Sensorimotor Neuroscience Laboratory, Department of Kinesiology and MiNDS Neuroscience Institute, McMaster University, Hamilton, Ontario, Canada.
Gait Posture. 2011 Mar;33(3):423-8. doi: 10.1016/j.gaitpost.2010.12.016. Epub 2011 Feb 2.
This study examined lower extremity biomechanics during the initiation of stair descent from an upright, static posture. Seventeen healthy subjects (aged 23±2.4 years) descended a five-step, steel-reinforced, wooden laboratory staircase (34° decline). Ten trials of stair descent were separated into two blocks of five trials. Beginning from an upright posture, subjects descended the staircase at their preferred velocity (0.53±0.082 m/s) and continued the length of the laboratory walkway (∼4 m). Joint mechanics were contrasted between gait cycles. Relative to the initiation cycle at the top of the staircase, the dissipative knee extensor (K3) and hip flexor (H2) moments and powers were independent of progression velocity and approximated steady-state (i.e., constant) values after the first cycle of the trail limb (Step 5 to Step 3). In contrast, a salient relationship was observed between progression velocity and ankle joint mechanics at initial-contact. The plantiflexor moment, power and work at initial-contact (A1) increased with centre of mass velocity. Our results demonstrate that while the knee extensor moment is the primary dissipater of mechanical energy in stair descent, the ankle plantiflexors are the primary dissipaters associated with increased progression velocity. In addition, the results show that steady-state stair descent may not be attained during the first gait cycle of the trail limb. These data shed light on locomotive strategies used in stair descent and can be applied in biomechanical models of human stair gait. Researchers and practitioners should take into consideration the influence of gait cycle and progression velocity when evaluating lower extremity function in stair descent.
本研究考察了从直立静止姿势开始下楼梯时下肢的生物力学。17 名健康受试者（年龄 23±2.4 岁）下了一个五阶、钢加强的木制实验室楼梯（34°倾斜）。10 次楼梯下降试验分为两个 5 次试验组。受试者从直立姿势开始，以自己喜欢的速度（0.53±0.082 m/s）下降楼梯，并继续沿着实验室走道走（约 4 m）。关节力学在步态周期之间进行对比。与楼梯顶部的起始周期相比，消耗性膝关节伸肌（K3）和髋关节屈肌（H2）的力矩和功率与行进速度无关，并且在试验腿的第一周期（第 5 步到第 3 步）后接近稳态（即恒定）值。相比之下，在初始接触时观察到与踝关节力学之间存在显著的关系与进展速度。初始接触时的跖屈肌力矩、功率和功（A1）随质心速度的增加而增加。我们的结果表明，虽然膝关节伸肌力矩是楼梯下降中机械能的主要耗散者，但踝关节跖屈肌是与行进速度增加相关的主要耗散者。此外，结果表明，在试验腿的第一步态周期中可能无法达到稳态楼梯下降。这些数据阐明了楼梯下降中使用的运动策略，可以应用于人类楼梯步态的生物力学模型。研究人员和从业者在评估楼梯下降时应考虑步态周期和行进速度的影响。
