The effect of humeral torsion on rotational range of motion in the shoulder and throwing performance.
The orientation of the humeral head and the axis of the elbow are aligned in an angle, which is often coined either humeral retroversion or humeral torsion, depending on the angle that is measured. The term humeral torsion represents the angle measured at an intersection between a line that divides the humeral head in two even parts and a line running through the medial and lateral epicondyle of the humerus. When this angle is measured in the opposite direction, the humeral retroversion is obtained.
Habitual throwing activity can cause individuals to acquire a decrease in humeral torsion, subsequently leading to a gain in external rotation and a corresponding decrease in internal rotation – this probably a functional morphological adaptation allowing an increase in overhead throwing performance: glenohumeral internal rotation is an important factor determining power generation during throwing and an increased ROM towards external rotation might facilitate acceleration of the arm and torque production at the shoulder > from Roach et al., J Anat 220 (2012) 293-301. All rights reserved to The Authors.
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