Identifying heel contact and toe-off using forceplate thresholds with a range of digital-filter cutoff frequencies
Identifying heel contact and toe-off using forceplate thresholds with a range of digital-filter cutoff frequencies
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DOI：
10.1123/jab.19.2.178
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发表时间：
2003-05-01
影响因子：
1.4
通讯作者：
Sparrow, WAT
中科院分区：
文献类型：
--
作者：
Tirosh, O;Sparrow, WAT
人类步态的分析需要精确测量脚-地面接触，通常使用脚-地面反作用力阈值或运动学数据来确定。本研究检查了在五个垂直力阈值上计算事件时间的差异，并验证了基于垂直加速度的算法作为脚跟接触和脚趾离地的测量。实验还揭示了使用一系列数字滤波器截止频率对原始位移/时间数据进行平滑处理时，确定足跟接触和脚趾离地的准确性。四名健康的年轻参与者完成了10次步行试验：5次以正常速度（1.2米/秒）和5次以快速速度（1.8尼特）。光电系统与测力板同步，测量垂直力超过（脚跟接触）或低于（脚趾离地）10、20、30、40和50 N的时间。然后将这些数据进行比较，并随后用于验证基于加速度的方法，该方法用于计算脚跟接触和脚趾离地，并在四个截止频率范围内过滤位移/时间数据。线性回归分析表明，在正常和快速行走，任何力的阈值在0至50 N可以用来预测脚跟接触时间。为了估计脚趾离地低力阈值，应使用10 N或更小。当用最佳截止频率过滤原始数据时，使用10-N阈值获得的测力板事件时间与使用基于加速度的算法获得的脚跟接触和脚趾离地事件时间之间的差异的绝对值（AbsDt）显示正常行走的平均AbsDt为10.0和16.5 ms，快速行走的平均AbsDt为7.4和13.5 ms。非最佳截止频率的数据平滑影响了算法计算的事件时间，并产生了更大的AbsDt值。因此，最佳的数据过滤程序是必不可少的，以确保脚跟接触和脚趾离地时，使用基于加速度的算法的准确测量。
Analysis of human gait requires accurate measurement of foot-ground contact, often determined using either foot-ground reaction force thresholds or kinematic data. This study examined the differences in calculating event times across five vertical force thresholds and validated a vertical acceleration-based algorithm as a measure of heel contact and toe-off. The experiment also revealed the accuracy in determining heel contact and toe-off when raw displacement/time data were smoothed using a range of digital filter cutoff frequencies. Four healthy young participants completed 10 walking trials: 5 at normal speed (1.2 m/s) and 5 at fast speed (1.8 nits). A 31) optoelectric system was synchronized with a forceplate to measure the times when vertical force exceeded (heel contact) or fell below (toe-off) 10, 20, 30, 40, and 50 N. These were then compared and subsequently used to validate an acceleration-based method for calculating heel contact and toe-off with the displacement/time data filtered across a range of four cutoff frequencies. Linear regression analyses showed that during both normal and fast walking, any force threshold within 0 to 50 N could be used to predict heel-contact time. For estimating toe-off low force thresholds, 10 N or less should be used. When raw data were filtered with the optimal cutoff frequency, the absolute value (AbsDt) of the difference between the forceplate event times obtained using a 10-N threshold and the event times of heel contact and toe-off using the acceleration-based algorithms revealed average AbsDt of 10.0 and 16.5 ms for normal walking, and 7.4 and 13.5 ms for fast walking. Data smoothing with the non-optimal cutoff frequencies influenced the event times computed by the algorithms and produced greater AbsDt values. Optimal data filtering procedures are, therefore, essential for ensuring accurate measures of heel contact and toe-off when using the acceleration-based algorithms.