Comparison of Back Electromyographic Activity during Sitting Sideways Between Flat and Inclined Floor

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Parinya Lertsinthai Kanphajee Sornkaew


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.


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Lertsinthai P, Sornkaew K. Comparison of Back Electromyographic Activity during Sitting Sideways Between Flat and Inclined Floor. Thai Journal of Physical Therapy [Internet]. 15Aug.2015 [cited 22Mar.2018];37(2):78-0. Available from:
Research Articles


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