Computation of temporal gait parameters.

This work addresses the lack of reliable wearable methods to assess walking gaits in underwater environments by evaluating the lateral hydrodynamic pressure exerted on lower limbs. Sixteen healthy adults were outfitted with waterproof wearable inertial and pressure sensors. Gait analysis was conducted on land in a motion analysis laboratory using an optoelectronic system as reference, and subsequently underwater in a rehabilitation swimming pool. Differences between the normalized land and underwater gaits were evaluated using temporal gait parameters, knee joint angles and the total water pressure on the lower limbs. The proposed method was validated against the optoelectronic system on land; gait events were identified with low bias (0.01s) using Bland-Altman plots for the stride time, and an acceptable error was observed when estimating the knee angle (10.96° RMSE, Bland-Altman bias -2.94°). The kinematic differences between the land and underwater environments were quantified, where it was observed that the temporal parameters increased by more than a factor of two underwater (pz = 67.69%). The major finding of this work is that the hydrodynamic pressure on the lower limbs may offer a new and more reliable parameter for underwater motion analysis as it provided a reduced intra-subject variability as compared to conventional gait parameters applied in land-based studies.本研究针对水下环境步行步态评估缺乏可靠可穿戴方法的问题，通过检测作用于下肢的侧向流体动压力开展相关研究。招募16名健康成年人，为其穿戴防水型可穿戴惯性与压力传感器。分别在运动分析实验室的陆地场景中，以光电运动捕捉系统（optoelectronic system）作为金标准开展步态分析，随后在康复游泳池的水下环境中重复实验流程。研究采用时域步态参数、膝关节角度以及下肢所受总水压力，对标准化后的陆地与水下步态差异进行评估。本研究提出的方法已在陆地场景下以光电运动捕捉系统为参照完成验证：通过Bland-Altman分析图（Bland-Altman plots）计算跨步时间时，步态事件识别偏差极低（0.01秒）；膝关节角度估算误差处于可接受范围（均方根误差RMSE为10.96°，Bland-Altman偏差为-2.94°）。本研究量化了陆地与水下环境间的运动学差异，结果显示水下场景下时域步态参数增幅超两倍（pz=67.69%）。本研究的核心发现为：相较于陆地研究中常规使用的步态参数，下肢所受流体动压力的受试者内部变异性更低，因此可作为水下运动分析的新型且更可靠的评估参数。