Locomotor Apparatus Bioengineering Laboratory, Department of Human Movement and Sport Sciences, University of Rome Foro Italico, piazza Lauro de Bosis 15, 00135 Rome, Italy.
J Biomech. 2012 Apr 5;45(6):1123-6. doi: 10.1016/j.jbiomech.2011.12.020. Epub 2012 Feb 10.
The purpose of this study was to identify consistent features in the signals supplied by a single inertial measurement unit (IMU), or thereof derived, for the identification of foot-strike and foot-off instants of time and for the estimation of stance and stride duration during the maintenance phase of sprint running. Maximal sprint runs were performed on tartan tracks by five amateur and six elite athletes, and durations derived from the IMU data were validated using force platforms and a high-speed video camera, respectively, for the two groups. The IMU was positioned on the lower back trunk (L1 level) of each athlete. The magnitudes of the acceleration and angular velocity vectors measured by the IMU, as well as their wavelet-mediated first and second derivatives were computed, and features related to foot-strike and foot-off events sought. No consistent features were found on the acceleration signal or on its first and second derivatives. Conversely, the foot-strike and foot-off events could be identified from features exhibited by the second derivative of the angular velocity magnitude. An average absolute difference of 0.005 s was found between IMU and reference estimates, for both stance and stride duration and for both amateur and elite athletes. The 95% limits of agreement of this difference were less than 0.025 s. The results proved that a single, trunk-mounted IMU is suitable to estimate stance and stride duration during sprint running, providing the opportunity to collect information in the field, without constraining or limiting athletes' and coaches' activities.
本研究旨在确定单个惯性测量单元 (IMU) 或其衍生信号中存在的一致特征，用于识别跑步时的足触地和足离地时刻，并估计冲刺维持阶段的支撑和跨步持续时间。五位业余运动员和六位精英运动员在草皮跑道上进行了最大冲刺跑，来自 IMU 数据的持续时间分别使用力台和高速摄像机进行了验证，对于这两个组。IMU 被放置在每个运动员的下背部（L1 水平）。计算了 IMU 测量的加速度和角速度矢量的幅度以及它们的小波介导的一阶和二阶导数，并寻找与足触地和足离地事件相关的特征。在加速度信号或其一阶和二阶导数上没有发现一致的特征。相反，可以从角速度幅度的二阶导数显示的特征中识别出足触地和足离地事件。IMU 和参考估计值之间的平均绝对差异为 0.005 秒，适用于支撑和跨步持续时间以及业余和精英运动员。这种差异的 95%一致性界限小于 0.025 秒。结果证明，单个安装在躯干上的 IMU 适合估计冲刺跑中的支撑和跨步持续时间，从而有机会在不限制或限制运动员和教练活动的情况下在现场收集信息。
