The relationship between plantar sensation and muscle onset during automatic postural responses in people with multiple sclerosis and healthy controls

•People with multiple sclerosis (PwMS) have impaired plantar sensation.•PwMS have delayed automatic postural responses (APRs) compared to controls.•Increased muscle onset latencies are related to plantar sensation in both groups.•MS has no moderating effect on the plantar sensation and APR relationship. Plantar sensation is critical for balance control in people with multiple sclerosis (PwMS). While previous research has described its impact on standing balance, the influence of plantar sensation during automatic postural responses (APRs) is not well understood in PwMS. The purpose of this study was to characterize the relationship between plantar sensation and APRs in PwMS and controls. A secondary aim was to determine whether the relationship between plantar sensation and APRs is different across PwMS and control groups. 122 PwMS and 48 age-matched controls underwent forward and backward support-surface perturbations from stance. The onset of the tibialis anterior (TA) and medial gastrocnemius (MG) were the primary reactive balance outcome measures for backward and forward losses of balance, respectively. Plantar sensation was measured as the vibration sensation threshold (VT). As expected, PwMS had significantly higher (i.e., worse) VT (p