What is slumped sitting? A kinematic and electromyographical evaluation
Slumped sitting posture is one of the most generally identified and has been studied in asymptomatic pain-free and clinical back pain subjects. However, slumped sitting has never been clearly characterised in terms of movements and muscle activation.
The aim of this study was to quantify slumped sitting in terms of range of motion (ROM) and electromyographic measures. Twelve pain-free asymptomatic male subjects were recruited. ROM was measured on four regions of the thoracic and lumbar spine plus the pelvis; EMG was measured for 8 muscles. These measures were repeated and compared in upright sitting, slumped sitting, and maximum spinal seated flexion.
Results show slumped posture is characterised by approx. 10° of posterior pelvic tilt, full flexion of the mid- and lower- thoracic regions, and half-range of flexion of the upper-thoracic and lumbar regions. Reduced patterns activity were found in thoracic and lumbar erector spinae muscles.
The lumbar spine was previously considered to be in full flexion during slumped sitting, but this was actually never compared to maximal seated flexion. The mid- and lower-thoracic regions are actually in end-range of flexion; this may clarify how load is transferred from active to passive structures and tissues, and emphasises the role of the thoracic spine on posture. > From: Nairn et al., Man Ther 18 (2013) 498-505.
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