Adaptation of muscle activity in scapular dyskinesis test for collegiate baseball players.
BACKGROUND
The characteristics of scapular muscle activities in elevation and descent exercises have yet to be elucidated to assess scapular dyskinesis. The purpose of this study was to identify the adaptation of electromyograph (EMG) activities of the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and anterior deltoid (AD) muscles with different weight loads in flexion (FLX) and abduction (ABD) in collegiate baseball players.


METHODS
Twenty eight individuals, including 13 pitchers, were tested. Normalized EMG signals for the UT, LT, SA, AD muscle of the both the dominant (DOM) and nondominant (NON) side were blocked at every 1 second during each of the exercises. A 3-way repeated analysis of variance design was used to identify differences in the mean values between DOM and NON and between FLX and ABD for DOM.


RESULTS
The mean EMG value of the UT in the DOM was significantly less than that of the NON for all joint angles (P < .01), whereas the mean EMG value of the LT in the DOM was significantly greater than that of the NON (P < .01). In contrast, no difference in the SA EMG activity was determined between DOM and NON. However, the mean EMG value of SA in FLX was significantly greater than in ABD (P < .01).


CONCLUSIONS
This study identified an apparent adaptation of scapular muscle activities in the currently advocated scapular dyskinesis test for healthy active overhead athletes who are vulnerable to shoulder pathologies.
Department of Kinesiology, San José State University, San José, CA, USA. Electronic address: masaaki.tsuruike@sjsu.edu.
Masaaki
M
Tsuruike
Physiotherapy Associates Scottsdale Sports Clinic, Scottsdale, AZ, USA.
Todd S
TS
Ellenbecker
D000222:Adaptation, Physiological; D001484:Baseball / Q000502:physiology*; D004576:Electromyography; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012540:Scapula / Q000502:physiology*; D012782:Shoulder / Q000502:physiology*; D014495:Universities; D055815:Young Adult
Baseball players; Bilateral comparison; EMG; Lower trapezius; Muscular adaptation; Scapular dyskinesis test; Upper trapezius