Ann Rehabil Med.  2016 Apr;40(2):318-325. 10.5535/arm.2016.40.2.318.

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

Affiliations
  • 1Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea. minkh@chamc.co.kr

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.
CONCLUSION
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.

Keyword

Posture; Kyphosis; Shoulder; Electromyography

MeSH Terms

Area Under Curve
Arm
Electromyography
Humans
Isometric Contraction
Kyphosis
Male
Muscle Fatigue
Muscles
Musculoskeletal Pain
Posture*
Risk Factors
Scapula
Shoulder
Superficial Back Muscles*

Figure

  • Fig. 1 The measurement of Shoulder Pain and Disability Index. (A) Numeric rating scale, (B) Shoulder Pain and Disability Index.

  • Fig. 2 Two clinical tests for the assessment of scapular positioning: (A) the distance between the posterior border of the acromion and the table in the supine position, (B) the distance between the medial border and the fourth thoracic spinous process.

  • Fig. 3 Upright sitting and slouched sitting position: (A) resting upright sitting position, (B) upright sitting position with shoulder abduction, (C) resting slouched sitting position, and (D) slouched sitting position with shoulder abduction.

  • Fig. 4 Recording sites of surface electromyography (EMG) and measurement timing of muscle activation. (A) Serratus anterior (SA), middle trapezius (MT), lower trapezius (LT) and latissimus dorsi (LD). (B) Area under curve (mV·ms) was measured for 6 seconds.

  • Fig. 5 Measurement sites of thoracic kyphosis. (A) The level of 1st and 2nd thoracic spine. (B) The level of 12th thoracic spine and 1st lumbar spine. Thoracic kyphosis=(A) angle+(B) angle.

  • Fig. 6 Differences of muscle activities between upright and slouched sitting positions (n=10). Values are presented as mean±standard deviation. SA, serratus anterior; MT, middle trapezius; LT, lower trapezius; LD, latissimus dorsi. *p<0.05 by Wilcoxon signed-rank test.


