Comparing Muscle Activity and Spine Shape in Various Sitting Styles

Abstract

Lower back pain is experienced by approximately 70% of the world's population, contributing to the worldwide burden of disease. Americans experience lower back pain at an estimated economic cost of $560–$635 billion. One contributing factor for back pain is posture, and more particularly, lack of awareness of dysfunctional posture. For example, many people sit in a slouched or forward-bent position, exacerbated by poor ergonomics while sitting or extended use of handheld digital devices while standing, such as looking down at a smartphone for long periods of time. This report describes a stacksitting technique that is one of the components of the Gokhale Method® for healthy, relaxed sitting and increased awareness of posture. The stacksitting process is illustrated with a case study, where the shape of the spine and the muscle activity are analyzed in parallel during three sitting styles: slouching, arched, and stacksitting. The spine curvature was characterized by the Gokhale SpineTracker™ wearable, which consists of five sensor units attached along the subjects' spines that are used to plot the spinal curve on a digital device such as a smartphone, tablet, or computer. Surface electromyographic (SEMG) recordings were made from the right upper trapezius, left upper trapezius, right midback, and left midback with a second device (Myoscan Pro sensors recorded with Biograph Procomp Infinity) while participants were seated in three postures: a slouched (forward-bent) position, an upright arched position, and an upright stacksitting position as trained by a Gokhale Method teacher. The case observations showed no significant difference in trapezius SEMG activity during each of the three positions. There was a slight increase in SEMG activity of the midback during stacksitting (1.1 μV) as compared with when slouched (0.64 μV), and a significant increase in SEMG activity when sitting arched (4.9 μV). As expected, the spinal activity tracking device showed significant straightening of the lower spine during the stacksitting position as compared with the slouched and arched positions. The observations suggest that the stacksitting position can be taught to others in a way that allows the vertebrae to be parallel to each other with very low levels of corresponding muscle activity. In contrast, sitting in an arched or slouched position could increase asymmetrical pressure on the disks, contributing to vertebral wedging, which could also contribute to spinal disk bulging and eventual back injury. The observations suggest that proper coaching may foster a stacksitting position of the spine, which could foster a healthier posture than slouched or arched spinal positions.