Schmidt M W, López-Ortiz C, Barrett P S, Rogers L M, Gruben K G
Biomedical Engineering Department, University of Wisconsin-Madison, 2000 Observatory Dr., 1081 Gym/Natatorium, Madison, WI 53706, USA.
Exp Brain Res. 2003 May;150(2):245-54. doi: 10.1007/s00221-003-1462-0. Epub 2003 Apr 8.
The abilities of a kinematic model and a muscle model of the human lower limb to predict the stereotyped direction of the muscular component of foot force produced by seated subjects in a static task were tested and compared. Human subjects ( n=11) performed a quasi-static, lower-limb pushing task against an instrumented bicycle pedal, free to rotate about its own axis, but with the crank fixed. Each pushing trial consisted of applying a force from the resting level to a force magnitude target with the right foot. Ten force target magnitudes were used (200, 250, ..., 650 N) along with 12 pedal positions. For each pushing effort, the muscular contribution to the measured foot force was determined from push onset to peak attained force. This segment was well characterized by a straight line across subjects, pedal positions, and force target magnitudes. The linear nature of the muscular component allowed a characteristic direction to be determined for each trial. A three-joint (hip, knee, and ankle) and a two-joint (hip and knee) net joint torque optimization was applied to a sagittal-plane kinematic model to predict the characteristic force direction. A musculoskeletal model was also used to create a feasible force space (FFS) for the lower limb. This FFS represents the range of possible forces the lower limb could theoretically produce. From this FFS, the direction of the maximum feasible foot force was determined and compared with the characteristic direction of subject performance. The muscle model proved to be the most effective in predicting subject force direction, followed by the three-joint and two-joint net joint torques optimizations. Similarities between the predictions of the kinematic and muscle model were also found.
测试并比较了人体下肢运动学模型和肌肉模型预测静态任务中坐着的受试者产生的足部力量肌肉成分的刻板方向的能力。11名人类受试者对一个装有仪器的自行车踏板进行了准静态下肢推压任务，该踏板可绕自身轴自由旋转，但曲柄固定。每次推压试验包括用右脚从静止水平施加力到力大小目标。使用了10个力目标大小（200、250、……、650牛）以及12个踏板位置。对于每次推压努力，从推压开始到达到峰值力确定肌肉对测量到的足部力量的贡献。该部分在受试者、踏板位置和力目标大小之间表现为一条直线。肌肉成分的线性性质使得可以为每次试验确定一个特征方向。将一个三关节（髋、膝和踝）和一个两关节（髋和膝）净关节扭矩优化应用于矢状面运动学模型，以预测特征力方向。还使用了一个肌肉骨骼模型来创建下肢的可行力空间（FFS）。这个FFS代表了下肢理论上可以产生的可能力的范围。从这个FFS中，确定最大可行足部力量的方向并与受试者表现的特征方向进行比较。结果证明肌肉模型在预测受试者力量方向方面最有效，其次是三关节和两关节净关节扭矩优化。还发现了运动学模型和肌肉模型预测之间的相似性。
