Effect of Exercise Position on Percent Changes in Serratus Anterior Muscle Thickness

Abstract

Open Access Research Articleassessment tools have limitations. Techniques used to manual muscle test the SA are easy to perform but do not appear to isolate the SA [5]. ElectroMyographic Activity (EMG) and motion analysis provide researchers with isolated and detailed information but interpretation is difficult [7,8]. Unlike other assessment tools, Ultrasound Imaging (UI) provides isolated real time visualization of muscle contraction, thus allowing researchers and clinicians quick interpretation of the contraction of a specific muscle [9,10]. UI has been shown to be a valid and reliable assessment tool for measuring thickness and cross sectional areas of the transversus abdominus, obliques [11] A few studies have investigated muscle thickness measures of the SA in both healthy [16][17][18] and pathological populations [19]. In general, between and within day intra-rater reliability measuring SA thickness has been shown to be good to excellent in health individuals positioned in glenohumeral scaption [16,17]. Only one study has investigated inter rater reliability of SA thickness and the results were modest to poor [17].Other studies have investigated the ability to detect changes in SA thickness using UI. Two studies found no differences in healthy individuals when adding various loads to the UE in scaption at both 90 degrees [16], and 120 degrees of elevation [18]. However, increasing loads during upper extremity elevation does not appears to effect EMG activity of the serratus anterior [20] and therefore, may explain why no changes in the SA thickness were observed between loads using diagnostic ultrasound imaging. One other study has investigated SA muscle thickness in patients with LE compared to controls. Preliminarily and with a small sample size, it appears that UI was able to detect significant differences in the change of muscle thickness from rest to contraction when comparing patients to controls but the mean differences were not beyond minimal detectable change values [16]. Another manuscript by Seitz et al, reported no significant differences in SA muscle thickness in health individuals with and without observable scapular dyskinesia [21].With the available evidence in UI assessment of the SA, it AbstractObjective: A reliable method for measuring SA thickness with ultrasound imaging has been reported, yet the ability to detect differences in levels of contractility has yet to be established. The purpose of this study was to determine if there are differences in the percent change in thickness of the SA during four different exercise positions performed by healthy individuals. Design: Observational study Setting: LaboratoryParticipants: Twenty-eight healthy participants, mean age 26 (SD 4, 57% female, 100% right handed) Methods: Volunteers were positioned in a standardized sitting posture and anatomical landmarks were marked for ultrasound probe positioning. Two resting and two contractile ultrasound images were taken for each exercise position and the average thickness between trials was used in th...