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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 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.

Menz HB, Lord SR, St George R, Fitzpatrick RC. Walking stability and sensorimotor function in older people with diabetic peripheral neuropathy. Arch Phys Med Rehabil 2004;85:245–52. Objective To evaluate, in older people with diabetic peripheral neuropathy (DPN) and in age-matched controls, acceleration patterns of the head and pelvis when walking to determine the effect of lower-limb sensory loss on walking stability. Design Case-control study. Setting Falls and balance laboratory in Australia. Participants Thirty persons with diabetes mellitus (age range, 55–91y) and 30 age-matched controls. Interventions Acceleration patterns of the head and pelvis were measured while participants walked on a level surface and an irregular walkway. Participants also underwent tests of vision, sensation, strength, reaction time, and balance. Main outcome measures Temporospatial gait parameters and variables derived from acceleration signals. Results Participants with DPN had reduced walking speed, cadence, and step length, and less rhythmic acceleration patterns at the head and pelvis compared with controls. These differences were particularly evident when participants walked on the irregular surface. Participants with DPN also had impaired peripheral sensation, reaction time, and balance. Conclusions Older people with DPN have an impaired ability to stabilize their body when walking on irregular surfaces, even if they adopt a more conservative gait pattern. These results provide further insights into the role of peripheral sensory input in the control of gait stability, and suggest possible mechanisms underlying the increased risk of falling in older people with diabetic neuropathy.

King LA, St George RJ, Carlson-Kuhta P, Nutt JG, Horak FB. Preparation for compensatory forward stepping in Parkinson's disease. Objective To characterize preparation for compensatory stepping in people with Parkinson's disease (PD) compared with healthy control subjects, and to determine whether levodopa medication improves preparation or the execution phases of the step. Design Observational study. Setting Outpatient neuroscience laboratory. Participants Nineteen participants with idiopathic PD tested both in the on and off levodopa states and 17 healthy subjects. Intervention Moveable platform with posterior translations of 24cm at 56cm/s. Main Outcome Measures Compensatory steps forward, in response to a backward surface translation (24cm amplitude at 56cm/s), were categorized according to the presence of an anticipatory postural adjustment (APA) before stepping: no APA, single APA, or multiple APAs. The following step parameters were calculated: step latency, step length, center of mass (CoM) average velocity, and CoM displacement at the step initiation. Results Lateral APAs were evident in 57% and 42% of trials for people with PD in the off and on medication states, respectively, compared with only 10% of trials for control subjects. Compared with subjects with PD who did not have APAs, those subjects with PD who did make an APA prior to stepping had significantly later (mean ± SEM, 356±16ms vs 305±8ms) and shorter (mean ± SEM, 251±27mm vs 300±16mm) steps, their CoM was significantly farther forward (185±7mm vs 171±5mm) at foot-off, and they took significantly more steps to regain equilibrium. Levodopa did not affect the preparation or execution phase of compensatory stepping. Poor axial scores and reports of freezing in the United Parkinson's Disease Rating Scale were associated with use of 1 or more APAs before compensatory stepping. Conclusions Lateral postural preparation prior to compensatory stepping in subjects with PD was associated with inefficient balance recovery from external perturbations.