School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287, USA.
Department of Physical Education, Seoul National University, Seoul, 08826, Republic of Korea.
Sci Rep. 2019 Sep 4;9(1):12755. doi: 10.1038/s41598-019-49272-0.
Noticeable differences exist between treadmill and overground walking; kinematics, kinetics, and muscle activation patterns differ between the two. Many previous studies have attributed the differences to changes in visual information, air resistance, and psychological effects such as fear. In this study, we demonstrate that no treadmill serves as an inertial frame of reference. Considering the linear momentum principle, the finite sampling rate of the controller, and the limited power of the treadmill motor, we predict that 1) the error of the treadmill speed periodically varies depending on the locomotion phase and 2) this non-ideal behavior becomes more evident as the locomotion speed or the weight of the walker increases. Experimental observation confirmed our predictions by quantifying the variation of the actual treadmill belt speed and the ground reaction force in the anterior-posterior direction for different locomotion speeds and subject weights. These results emphasize a need for design criteria like the minimum sampling rate and the minimum motor power that treadmill locomotion studies should consider.
在跑步机和地面行走之间存在显著差异；两种运动方式的运动学、动力学和肌肉激活模式不同。许多先前的研究将这些差异归因于视觉信息、空气阻力和恐惧等心理效应的变化。在这项研究中，我们证明没有跑步机可以作为惯性参考系。考虑线性动量原理、控制器的有限采样率以及跑步机电机的有限功率，我们预测 1）跑步机速度的误差会根据运动阶段周期性变化，2）随着运动速度或步行者的重量增加，这种非理想行为变得更加明显。通过量化不同运动速度和受试者体重下实际跑步机履带速度和地面反作用力在前后方向上的变化，实验观察结果证实了我们的预测。这些结果强调了跑步机运动研究应该考虑的设计标准，如最小采样率和最小电机功率。
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