Investigation of muscular activation around the scapula in closed kinetic chain exercises using different shoulder joint angles

There are evidence regarding the importance and role of the kinetic chain approach in shoulder rehabilitation in the recent literature. Closed kinetic chain (CKC) exercises aim to improve functional joint stability and neuromuscular control by allowing co-contraction of the shoulder and scapular muscles. The aim of research was to examine the muscular activation and activation ratios around the scapula in CKC exercises performed with different glenohumeral joint (GHJ) angles. Twenty-two healthy and physically active male individuals (age: 19.41.5 years; body mass index: 23.62.3kg/m2) were included in this study. CKC exercises categorized as below shoulder level (GHJ<90o), shoulder level (GHJ~90o) and above shoulder level (GHJ>90o) according to glenohumeral joint elevation in the sagittal plane. Eight different exercises were performed randomly by the participants. During these exercises, the activation levels of the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT) and serratus anterior (SA) muscles were evaluated by surface electromyography. Repeated Measures Analysis of Variance (ANOVA) was used to compare muscle activation levels and UT/MT, UT/LT, and UT/SA ratios among conditions. The exercises were compared, significant differences were found in scapular muscle activations and activation rates (p<0.05). High levels of SA muscle activation (%44.6 MVIC) was observed in the concentric phase of Low plank plus exercise performed at shoulder level, whereas UT and OT muscle activation was found higher in Pike press which performed above shoulder level when compared to other exercises. All tested exercises provided an optimal (<1.00) UT/SA activation ratio; however, only Body saw exercise provided optimal UT/LT activation ratio. The results of this research will provide basic science for the selection of exercises that targets neuromuscular control in shoulder rehabilitation.