Department of Mechanical Engineering, The University of Texas at Austin, TX 78712, USA.
Gait Posture. 2011 Apr;33(4):562-7. doi: 10.1016/j.gaitpost.2011.01.010. Epub 2011 Feb 26.
The ability to accelerate and decelerate is important for daily activities and likely more demanding than maintaining a steady-state walking speed. Walking speed is modulated by anterior-posterior (AP) ground reaction force (GRF) impulses. The purpose of this study was to investigate AP impulses across a wide range of speeds during accelerated and decelerated walking. Kinematic and GRF data were collected from 10 healthy subjects walking on an instrumented treadmill. Subjects completed trials at steady-state speeds and at four rates of acceleration and deceleration across a speed range of 0-1.8 m/s. Mixed regression models were generated to predict AP impulses, step length and frequency from speed, and joint moment impulses from AP impulses during non-steady-state walking. Braking and propulsive impulses were positively related to speed. The braking impulse had a greater relationship with speed than the propulsive impulse, suggesting that subjects modulate the braking impulse more than the propulsive impulse to change speed. Hip and knee extensor, and ankle plantarflexor moment impulses were positively related to the braking impulse, and knee flexor and ankle plantarflexor moment impulses were positively related to the propulsive impulse. Step length and frequency increased with speed and were near the subjects' preferred combination at steady-state speeds, at which metabolic cost is minimized in nondisabled walking. Thus, these variables may be modulated to minimize metabolic cost while accelerating and decelerating. The outcomes of this work provide the foundation to investigate motor coordination in pathological subjects in response to the increased task demands of non-steady-state walking.
加速和减速的能力对于日常活动很重要，而且可能比维持稳定的步行速度要求更高。步行速度是通过前后（AP）地面反作用力（GRF）脉冲来调节的。本研究的目的是在加速和减速行走过程中研究整个速度范围内的 AP 脉冲。运动学和 GRF 数据是从在仪器化跑步机上行走的 10 名健康受试者中收集的。受试者在稳态速度和四个加速度和减速度下完成试验，速度范围为 0-1.8 m/s。混合回归模型用于预测 AP 脉冲、步长和频率与速度的关系，以及非稳态行走时关节力矩脉冲与 AP 脉冲的关系。制动和推进脉冲与速度呈正相关。制动脉冲与速度的关系大于推进脉冲，这表明受试者通过调节制动脉冲而不是推进脉冲来改变速度。髋关节和膝关节伸肌以及踝关节跖屈肌力矩脉冲与制动脉冲呈正相关，而膝关节屈肌和踝关节跖屈肌力矩脉冲与推进脉冲呈正相关。步长和频率随速度增加，且在稳态速度下接近受试者的最佳组合，在非残疾行走中，代谢成本最小化。因此，这些变量可能会被调节以最小化代谢成本，同时加速和减速。这项工作的结果为研究病理受试者在非稳态行走增加的任务要求下的运动协调提供了基础。
