Changes in Activation of Serratus Anterior, Trapezius and Latissimus Dorsi With Slouched Posture

Abstract

ObjectiveTo compare quantitative muscle activation between erect and slouched sitting postures in the muscles around the scapula, and to investigate the correlation between the angle of thoracic kyphosis and the alteration of muscle activity depending on two different sitting postures.MethodsTen healthy males participated in the study. Unilateral surface electromyography (SEMG) was performed for serratus anterior, middle trapezius (MT), and lower trapezius (LT), which are scapular stabilizer muscles, as well as latissimus dorsi. Participants elevated their shoulders for 3 seconds up to 90° abduction in the scapular plane, tilting 30° anterior in the coronal plane. They were told to hold the position for 10 seconds and voluntary isometric contractions were recorded by SEMG. These movement procedures were conducted for three times each for erect and slouched sitting postures and data were averaged.ResultsActivities of MT and LT increased significantly more in the slouched sitting posture than in the erect one. There was no significant correlation between kyphotic angle and the area under curve of each muscle.ConclusionBecause MT and LT are known as prime movers of scapular rotation, the findings of this study support the notion that slouched sitting posture affects scapular movement. Such scapular dyskinesis during arm elevation leads to scapular stabilizers becoming overactive, and is relevant to muscle fatigue. Thus, slouched sitting posture could be one of the risk factors involved in musculoskeletal pain around scapulae.

Association Between Forward Head, Rounded Shoulders, and Increased Thoracic Kyphosis: A Review of the Literature

“…[21][22][23] Electromyography is also very commonly used in postural assessment studies to ascertain the changes in muscular activities that occur as a result of postural changes. 24 Most previous studies mention the causes and consequences of FHP, rounded shoulders, and increased thoracic kyphosis. However, there is a dearth of studies focused on the association between forward head, rounded shoulders, and hyperkyphosis.…”

Scapular Dyskinesis: From Basic Science to Ultimate Treatment

“…Pain could also be affected by musculoskeletal factors, such as a slouched sitting posture. In sedentary young adult males, it has been demonstrated that changing a specific position may influence pain level [31,32]. Altered scapular kinematics could be linked to pain in the region of the neck [33].…”

Thera-Band application changes muscle activity and kyphosis and scapular winging during knee push-up plus in subjects with scapular winging

“…Hyperkyphosis causes excessive scapular protraction and downward rotation. [ 11 , 12 ] Thoracic erector spinae (TES) and rectus abdominis (RA) muscle activity are affected by trunk posture [ 13 ] ; especially, a flexed trunk posture inhibits TES and shortens RA. In addition, previous studies reported that TK is positively associated with forward head posture (FHP).…”