Gagnon M, Smyth G
Department of Physical Education, University of Montreal, P.Q., Canada.
J Biomech. 1991;24(3-4):191-203. doi: 10.1016/0021-9290(91)90177-o.
The problem of injuries in manual materials handling remains a big concern in industrialized countries. It has become imperative in occupational biomechanics to extend the analyses to all pertinent factors involved in working tasks and to adopt an experimental approach leading to the understanding of the relative demands imposed simultaneously on all body joints. The evaluation of joint muscular work and the processes of energy generation, absorption and transfer appears promising as a tool in the detection of risk factors in working tasks. The present study consisted of evaluating two tasks (lifting and lowering) performed at five different heights (from 15 to 185 cm) with five different loads (from 3.3 to 22.0 kg). The subjects were eight experienced workers from a food product warehouse. Cinematography techniques and two AMTI force platforms were used to collect the data. Dynamic and planar segmental analyses were performed to calculate the net muscular moments at the joints, and work was calculated from the integration of muscular power. Factorial analyses of variance with repeated measures were performed on the dependent variables to evaluate the main effects of tasks, loads, and heights (for lifting and for lowering) and the interactions. The results revealed the adoption of different movement strategies in the handling of heavier loads. In the first, a larger emphasis of energy transfer and movement economy; in the second, a reduction in the relative contribution of the shoulders to the detriment of an increased participation of the lower back and hips was found. The comparison between lifting and lowering tasks indicated that lifting was only slightly more demanding than lowering for maximum muscular moments (about 15%) but much more so for mechanical work (about 40%); however, the nature of the efforts in eccentric contractions suggests that the lowering of heavy loads may be risky. Finally, the results revealed the deviation of height of handling from the waist level to be a significant factor. Handling at lower heights was considerably more demanding but the work was shared by several joints, mainly by the hips and lower back (about 70%); on the other hand, in handling above the waist, the work efforts were concentrated on the upper limbs (about 80%). In most cases, the participation of lower limbs was minimal and some movement strategies are suggested for future research.
在工业化国家，人工搬运物料时的受伤问题仍是一个重大关切。在职业生物力学领域，将分析扩展到工作任务中涉及的所有相关因素，并采用一种能让人理解同时施加于所有身体关节的相对需求的实验方法，已变得势在必行。对关节肌肉工作以及能量产生、吸收和转移过程的评估，作为检测工作任务中风险因素的一种工具，似乎很有前景。本研究包括评估在五个不同高度（从15厘米到185厘米）下，使用五种不同负荷（从3.3千克到22.0千克）执行的两项任务（提起和放下）。受试者是来自一家食品仓库的八名经验丰富的工人。使用摄影技术和两个AMTI力平台来收集数据。进行动态和平面节段分析以计算关节处的净肌肉力矩，并通过肌肉功率积分来计算功。对因变量进行重复测量的方差分析，以评估任务、负荷和高度（对于提起和放下）的主要影响以及相互作用。结果显示在搬运较重负荷时采用了不同的运动策略。第一种情况是更强调能量转移和运动经济性；第二种情况是发现肩部的相对贡献减少，而下背部和臀部的参与增加。提起和放下任务之间的比较表明，对于最大肌肉力矩，提起仅比放下略具挑战性（约15%），但对于机械功则要高得多（约40%）；然而，离心收缩时用力的性质表明，放下重物可能有风险。最后，结果表明搬运高度偏离腰部水平是一个重要因素。在较低高度进行搬运要求高得多，但工作由多个关节分担，主要是臀部和下背部（约70%）；另一方面，在腰部以上进行搬运时，工作用力集中在上肢（约80%）。在大多数情况下，下肢的参与最小，并为未来研究提出了一些运动策略。
