Gallagher S
National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, Pennsylvania, USA.
Spine (Phila Pa 1976). 1997 Aug 15;22(16):1864-72. doi: 10.1097/00007632-199708150-00011.
A split-plot experimental design was used to evaluate the influence of posture, trunk angle, and rotational velocity on peak torque output and myoelectric activity during maximal trunk extension maneuvers.
To determine whether the kneeling posture alters extension torque capabilities in isometric and isokinetic exercises as compared with standing. Also, to ascertain whether recruitment of trunk muscles is modified by such a postural change.
Factors such as workplace geometry may force workers to adopt awkward or unusual postures in the performance of manual tasks. An understanding of the limitations placed on strength in unconventional working postures is crucial to the proper design of jobs.
Twenty-one healthy male subjects (mean age = 36 years +/- 7 SD) performed 12 trunk extension exertions in standing and kneeling postures. Isometric tests were performed at 22.5 degrees, 45 degrees, and 67.5 degrees of trunk flexion. Isokinetic tests were done at three velocities: 30 degrees/sec, 60 degrees/sec, and 90 degrees/sec. Electromyographic data were collected from eight trunk muscles to assess muscle recruitment under each condition. A priori orthogonal contrasts were specified for analysis of both torque and electromyographic data.
The kneeling posture was associated with a 15% decrease in peak torque output when contrasted with standing: however, no concomitant change in trunk muscle activity was evident. Trunk hyperflexion (isometric tests) and increasing rotational velocity (isokinetic tests) were associated with reduced torque in both postures. Trunk muscle activity was primarily affected by changes in trunk angle and velocity of contraction.
A reduced extensor capability exists in the kneeling posture, despite equivalent trunk muscle activity. The similar activation patterns in both postures suggest that the strength deficit does not result from alterations in trunk muscle function. Rather, it may be the consequence of a reduced capability to rotate the pelvis in the kneeling posture, due to a disruption of the biomechanical linkage of the leg structures.
采用裂区实验设计来评估姿势、躯干角度和旋转速度对最大躯干伸展动作中峰值扭矩输出和肌电活动的影响。
确定与站立相比，跪姿是否会改变等长和等速运动中的伸展扭矩能力。此外，确定这种姿势变化是否会改变躯干肌肉的募集情况。
工作场所几何形状等因素可能迫使工人在执行体力任务时采取笨拙或不寻常的姿势。了解非常规工作姿势下力量的限制对于正确设计工作至关重要。
21名健康男性受试者（平均年龄 = 36岁±7标准差）以站立和跪姿进行12次躯干伸展用力。在躯干屈曲22.5度、45度和67.5度时进行等长测试。以三种速度进行等速测试：30度/秒、60度/秒和90度/秒。从八块躯干肌肉收集肌电数据，以评估每种情况下的肌肉募集情况。指定先验正交对比用于分析扭矩和肌电数据。
与站立相比，跪姿时峰值扭矩输出降低了15%；然而，躯干肌肉活动没有明显的相应变化。两种姿势下，躯干过度屈曲（等长测试）和旋转速度增加（等速测试）均与扭矩降低有关。躯干肌肉活动主要受躯干角度和收缩速度变化的影响。
尽管躯干肌肉活动相当，但跪姿时伸肌能力降低。两种姿势下相似的激活模式表明，力量不足并非由躯干肌肉功能改变所致。相反，这可能是由于腿部结构生物力学联系中断，导致跪姿时骨盆旋转能力降低的结果。
