Smart rubber sensor repeatability and between-system agreement for peak plantar pressure in healthy and older adults during standing and walking

Smart Rubber technology enables a low-cost, platform-based approach to clinical plantar pressure monitoring, yet its metrological properties relative to established in-shoe sensors remain uncharacterised. We evaluated the within-session repeatability of a Smart Rubber platform sensor (SR Soft Vision) and its agreement with an established in-shoe resistive sensor array (F-Scan) during quiet standing and walking in 20 healthy adults and 10 ambulatory older adults receiving low-level long-term care support. Repeatability was assessed using intraclass correlation coefficients [ICC(A,1) and ICC(A, k)] with 95% confidence intervals, standard error of measurement (SEM), minimal detectable change (MDC95), and coefficient of variation. Between-system agreement was evaluated using Lin’s concordance correlation coefficient (CCC) and Bland–Altman analysis, while Pearson’s r was additionally reported as an index of linear association. During standing, directly calculated ICC(A,3) values for SR Soft Vision ranged from 0.974 to 0.993, and during walking they ranged from 0.952 to 0.989. Between-system agreement was task- and region-dependent: forefoot walking peak plantar pressure (PPP) showed near-zero concordance (CCC = 0.04) with large systematic bias (− 497 to − 528 kPa), persisting after exclusion of ceiling-attainment cases (sensitivity analysis). These findings demonstrate high within-session repeatability of SR Soft Vision and support its potential use for repeated within-device assessment under a consistent protocol, while indicating that absolute PPP values are not interchangeable with F-Scan during dynamic forefoot loading.