BACKGROUND: Spinal manipulation has been shown to affect muscle activity, posture, and pain. To date, no studies have examined the effect of manipulation on biomechanical factors during sitting. Therefore, the purpose of this study was to investigate the immediate effect of lumbar spinal manipulation on trunk muscle activation, spine posture and movements, and perceived ratings of transient pain in asymptomatic adults during prolonged office sitting.
METHODS: Twenty healthy adults were recruited for a single laboratory session that included a standardized office sitting/data entry protocol (120 min total, 3 blocks of 40 min). Data were collected between July and August 2012. The first block (baseline) was immediately followed by two experimental blocks. Prior to the start of each experimental block, participants were transferred to a therapy plinth and placed side lying (right side down), and a random presentation of either a control or high velocity low amplitude thrust directed at L4/L5 was delivered. Continuous measures of muscle activity, spine posture, and spine movements were recorded throughout the sitting trials. Perceived transient pain was measured by visual analogue scale at 10-min intervals (including immediately before and after the randomized maneuvers).
RESULTS: There were no significant differences in spine or pelvic posture or perceived back pain following either the manipulation or control maneuvers. Significantly reduced muscle activity and increased shifts of the lumbar spine angle were identified in the block following manipulation compared to both baseline and post control blocks.
CONCLUSIONS: Spinal manipulation does not appear to have an immediate impact on spine or pelvic posture in healthy adults but does appear to reduce muscle activity and increase spine movement during sitting. Future work should replicate this study with a larger population in a field setting. It may be worthwhile to explore the implication of reduced muscle activation and increased spine movements during prolonged sitting for office workers that receive manipulations or mobilizations during their workday.
