Brian C Nairn1, Nadia R Azar, Janessa D M Drake. 1. School of Kinesiology & Health Science, Faculty of Health, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada.
Abstract
BACKGROUND: Sitting is a commonly adopted posture during work and prolonged exposures may have detrimental effects. Little attention has been paid to the thoracic spine and/or multiple axes of motion during prolonged sitting. Accordingly, this study examined three-dimensional motion and muscle activity of the trunk during two hours of uninterrupted sitting. METHODS: Ten asymptomatic males sat during a simulated office task. Kinematics were analyzed from six segments (Neck, Upper-, Mid-, and Lower-thoracic, Lumbar, and Pelvis) and electromyography was recorded from eight muscles bilaterally. RESULTS: Four participants developed transient pain. These participants showed higher average muscle activations in the abdominal muscles. Additionally, the non-pain group showed less lateral bend positional change in the mid-thoracic region compared to the upper- and lower-thoracic regions. Weak-to-moderate positive correlations were also found between rated pain and low back muscle activation. DISCUSSION: The results provided further evidence of reduced movement in non-pain developers and altered muscle activation patterns in pain developers. Low-level, prolonged static contractions could lead to an increased risk of injury; and though the increased abdominal activity in the pain developers was not directly associated with increased rated pain scores, this could indicate a pre-disposition to, or enhancer of, transient pain development.
BACKGROUND: Sitting is a commonly adopted posture during work and prolonged exposures may have detrimental effects. Little attention has been paid to the thoracic spine and/or multiple axes of motion during prolonged sitting. Accordingly, this study examined three-dimensional motion and muscle activity of the trunk during two hours of uninterrupted sitting. METHODS: Ten asymptomatic males sat during a simulated office task. Kinematics were analyzed from six segments (Neck, Upper-, Mid-, and Lower-thoracic, Lumbar, and Pelvis) and electromyography was recorded from eight muscles bilaterally. RESULTS: Four participants developed transient pain. These participants showed higher average muscle activations in the abdominal muscles. Additionally, the non-pain group showed less lateral bend positional change in the mid-thoracic region compared to the upper- and lower-thoracic regions. Weak-to-moderate positive correlations were also found between rated pain and low back muscle activation. DISCUSSION: The results provided further evidence of reduced movement in non-pain developers and altered muscle activation patterns in pain developers. Low-level, prolonged static contractions could lead to an increased risk of injury; and though the increased abdominal activity in the pain developers was not directly associated with increased rated pain scores, this could indicate a pre-disposition to, or enhancer of, transient pain development.