title: Changes in Activation of Serratus Anterior, Trapezius and Latissimus Dorsi With Slouched Posture.
abstract: OBJECTIVE
  To 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.
  
  
  METHODS
  Ten 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.
  
  
  RESULTS
  Activities 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.
  
  
  CONCLUSIONS
  Because 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.
authors.affiliation: Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: Seok Tae
authors.initials: ST
authors.lastname: Lee
authors.affiliation: Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: Jinkyoo
authors.initials: J
authors.lastname: Moon
authors.affiliation: Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: Seung Hoon
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: Kye Hee
authors.initials: KH
authors.lastname: Cho
authors.affiliation: Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: Sang Hee
authors.initials: SH
authors.lastname: Im
authors.affiliation: Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: MinYoung
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: Kyunghoon
authors.initials: K
authors.lastname: Min
keywords: Electromyography; Kyphosis; Posture; Shoulder