de Looze M P, Toussaint H M, van Dieën J H, Kemper H C
Department of Health Science, Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
J Biomech. 1993 Sep;26(9):1067-76. doi: 10.1016/s0021-9290(05)80006-5.
The mechanical loading on the body during the act of lifting has been estimated frequently. The opposite act of lowering has received much less attention. The aim of the present study was to compare the mechanical loading of the musculoskeletal system in lifting and lowering. Eight subjects repetitively lifted and lowered a load, using two different techniques (a leg and a back technique). The ankle, knee, hip and lumbosacral joint moments were estimated and the myoelectrical (EMG) activity of seven (leg and back) muscles was recorded. The differences between the lifting and lowering phase for the leg technique were similar to those observed when the back technique was applied. The joint moment curves in lifting showed a high level of agreement with the (time-reversed) moment curves in lowering. Peak moments in lowering were only slightly lower than in lifting (peak lumbar moments were 5.4% lower). These small differences were related to different acceleration profiles at the centre of gravity of the body/load complex. The EMG activity was considerably lower in lowering than in lifting. The mean EMG in lowering (average for seven muscles) was only about 69% of the EMG in lifting. This was attributed to the different types of muscle actions involved in lifting (mainly concentric) and lowering (mainly eccentric). Furthermore, the EMG results suggest that similar inter-muscular coordination is involved in lowering and lifting. The results give rise to the assumption that in lifting and lowering similar muscle forces are produced to meet the (nearly) equal joint moments, but in lowering these forces are distributed over a smaller cross-sectional area of active muscle, which might imply a higher risk of injury.
人们经常对举重过程中身体所承受的机械负荷进行估算。而与之相反的放下动作却很少受到关注。本研究的目的是比较举重和放下过程中肌肉骨骼系统的机械负荷。八名受试者使用两种不同的技术（腿部技术和背部技术）反复进行举重和放下负荷的动作。估算了踝关节、膝关节、髋关节和腰骶关节的力矩，并记录了七块（腿部和背部）肌肉的肌电（EMG）活动。腿部技术在举重和放下阶段的差异与应用背部技术时观察到的差异相似。举重时的关节力矩曲线与放下时（时间反转）的力矩曲线高度一致。放下时的峰值力矩仅略低于举重时（腰椎峰值力矩低5.4%）。这些微小差异与身体/负荷复合体重心处不同的加速度分布有关。放下时的肌电活动明显低于举重时。放下时的平均肌电（七块肌肉的平均值）仅约为举重时肌电的69%。这归因于举重（主要是向心收缩）和放下（主要是离心收缩）所涉及的不同类型的肌肉动作。此外，肌电结果表明，放下和举重过程中涉及相似的肌肉间协调。研究结果引发了这样一种假设，即在举重和放下过程中会产生相似的肌肉力量来满足（几乎）相等的关节力矩，但在放下时，这些力量分布在较小的活跃肌肉横截面积上，这可能意味着更高的受伤风险。
