Plantar pressure variations during stair ascending and descending with and without load

Background: This experimental repeated-measures study investigated how carrying an additional load - symmetrically in a backpack or asymmetrically on one shoulder - affects plantar pressure distribution and contact time during stair ascent and descent. Methods: Twelve healthy adults performed six stair-walking conditions (ascent and descent, with and without load). Plantar pressure and contact time were recorded in ten foot regions using a pedobarographic plate. Non-parametric repeated-measures tests were applied (Friedman RM-ANOVA with Wilcoxon signed-rank post-hoc tests using Holm correction), and effect size was quantified using Kendall's W. Results: Plantar pressure differed significantly across foot regions in both tasks (ascent: χ ²(9) = 56.09, W = 0.623; descent: χ ²(9) = 58.01, W = 0.645; p < 10-6), confirming strong task-related heterogeneity. Rearfoot loading dominated ascent, while forefoot loading prevailed during descent. Load effects were modest and region-specific, with significant increases in Heel Medial and hallux under asymmetric load. Contact time also varied markedly across regions (ascent: W = 0.831; descent: W = 0.849), but load-related differences were not significant after Holm correction. Conclusions: Task strategy (ascent vs. descent) exerts a far greater influence on plantar loading patterns than a small additional load. Asymmetric carriage produces localized changes in PP but does not substantially alter contact time. This parameter may serve as a proxy for gait speed in future mixed-effects models.