1746). The mean muscle strength in the non-affected arm is greater than the affected arm. The middle trapezius strength is lowest in the affected arm (0.574 kgf) and the lower trapezius strength is lowest in the non-affected arm (0.767 kgf). The mean force couple ratio for upper trapezius versus lower trapezius was higher in the affected side (10.08) and the non-affected side (7.74). The remaining force couples were similar for both arms. Conclusion: Overall muscle strength of the scapula stabilizers is greater in the non-affected arm than in the affected arm. The strength of the force couple between the upper and lower trapezius is greater in both arms which shows considerable incoordination between the muscles.