Reference

1. Dolan KJ, Green A. Lumbar spine reposition sense: the effect of a 'slouched' posture. Man Ther. 2006; 11:202–207. PMID: 16621667.
Article
2. Kleine BU, Schumann NP, Bradl I, Grieshaber R, Scholle HC. Surface EMG of shoulder and back muscles and posture analysis in secretaries typing at visual display units. Int Arch Occup Environ Health. 1999; 72:387–394. PMID: 10473838.
Article
3. Mirbagheri SS, Rahmani-Rasa A, Farmani F, Amini P, Nikoo MR. Evaluating kyphosis and lordosis in students by using a flexible ruler and their relationship with severity and frequency of thoracic and lumbar pain. Asian Spine J. 2015; 9:416–422. PMID: 26097657.
Article
4. Snijders CJ, Hermans PF, Niesing R, Jan Kleinrensink G, Pool-Goudzwaard A. Effects of slouching and muscle contraction on the strain of the iliolumbar ligament. Man Ther. 2008; 13:325–333. PMID: 17553728.
Article
5. Caneiro JP, O'Sullivan P, Burnett A, Barach A, O'Neil D, Tveit O, et al. The influence of different sitting postures on head/neck posture and muscle activity. Man Ther. 2010; 15:54–60. PMID: 19643658.
Article
6. Finley MA, Lee RY. Effect of sitting posture on 3-dimensional scapular kinematics measured by skinmounted electromagnetic tracking sensors. Arch Phys Med Rehabil. 2003; 84:563–568. PMID: 12690596.
Article
7. Imagama S, Hasegawa Y, Wakao N, Hirano K, Muramoto A, Ishiguro N. Impact of spinal alignment and back muscle strength on shoulder range of motion in middle-aged and elderly people in a prospective cohort study. Eur Spine J. 2014; 23:1414–1419. PMID: 24578093.
Article
8. Nijs J, Roussel N, Vermeulen K, Souvereyns G. Scapular positioning in patients with shoulder pain: a study examining the reliability and clinical importance of 3 clinical tests. Arch Phys Med Rehabil. 2005; 86:1349–1355. PMID: 16003663.
Article
9. Brumitt J. Scapular-stabilization exercises: early-intervention prescription. Athl Ther Today. 2006; 11:15–18.
Article
10. Voight ML, Thomson BC. The role of the scapula in the rehabilitation of shoulder injuries. J Athl Train. 2000; 35:364–372. PMID: 16558649.
11. Ludewig PM, Reynolds JF. The association of scapular kinematics and glenohumeral joint pathologies. J Orthop Sports Phys Ther. 2009; 39:90–104. PMID: 19194022.
Article
12. Escamilla RF, Yamashiro K, Paulos L, Andrews JR. Shoulder muscle activity and function in common shoulder rehabilitation exercises. Sports Med. 2009; 39:663–685. PMID: 19769415.
Article
13. Bullock MP, Foster NE, Wright CC. Shoulder impingement: the effect of sitting posture on shoulder pain and range of motion. Man Ther. 2005; 10:28–37. PMID: 15681266.
Article
14. Kanlayanaphotporn R. Changes in sitting posture affect shoulder range of motion. J Bodyw Mov Ther. 2014; 18:239–243. PMID: 24725793.
Article
15. Lewis JS, Valentine RE. Clinical measurement of the thoracic kyphosis. A study of the intra-rater reliability in subjects with and without shoulder pain. BMC Musculoskelet Disord. 2010; 11:39. PMID: 20193055.
Article
16. Lee HS, Shim JS, Lee ST, Kim M, Ryu JS. Facilitating effects of fast and slope walking on paraspinal muscles. Ann Rehabil Med. 2014; 38:514–522. PMID: 25229030.
Article
17. Cools AM, Witvrouw EE, De Clercq GA, Danneels LA, Willems TM, Cambier DC, et al. Scapular muscle recruitment pattern: electromyographic response of the trapezius muscle to sudden shoulder movement before and after a fatiguing exercise. J Orthop Sports Phys Ther. 2002; 32:221–229. PMID: 12014826.
Article
18. Holtermann A, Roeleveld K, Mork PJ, Gronlund C, Karlsson JS, Andersen LL, et al. Selective activation of neuromuscular compartments within the human trapezius muscle. J Electromyogr Kinesiol. 2009; 19:896–902. PMID: 18585928.
Article
19. Park SY, Yoo WG. Differential activation of parts of the latissimus dorsi with various isometric shoulder exercises. J Electromyogr Kinesiol. 2014; 24:253–257. PMID: 24462394.
Article
20. Beaudette SM, Unni R, Brown SH. Electromyographic assessment of isometric and dynamic activation characteristics of the latissimus dorsi muscle. J Electromyogr Kinesiol. 2014; 24:430–436. PMID: 24735642.
Article
21. Noguchi M, Chopp JN, Borgs SP, Dickerson CR. Scapular orientation following repetitive prone rowing: implications for potential subacromial impingement mechanisms. J Electromyogr Kinesiol. 2013; 23:1356–1361. PMID: 24055533.
Article
22. Ludewig PM, Cook TM. Alterations in shoulder kinematics and associated muscle activity in people with symptoms of shoulder impingement. Phys Ther. 2000; 80:276–291. PMID: 10696154.
Article
23. McLean L. The effect of postural correction on muscle activation amplitudes recorded from the cervicobrachial region. J Electromyogr Kinesiol. 2005; 15:527–535. PMID: 16150608.
Article
24. Poppen NK, Walker PS. Normal and abnormal motion of the shoulder. J Bone Joint Surg Am. 1976; 58:195–201. PMID: 1254624.
Article
25. Bagg SD, Forrest WJ. A biomechanical analysis of scapular rotation during arm abduction in the scapular plane. Am J Phys Med Rehabil. 1988; 67:238–245. PMID: 3196449.
26. Ludewig PM, Cook TM. The effect of head position on scapular orientation and muscle activity during shoulder elevation. J Occup Rehabil. 1996; 6:147–158. PMID: 24234976.
Article
27. Weon JH, Oh JS, Cynn HS, Kim YW, Kwon OY, Yi CH. Influence of forward head posture on scapular upward rotators during isometric shoulder flexion. J Bodyw Mov Ther. 2010; 14:367–374. PMID: 20850044.
Article
Full Text Links
  • ARM
Actions
Cited
CITED
export Copy
Close
Share
  • Twitter
  • Facebook
Similar articles
Copyright © 2024 by Korean Association of Medical Journal Editors. All rights reserved.     E-mail: koreamed@kamje.or.kr