Exploring the repeatability of curved gait during an instrumented figure of 8 walk test, a new methodology

There is currently no consensus on how to assess curved gait. One of the challenges is to define when a turn begins and ends. Two fundamental characteristics of a turn are the variation in gait speed and the vertical rotational rate of the pelvis. Our study aimed to assess the repeatability of an instrumented figure of eight walk test (F8Wi) by evaluating right and left turns over 3 sessions. Fourteen healthy participants were included. Participants walked barefoot and with shoes, both at comfortable and fast speed. Several points of interest were identified: the start of speed deceleration (A), the start of body rotation (B), the peak angular acceleration (C), the end of body rotation (D), the end of speed acceleration (E). The dependent variables were time intervals between AB, AC, AD, AE, BD, and gait parameters measured during the turn defined by time between A and E: mean sum load from the lumbar inertial measurement unit, mean sum load from the lumbar inertial measurement unit normalised by AE time and mean of the right knee maximum flexion of each step during the turn. The coefficient of variation (CV), standard error of measurement (SEM), minimum detectable change (MDC_95%), and 3D Bland‒Altman plot assessed repeatability. For all conditions, the CVs of time between AE, AD, and BD were less than 10%, whereas for times at AB, AC, AD, BD, the CVs were between 10% and 20%. The SEMs remained low for all variables and conditions, and the MDC95% was greater than the standard deviation. For the gait parameters, CVs were less than 10%, the SEMs remained low, and the MDC_95% was greater than the standard deviation. The protocol employed a combination of knee electrogoniometers, an IMU and a Doppler radar to evaluate curved walking during an F8Wi modified. Curved walking repeatable over time and under different gait conditions. This repeatability study shows that a more accessible setup could open the door to assessing curved walking.