Main Article Content
The purpose of this study was to compare surface electromyography (sEMG) of back muscle activities (Multifidus; MF and Iliocostalis lumborum; IL), between sideways sitting on the flat and inclined floor. Fifteen healthy volunteers (2 males, 13 females) were recruited with average age 21.01±1.98 years and 21.02±1.89 kg./m.2of body mass index (BMI). The volunteers were asked to sit in sideways pose on their preferred side. Noticeably, they were all sitting on their non-dominant leg. The adjusted tilt angle of inclined floor was done individually by using the volunteer’s feeling of comfort. The angle of inclined floor was 11.33±2.79 degrees where the volunteers felt the most comfortable sideways sitting. The percent of maximum voluntary contraction (%MVIC: µv) between back muscle activities (MF and IL) of the concave and convex sides of spine were compared, while sitting on the flat and inclined floor. The results showed that there was no significantly different between back muscle activities of the concave and convex sides of spine (p>0.05) in both sideways sitting positions. Exception, only %MVIC of MF at concave side of spine was significantly decreased in sitting on the inclined floor as compared with sitting on the flat floor (p<0.05).
In conclusion, the volunteers felt more comfortable during sideways sitting on the inclined floor. The sideways sitting on inclined floor showed that the %MVIC of MF on the concave side of spine was decreased and muscular activities of MF on both sides were more likely balanced compared with sideways sitting on the flat floor.
2. Thai etiquette: Sitting [Internet]. 2015 [cited 2015 Mar 16]. Available from: http://www.seameo.org/vl/thaiet/index1.htm.
3. Norkin CC, Levangie PK. Basic concepts in biomechanics. In: Norkin CC and Levangie PK, editors. Joint structure and function: a comprehensive analysis. 2nd ed. Philadephia: F.A. Davis company; 1992. p.1-56.
4. de Looze MP, Kuijt-Everst LF, van Dieen JV. Sitting comfort and discomfort and the relationship with objective measures. Ergonomics 2003;46(10):985-97.
5. Skaggs DL. Adolescent idiopathic scoliosis: an update. Am Fam Physician 1996;May(15):2327-35.
6. Greiner KA. Adolescent idiopathic scoliosis: radiologic decision-making. Am Fam Physician 1996;May(15):2327-35.
7. Valachi B, Valachi K. Mechanism leading to musculoskeletal disorders in dentistry. J Am Dent Assoc 2003; 134:1344-50.
8. ภานุพันธ์ ทรงเจริญ. กลุ่มอาการเส้นประสาทถูกกดทับในส่วนขา. ใน: ภานุพันธ์ ทรงเจริญ, บรรจง มไหสวริยะ บรรณาธิการ การบาดเจ็บของเส้นประสาท. กรุงเทพฯ เรือนแก้วการพิมพ์; 2539.หน้า 247-79.
9. Greendale GA, Nili NS, Huang MH, Seeger L, Karlamangla AS. The reliability and validity of three non-radiological measures of thoracic kyphosis and their relations to the standing radiological Cobb angle. Osteoporos Int 2011;22(6):1897-905.
10. Rheault W, Ferris S, Foley JA, Schaffhauser D, Smith R. Intertester reliability of the flexible ruler for the cervical spine. J Orthop Sports Phys Ther 1989;10(7):254-6.
11. Fridlund AJ, Cacioppo JT. Guidelines for human electromyographic research. Psychophysiology 1986;23(5):567-89.
12. Cram JR, Kasman GS, Holtz J. Introduction to surface electromyography. 1st ed. Maryland: Aspen publishers. Inc; 1998.
13. Merletti R, Rainoldi A, Farina D. Surface electromyography for noninvasive characterization of muscle. Exercise and Sport Sciences Reviews 2001;29(1):20-5.
14. Ng JK, Richardson CA. Reliability of electromyographic power spectral analysis of back muscle endurance in healthy subjects. Arch Phys Med Rehabil 1996;77:259-64.
15. Dankaerts W, O’Sullivan PB, Burnett AF, et al. Reliability of EMG measurements for trunk muscles during maximal and sub-maximal voluntary isometric contractions in healthy controls and CLBP patients. Journal of Electromyography and Kinesiology 2004;14(3):333-42.
16. Ng JK, Richardson CA, Jull GA. Electromyographic amplitude and frequency changes in the iliocostalis lumborum and multifidus muscles during a trunk holding test. Phys Ther 1997;77(9):954-61.
17. Velotta J, Weyer J, Ramirez A, Winstead J, Bahamonde R. Relationship between leg dominance tests and type of task. Portuguese Journal of Sport Sciences 2011;11(suppl 2):1035-8.
18. Hoffman M, Schrader J, applegate T, Koceja D. Unilateral postural control of the functionally dominant and nondominant extremities of health subjects. J Athel Train1998:33(4):319-22.
19. Geffen P, Veltink PH, Koopman BF. Can pelvis angle be monitored from seat support forces in healthy subjects? 2009 J Biomech Eng [Internet]. [cited 2015 Mar 1];131(3):034502. Available from: http://biomechanical.asmedigitalcollection.asme.org/article.aspx?articleid=1423952
20. van Geffen P, Reenalda J, Veltink PH, Koopman BF. Decoupled pelvis rotation in sitting: a passive motion technique that regulates buttock load associated with pressure ulcer development. J Biomech 2009 ;42(9):1288-94.
21. Kurazumi Y, Matsubara N, Horikoshi T. Effect of posture on the heat transfer areas of the human body. Building and Environment 2008;43(10):1555-65.
22. Massion J. Postural control system. Curr Opin Neurobiol 1994;4(6):877-87.
23. Anderson SM. Spinal curves and scoliosis. Radiol Technol 2007;79(1):44-65.
24. Taft E, Francis R. Evaluation and management of scoliosis. J Pediatr Health Care 2003;17(1):42-4.
25. Fidler MW, Jowett RL. Muscle imbalance in the aetiology of scoliosis. Journal of bone and joint surgery 1976; 2:6-7.
26. Cassidy JD, Brandell BR, Nykoliation JW, Wedge J. The role of paraspinal muscle in the pathogenesis of idiopathic scoliosis: a preliminary EMG study. JCCA 1987;31(4): 179-84.
27. Ng JK, Richardson CA, Kippers V, Parnianpour M. Relationship between muscle fiber composition and functional capacity of back muscles in healthy subjects and patients with back pain. J Orthop Sports Phys Ther 1998;27(6):389-402.
28. O'Sullivan PB, Grahamslaw KM, Kendell M, Lapenskie SC, Moller NE, Richards KV. The effect of different standing and sitting postures on trunk muscle activity in a pain-free population. Spine 2002;27(11):1238-44.
29. Ng JK, Richardson CA. Reliability of electromyographic power spectral analysis of back muscle endurance in healthy subjects. Arch Phys Med Rehabil 1996; 77(3): 259-64.
30. Bergmark A. Stability of the lumbar spine. A study in mechanical engineering. Acta Orthop Scand Suppl 1989; 230: 1-54.