Electrical Engineering Department, Campus of Gijon, University of Oviedo, 33204 Oviedo, Spain.
Sensors (Basel). 2023 Feb 24;23(5):2523. doi: 10.3390/s23052523.
Ground contact time (GCT) is one of the most relevant factors when assessing running performance in sports practice. In recent years, inertial measurement units (IMUs) have been widely used to automatically evaluate GCT, since they can be used in field conditions and are friendly and easy to wear devices. In this paper we describe the results of a systematic search, using the Web of Science, to assess what reliable options are available to GCT estimation using inertial sensors. Our analysis reveals that estimation of GCT from the upper body (upper back and upper arm) has rarely been addressed. Proper estimation of GCT from these locations could permit an extension of the analysis of running performance to the public, where users, especially vocational runners, usually wear pockets that are ideal to hold sensing devices fitted with inertial sensors (or even using their own cell phones for that purpose). Therefore, in the second part of the paper, an experimental study is described. Six subjects, both amateur and semi-elite runners, were recruited for the experiments, and ran on a treadmill at different paces to estimate GCT from inertial sensors placed at the foot (for validation purposes), the upper arm, and upper back. Initial and final foot contact events were identified in these signals to estimate the GCT per step, and compared to times estimated from an optical MOCAP (Optitrack), used as the ground truth. We found an average error in GCT estimation of 0.01 s in absolute value using the foot and the upper back IMU, and of 0.05 s using the upper arm IMU. Limits of agreement (LoA, 1.96 times the standard deviation) were [-0.01 s, 0.04 s], [-0.04 s, 0.02 s], and [0.0 s, 0.1 s] using the sensors on the foot, the upper back, and the upper arm, respectively.
地面接触时间（GCT）是评估运动表现时最重要的因素之一。近年来，惯性测量单元（IMU）已被广泛用于自动评估 GCT，因为它们可以在现场条件下使用，并且是友好且易于佩戴的设备。在本文中，我们描述了使用 Web of Science 进行系统搜索的结果，以评估使用惯性传感器进行 GCT 估计的可靠选项。我们的分析表明，从上身（上背部和上臂）估算 GCT 的情况很少。从这些位置正确估算 GCT 可以将跑步表现分析扩展到公众，在公众中，用户，特别是职业跑步者，通常会在口袋中佩戴理想的感应设备，这些口袋非常适合安装带有惯性传感器的感应设备（甚至可以为此目的使用自己的手机）。因此，在本文的第二部分，描述了一项实验研究。招募了六名受试者，包括业余和半精英跑步者，在不同的跑步机速度下进行实验，以从脚部（用于验证目的）、上臂和上背部放置的惯性传感器估算 GCT。在这些信号中识别初始和最终脚部接触事件，以估算每个步的 GCT，并与使用光学运动捕捉系统（Optitrack）作为地面真实值估算的时间进行比较。我们发现，使用脚部和上背部 IMU 估算 GCT 的平均误差为 0.01 秒，使用上臂 IMU 估算的平均误差为 0.05 秒。使用脚部、上背部和上臂上的传感器的一致性界限（LoA，标准偏差的 1.96 倍）分别为[-0.01 s，0.04 s]、[-0.04 s，0.02 s]和[0.0 s，0.1 s]。
