Commissaris D A, Toussaint H M
Amsterdam Spine Unit, Vrije Universiteit, The Netherlands.
Ergonomics. 1997 May;40(5):559-75. doi: 10.1080/001401397188035.
This study investigated the effect of the presence or absence of load knowledge on the low-back loading and the control of balance in lifting tasks. Low-back loading was quantified by the net sagittal plane torque at the lumbo-sacral joint. The control of balance was studied by the position of the centre of gravity relative to the base of support, the horizontal and vertical momentum of the centre of gravity and the angular momentum of the whole body. In a first experiment, 8 male subjects lifted a rather heavy load (22% of body mass), using a leglift and a backlift, while they were familiar with the load mass. To counteract the threat to balance, imposed by picking up a load in front of the body, the subjects performed specific preparations, based upon the known load mass; prior to load pick-up, profound changes in the horizontal and angular momentum were found. The preparations were technique specific. Preserving balance seemed easier while picking up a load with a backlift than with a leglift. In the second experiment, 25 male subjects lifted a 6 kg box, which they expected to be 16 kg, because, in a series of lifts, the load mass was changed from 16 to 6 kg without their knowledge. Despite the 10 kg difference in actual load mass, the net torque at the lumbo-sacral joint was not different between lifting 6 and 16 kg, until 150 ms after box lift-off. Moreover, lifting of the overestimated load mass caused a disturbance of balance in 92% of the trials. The postural reactions aimed at regaining balance were not accompanied by an increased low-back loading. It was concluded that the absence of load knowledge, and the following overestimation of the load mass to be lifted, lead to an increased mechanical load on the lumbar spine and to an increased risk of losing balance in lifting tasks. Both events may contribute to a higher risk of low-back injury in manual materials handling tasks.
本研究调查了有无负荷知识对提举任务中腰部负荷及平衡控制的影响。腰部负荷通过腰骶关节矢状面净扭矩来量化。通过重心相对于支撑面的位置、重心的水平和垂直动量以及全身的角动量来研究平衡控制。在第一个实验中，8名男性受试者在熟悉负荷质量的情况下，采用腿举和背举方式提起相当重的负荷（体重的22%）。为了抵消在身体前方提起负荷对平衡造成的威胁，受试者根据已知的负荷质量进行了特定准备；在提起负荷之前，发现水平和角动量有显著变化。这些准备是特定技术的。背举提起负荷时保持平衡似乎比腿举更容易。在第二个实验中，25名男性受试者提起一个6千克的箱子，他们预计箱子重16千克，因为在一系列提举过程中，负荷质量在他们不知情的情况下从16千克变为6千克。尽管实际负荷质量相差10千克，但在箱子提起后150毫秒之前，提起6千克和16千克负荷时腰骶关节的净扭矩并无差异。此外，提起被高估的负荷质量在92%的试验中导致了平衡干扰。旨在恢复平衡的姿势反应并未伴随着腰部负荷增加。研究得出结论，缺乏负荷知识以及随后对要提起的负荷质量的高估，会导致腰椎机械负荷增加以及提举任务中失去平衡的风险增加。这两个因素都可能导致手工搬运任务中腰部受伤的风险更高。
