Active Scapular Retraction and Acromiohumeral Distance at Various Degrees of Shoulder Abduction.

CONTEXT:   Performing shoulder-abduction exercises with scapular retraction has been theorized to reduce the potential for shoulder impingement. However, objective data to support this premise are lacking.

OBJECTIVE:   To evaluate the influence of active scapular retraction on acromiohumeral distance (AHD) at 4 shoulder-abduction angles using real-time ultrasound.

DESIGN:   Cross-sectional study.

SETTING:   University laboratory.

PATIENTS OR OTHER PARTICIPANTS:   Twenty asymptomatic individuals (10 men, 10 women; age = 22.9 ± 2.8 years, height = 169.3 ± 9.5 cm, mass = 65.5 ± 12.9 kg) were recruited.

MAIN OUTCOME MEASURE(S):   Real-time ultrasound images of AHD were obtained during nonretracted and retracted scapular conditions at 0°, 45°, 60°, and 90° of shoulder abduction. A 2-factor analysis of variance with repeated measures was used to evaluate the influence of shoulder retraction on AHD across shoulder-abduction angles.

RESULTS:   A scapular-retraction condition × shoulder-abduction-angle interaction for AHD was found ( F3,57 = 4.56, P = .006). The AHD was smaller at 0° (10.5 versus 11.2 mm, respectively; t19 = 2.22, P = .04) but larger at 90° (9.4 versus 8.7 mm, respectively; t19 = -2.30, P = .04) of shoulder abduction during the retracted than the nonretracted condition. No differences in AHD were observed between conditions at 45° ( t19 = 1.45, P = .16) and 60° ( t19 = 1.17, P = .86) of abduction.

CONCLUSIONS:   The observed differences in AHD at 0° and 90° of shoulder abduction were small and did not exceed the established minimal detectable change for either angle. Our findings suggest that active scapular retraction during shoulder abduction has a minimal influence on AHD at 0° and 90° in healthy individuals. Further investigations are needed to determine whether scapular retraction influences AHD in individuals with subacromial impingement.