The effect of latissimus dorsi and teres major muscle length on shoulder flexion in throwers

Abstract

BACKGROUND: Overhead throwing action produces severe stress on joints, bones, and muscles of the upper extremity. Optimal length of latissimus dorsi and teres major muscles is prerequisite to allow full elevation of scapula and lateral rotation of humerus. Repetitive overhead throwing with the shortened muscles would cause undue stress in shoulder joint to accomplish the task.METHODS: Seventy-five overhead asymptomatic athletes from different sports were included. Player was in crook lying and smartphone clinometer was used to measure shoulder flexion. To measure latissimus dorsi length Pressure biofeedback was placed at the lower back to monitor pelvic tilt and medial rotation of the humerus was observed during flexion. For teres major length, scapular abduction, and medial rotation of the humerus was observed. The measurement was done on the non-throwing arm as well.RESULTS: Shoulder flexion on the throwing arm was 143.7° (IQR-141.7°, 149°, P value <0.001) and on non-throwing arm was 158° (IQR-154.3°,161.7°, P value <0.001) for latissimus dorsi. Meanwhile, flexion on throwing arm was 144.7° (IQR-143.3°, 146.7°, P value <0.001) and on non-throwing arm was 151.3° (IQR-149.7°, 153.3°, P value <0.001) for teres major.CONCLUSIONS: The present study has concluded that there was a significant reduction in throwing arm shoulder flexion due to shortened latissimus dorsi and teres major muscles in asymptomatic overhead throwers.