The relationship between latissimus dorsi stiffness and altered scapular kinematics among asymptomatic collegiate swimmers

Abstract

ObjectivesTo determine the strength of the relationship between latissimus dorsi stiffness and altered scapular kinematics among swimmers. DesignCross sectional. SettingLaboratory. ParticipantsNineteen NCAA Division III swimmers (7 male, 12 female) (age = 18.8 ± 0.9 years, height = 174.7 ± 8.9 cm, mass = 71.6 ± 11.9 kg) volunteered to participate. Subjects had no recent history of upper extremity pathology or any previous surgery. InterventionsWe measured latissimus dorsi stiffness of the dominant arm while in a lengthened position with a myotonometer. We used an electromagnetic tracking device with specialized software to measure scapular kinematics at humeral elevation angles of 30°, 60°, 90°, and 110° within the scapular plane. Main outcome measuresLatissimus dorsi stiffness and scapular upward/downward rotation, internal/external rotation, and anterior/posterior tilt. ResultsLatissimus dorsi stiffness showed moderate-to-good relationships with increased scapular upward rotation (r > −0.63, P < 0.002) and posterior tilt (r > −0.62, P < 0.004) at all four angles of humeral elevation. Increased latissimus dorsi stiffness also showed moderate-to-good relationships with decreased scapular internal rotation at humeral elevation angles of 60° (r = 0.47, P = 0.03) and 90° (r = 0.54, P = 0.01). ConclusionsOur results suggest there are several moderate-to-good relationships between increased latissimus dorsi stiffness in swimmers and altered scapular upward rotation, internal rotation, and posterior tilt at various angles of humeral elevation. If latissimus dorsi stiffness is not addressed subsequent scapular alterations, which have been associated with shoulder dysfunction, may occur.