<b>A validation study of a low-cost foot-mounted IMU system for gait assessment</b>

Numerous commercial foot-mounted Inertial Measurement Units (IMUs) like RunScribe^TM and S-TAG are used for real-world gait analysis. These IMUs utilize manufacturer-specific algorithms to offer metrics for performance and injury prevention. Compared to the RunScribe^TM, which has been widely validated and applied, the S-TAG is a newer, more affordable system whose accuracy has not been completely evaluated prior to its use. Hence, this study evaluates the validity and reliability of S-TAG for gait assessment in overground walking and running. Fourteen participants equipped with the S-TAG and RunScribe^TM and performed a 10-meter walk/run test (10 MW/RT) at self-selected speeds. Data were also collected using the laboratory system (LAB) with an optical motion capture system (OptiTrack) with force plates (Kistler) simultaneously. Pearson’s r and intraclass correlation coefficients (ICCs) revealed moderate to excellent agreement (0.73-0.96 and 0.70-0.98, respectively) between the S-TAG and LAB, and overground walking and running trials demonstrated moderate to excellent reliability (ICC = 0.71-0.91, CV = 1.6-18.0%), revealing to be reliable. The S-TAG effectively measures walking and running gait parameters in healthy adults. More importantly, the gait measurement performance of the S-TAG is comparable to that of RunScribe^TM and superior in some aspects, highlighting the potential for cost-effective real-world gait analysis.This research was funded by the National Natural Science Foundation of China, grant number 72071018; the Engineering Research Center of Strength and Conditioning Training Key Core Technology Integrated System and Equipment, Ministry of Education, grant number 2024GCZX001; and the National Key R&amp;D Program of China, grant number 2020YFF0304702.多款商用足部穿戴式惯性测量单元（Inertial Measurement Unit, IMU），如RunScribe™与S-TAG，被应用于真实场景步态分析。此类IMU搭载厂商专属算法，可输出用于运动表现评估与运动损伤预防的相关指标。相较于已得到广泛验证与应用的RunScribe™，S-TAG是一款更新型、成本更低廉的系统，但其在投入使用前并未完成全面的精度评估。因此，本研究针对S-TAG在平地行走与跑步的步态评估中的有效性与可靠性展开验证。14名受试者分别穿戴S-TAG与RunScribe™设备，以自选速度完成10米行走/跑步测试（10 MW/RT）。同时，借助搭载测力台（Kistler）的光学动作捕捉系统（OptiTrack）搭建的实验室系统（LAB）采集同步数据。皮尔逊相关系数（Pearson’s r）与组内相关系数（intraclass correlation coefficient, ICC）结果显示，S-TAG与LAB系统间的一致性处于中等至极佳水平（相关系数分别为0.73~0.96与0.70~0.98）；平地行走与跑步测试的步态数据则表现出中等至极佳的重测可靠性（ICC=0.71~0.91，变异系数CV=1.6%~18.0%），证明其具备可靠的测量性能。S-TAG可有效测量健康成年人的行走与跑步步态参数。更为关键的是，S-TAG的步态测量性能可与RunScribe™媲美，且在部分维度上更具优势，凸显了其用于低成本真实场景步态分析的应用潜力。本研究受国家自然科学基金（项目编号：72071018）、教育部体能训练关键核心技术集成系统与装备工程研究中心（项目编号：2024GCZX001）以及国家重点研发计划（项目编号：2020YFF0304702）资助。