Intra-session repeatability, turning laterality, and turning patterns during the instrumented figure-of-eight walk test

Abstract The figure-of-eight walk test (F8W) is a key component of the functional assessment of curved gait. A new instrumented methodology (F8Wi), combining a lumbar inertial measurement unit (IMU) and Doppler radar, has demonstrated good test-retest repeatability over time. However, the intra-session repeatability has not yet been investigated. Moreover, the literature remains contradictory regarding differences between right and left turns. Therefore, this study had two objectives: to evaluate the intra-session repeatability of a F8Wi protocol and to compare differences in turning time and gait parameters according to turning laterality, trial number, and walking condition. Twenty-two participants completed a F8Wi test comprising four loops, including four left turns and four right turns. The test was performed under four conditions: shod at a comfortable (SC) and fast (SF) speed, and barefoot at a comfortable (BC) and fast (BF) speed. Several points of interest were identified with a Doppler radar and an inertial measurement unit (IMU): the start of speed deceleration (A), the start of body rotation (B), the peak angular acceleration (C), the end of body rotation (D), and the end of speed acceleration (E). The dependent variables were time intervals between AB, AD, AE, BD, and gait parameters measured during the turn defined by AE time: gait cadence, mean step and cycle time (left and right). The intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimal detectable change (MDC 95% ), and coefficient of variation (CV) assessed repeatability. ANOVAs and post hoc analyses were conducted to examine the main effects and interactions of turn laterality (left vs. right), trial number (1–8), and condition. The F8Wi test demonstrated good intra-session repeatability (on average: ICC = 0.85 and CV = 16.5%). However, the first and final turns were less repeatable and differed significantly from the other turns ( p < 0.05). In contrast to the effect of walking condition, turn laterality had little influence. The F8Wi is a reliable functional assessment tool that needs to be explored in clinical assessment, particularly for evaluating turning asymmetries in timing and gait parameters. However, the first and final turns involve a distinct timing compared with the others. Walking conditions can also be adjusted to introduce different task constraints.