Objective: To understand and examine the relation between postural response latencies obtained during postural perturbations and representative measures of balance during standing (sway variables) and walking (trunk motion).

Design: Cross-sectional.

Setting: University medical center.

Participants: Persons with multiple sclerosis (MS) (n = 40) were compared with similar aged control subjects (n = 20). There were 20 subjects with MS in the normal walking velocity group and 20 subjects with MS who had slow walking velocity based on a timed 25-foot walk (T25FW) of < 5 seconds.

Interventions: None.

Main Outcome Measures: Postural response latency, sway variables, trunk motion variables.

Results: We found that subjects with MS with both slow or normal walking velocities had significantly longer postural response latencies than the healthy control group. Postural response latency was not correlated with the T25FW. Postural response latency was significantly correlated with center of pressure sway variables during quiet standing (root mean square: ρ = .334, P = .04; range: ρ = .385, P = .017; mean velocity: ρ = .337, P = .038; total sway area: ρ = .393, P = .015). Postural response latency was also significantly correlated with motion of the trunk during walking (sagittal plane range of motion: ρ = .316, P = .05; SD of transverse plane range of motion: ρ = -.43, P = .006).

Conclusions: These findings clearly indicate that slow postural responses to external perturbations in patients with MS contribute to disturbances in balance control during both standing and walking.