Test-retest reliability and usability evaluation of a wearable plantar pressure monitoring system for linear and curved walking

Plantar pressure measurements provide critical insights into the structural and functional attributes of the lower limbs and feet. While previous studies have evaluated the reliability of insole technology for assessing foot pressure distribution during linear walking, natural motion often involves a combination of straight walking and turning. This study aimed to validate the test-retest reliability of a wearable in-shoe plantar pressure monitoring system for both linear and curved walking trajectories and to determine the minimum distance required to achieve excellent reliability for each output variable. Thirty-one healthy participants (15 females and 16 males aged 19-25 years) were recruited. Each participant performed two testing sessions, 4-7 days apart, involving three walking conditions: linear walking (LIN), clockwise curved walking (CW), and counterclockwise curved walking (CCW). A wearable footwear system equipped with embedded pressure sensors was used to collect plantar pressure data. Five key parameters-the peak pressure (PP), pressure‒time integral (PTI), full width at half maximum (FWHM), maximum pressure gradient (MaxPG), and average pressure (AP)-were analyzed across eight foot regions. Reliability was assessed via intraclass correlation coefficients (ICCs), Bland‒Altman plots, and minimal detectable changes (MDCs). Additionally, the System Usability Scale (SUS) and Intrinsic Motivation Inventory (IMI) were administered to evaluate usability. The wearable system demonstrated good reliability, with ICC values of approximately 0.9 for most parameters across all walking conditions. For whole-foot analysis, all variables presented ICCs > 0.60, confirming high reliability. The minimum distances required to achieve an ICC ≥ 0.90 were 207 m for LIN, 255 m for CW, and 467 m for CCW. The usability scores (SUS and IMI) indicated high user satisfaction and system acceptability. The developed wearable plantar pressure system exhibited excellent reliability and usability for both linear and curved walking conditions. These findings support its potential for clinical and research applications, particularly in scenarios involving mixed walking trajectories. The study also highlights the importance of considering step count thresholds to ensure reliable assessments in diverse walking conditions.