Altered Cervical Spine Position Results in Decreased Eccentric Shoulder Rotation Strength.

Abstract

Overhead athletics require strenuous shoulder activity in nonneutral cervical spine positions to eccentrically decelerate the throwing/striking arm following ball release/contact. Therefore, we aimed to compare eccentric shoulder rotation strength through a 90° arc between neutral and rotated positions. 52 participants (19M,34F170±10cm;73±18kg,21.9±2.9years) without shoulder or cervical spine pathology participated. Isokinetic eccentric shoulder rotation strength was measured through a 90° arc with shoulder elevated 90° in frontal plane (frontal plane), and 45° anterior to the frontal plane (scapular plane) in neutral and rotated cervical spine positions. Frontal plane eccentric external rotation strength differed between neutral and contralaterally positions in the first 10° of the motion, near forearm vertical (p=0.029). Cervical spine position was obtained by instructing participants to maximally rotate their respective side. Internal rotation strength differed between neutral and contralaterally rotated positions from 55-60° external rotation (p=0.004). Scapular plane eccentric external rotation differed between cervical positions between 21-67° shoulder external rotation (p<0.001). Scapular plane internal rotation strength differed between cervical positions between 22-60° shoulder external rotation (p<0.001). In populations requiring strenuous use of their shoulders in altered cervical spine positions, sports medicine clinicians should consider including strength testing reflecting the functional positions of their patients during an orthopedic examination.