Relationship Between Anterior–Posterior Plantar Reaction Force Distribution and Gait Speed in Post-Stroke Patients

Background: Gait speed is an important indicator of walking ability in post-stroke patients. Although gait speed is associated with anterior–posterior reaction force (AP RF), how AP RF is distributed across the plantar surface and whether this distribution is associated with gait speed remain unclear. Methods: Fifteen post-stroke patients and 18 healthy controls were included. AP RF was measured during walking using a sensor shoe system equipped with four triaxial force sensors located at the heel, first metatarsal (MT1), fifth metatarsal (MT5), and toe regions. AP RF distribution was quantified as the relative contribution of each plantar region and compared among the paretic, non-paretic, and control sides across the stance phase using linear mixed-effects models. Associations between AP RF distribution and gait speed were examined using Spearman’s rank correlation coefficients, with p-values adjusted for multiple testing using the Benjamini–Hochberg false discovery rate procedure. Results: Significant group × stance phase interactions were observed for the relative contributions of MT1 and MT5. After correction for multiple comparisons, the MT1 contribution at 81–90% of the stance phase was lower on both the paretic and non-paretic sides than on the control side, whereas the MT5 contribution at 1–10% was higher on both sides than on the control side. Total AP RF was also lower on the paretic and/or non-paretic sides than on the control side during several stance phases. On the non-paretic side, the MT5 contribution at 1–10% was negatively correlated with gait speed (rs = −0.66, BH-FDR adjusted p = 0.04). Conclusions: Post-stroke patients showed altered AP RF distribution during the early and late stance phases compared with healthy controls. Greater MT5 contribution on the non-paretic side during early stance was associated with slower gait speed, suggesting that AP RF distribution may provide additional information for characterizing gait impairment after stroke beyond total AP RF.