Electromyographic Analysis of Scapular Muscles During Closed Kinetic Chain Exercises

Overview

In shoulder rehabilitation, the inclusion of kinetic chain exercises is advocated in order to provide the necessary energy transfer to produce optimal force with minimal energy consumption. Closed kinetic chain (CKC) exercises are defined as exercises in which the distal segment is stabilized by encountering significant resistance while the proximal segment moves. In contrast, open kinetic chain (OKC) exercises allow the distal segment to move freely without any resistance. Recently, the importance of closed kinetic chain (CKC) exercises has increased in enhancing shoulder joint neuromuscular control by improving dynamic shoulder stability and joint position sense. The most current shoulder rehabilitation protocols include exercises for restoration of scapular muscle imbalances.There exist studies investigating the levels of scapular muscle activation during CKC exercises. Researchers have shown that most CKC exercises especially push-ups and plank variations with the shoulder in the 90° position, generally provide high SA activity and an optimal UT/SA ratio.In the literature, there is limited information on how the level of shoulder elevation affects scapular muscle activity and ratio during closed kinetic chain exercises in the prone position. To effectively prescribe CKC exercises commonly used in rehabilitation and athletic programs, a clear understanding of shoulder elevation changes muscle activity during these exercises is required. Our hypothesis is that glenohumeral joint elevation status will alter scapular muscle activation and activation rates.

Twenty-two healthy male individuals to recruited in the study. Conducting a power analysis through G∗Power, considering a moderate effect size (f = 0.25), an alpha level of 0.05, and a power of 0.8. The outcome of this analysis indicated a required minimum sample size of 21 individuals. This study was used a randomized, repeated measures cross-over design. Muscle activation levels during maximum voluntary isometric contraction (MVIC) of each muscle (Upper trapezius, Middle trapezius, Lower trapezius, Serratus anterior) will be recorded to normalize muscle activation levels during closed kinetic chain exercises. Muscle activation levels will be evaluated with a surface electromyography device (Noraxon, Myomotion, USA).