Shoulder Kinematics Is Not Influenced by External Load During Elevation in the Scapular Plane

Abstract

The current study aimed to compare the shoulder kinematics (3D scapular orientation, scapular angular displacement and scapulohumeral rhythm) of asymptomatic participants under unloaded and loaded conditions during unilateral shoulder elevation in the scapular plane. We used a repeated-measures design with a convenience sample. Eleven male participants with an age range of 21-28 years with no recent history of shoulder injury participated in the study. The participants performed isometric shoulder elevation from a neutral position to approximately 150 degrees of elevation in the scapular plane in intervals of approximately 30 degrees during unloaded and loaded conditions. Shoulder kinematic data were obtained with videogrammetry. During shoulder elevation, the scapula rotated upwardly and externally, and tilted posteriorly. The addition of an external load did not affect 3D scapular orientation, scapular angular displacement, or scapulohumeral rhythm throughout shoulder elevation (P > .05). In clinical practice, clinicians should expect to observe upward and external rotation and posterior tilt of the scapula during their assessments of shoulder elevation. Such behavior was not influenced by an external load normalized to 5% of body weight when performed in an asymptomatic population.

Application of statistical parametric mapping for comparison of scapular kinematics and EMG

“…We also conducted interval averaging analysis and qualitatively compared to the SPM results. Mean humeral elevation angles were calculated over both 10° (Kai et al, 2016;Kon et al, 2008) and 30° intervals (Camci et al, 2013;De Castro et al, 2014;Michener et al, 2016). A Type I error rate of 0.05 was used in all tests.…”

Effect of external load on scapular upward rotation during arm elevation: the knot concept

“…In previous studies, the influence of external loads on scapular movement during arm elevation was evaluated by setting the elevation angle at intervals of 20° (de Castro et al 2014 ; Forte et al 2009 ; Kon et al 2008 ; McQuade et al 1998 ; Pascoal et al 2000 ). In contrast, we evaluated scapular upward rotation with arm elevation as a continuous movement, and were able to identify the knot by fitting the movement to a line graph using the spline function.…”

“…Similarly, Pascoal et al ( 2000 ) analyzed scapular movement using 0–4 kg loads and an electromagnetic tracking device, and reported that external load did not influence SHR. Furthermore, de Castro et al ( 2014 ) analyzed scapular movement during scapular plane elevation with a 5 % body weight load and videogrammetry, and reported that the amount of external load did not influence scapular movement. Thus, our findings are in agreement with previously reported findings.…”

“…Various studies have reported that scapular upward rotation is influenced by external loads (Forte et al 2009 ; Kon et al 2008 ; McQuade et al 1998 ). In particular, studies comparing loaded and unloaded scapular movement during arm elevation have reported that the scapular upward rotation decreased (Kon et al 2008 ; McQuade et al 1998 ), increased (Forte et al 2009 ), or was not influenced (de Castro et al 2014 ; Pascoal et al 2000 ) by the external load. Hence, there is no consensus regarding the effects of external load on scapular upward rotation.…”