Mork Paul Jarle, Westgaard Rolf H
Department of Industrial Economics and Technology Management, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
Clin Biomech (Bristol). 2009 Feb;24(2):169-75. doi: 10.1016/j.clinbiomech.2008.11.001. Epub 2008 Dec 10.
Few studies have investigated sitting posture and low back muscle activity in occupational settings. This study aims to determine back posture and its influence on low back muscle activity in computer workers, and to investigate whether the work situation is associated with exacerbation of low back pain.
Twenty-one female computer workers participated. Surface electromyographic activity was recorded from lumbar multifidus, longissimus, and iliocostalis throughout the workday. Simultaneous inclinometer recordings from pelvis, upper trunk, and left thigh were used to determine back posture and identify periods with sitting, standing, and walking. Low back pain intensity was recorded by visual analogue scale every hour throughout the work and leisure periods.
All subjects adopted a markedly flexed back posture while seated at work. Surface electromyographic activity was very low for all muscles during sitting (group median <1.4% of root-mean-square-detected response at maximal voluntary contraction). Back posture moderately influenced electromyographic activity, accounting for 19% (sitting) to 38% (standing) of intra-individual variation in muscle activity. Subjects reporting aggravating low back pain (n=10) during the workday were not distinguished by duration of sitting, sitting posture, or low back muscle activity. Low back pain was markedly reduced from the last hour of work to the first hour of leisure, accompanied by an increase in low back muscle activity.
Low back muscle activity was very low during seated posture, presumably due to the flexion-relaxation phenomenon. Sustained stretch of passive lumbar structures in combination with essentially silent muscles may exacerbate low back pain in sedentary workers.
很少有研究在职业环境中调查坐姿和下背部肌肉活动。本研究旨在确定计算机工作者的背部姿势及其对下背部肌肉活动的影响，并调查工作情况是否与下背部疼痛加剧有关。
21名女性计算机工作者参与了研究。在整个工作日期间，记录腰方肌、竖脊肌和髂肋肌的表面肌电活动。同时使用来自骨盆、上躯干和左大腿的倾角计记录来确定背部姿势，并识别坐、站和行走的时间段。在工作和休闲期间，每小时通过视觉模拟量表记录下背部疼痛强度。
所有受试者在工作时坐着都采取明显的背部前屈姿势。坐着时所有肌肉的表面肌电活动都非常低（组中位数<最大自主收缩时均方根检测反应的1.4%）。背部姿势对肌电活动有适度影响，占个体肌肉活动变化的19%（坐着）至38%（站立）。在工作日报告下背部疼痛加重的受试者（n=10）在坐的持续时间、坐姿或下背部肌肉活动方面没有区别。从工作的最后一小时到休闲的第一小时，下背部疼痛明显减轻，同时下背部肌肉活动增加。
坐姿时下背部肌肉活动非常低，可能是由于屈曲放松现象。被动腰椎结构的持续拉伸与基本静止的肌肉相结合，可能会使久坐工作者的下背部疼痛加剧。
