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Abstract: 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. [Copyright &y& Elsevier]

Abstract: Objective: To test a proposed mechanism for the effect of balance-based torso-weighting (BBTW) in people with multiple sclerosis (MS) and healthy controls. The mechanism to be tested is that application of light weights to the trunk may result in a biomechanical shift of postural sway in the direction of weighting, mechanically facilitating maintenance of the center of mass over the base of support. Design: Nonrandomized controlled trial. Setting: Motion analysis laboratory. Participants: Participants with MS (n=20; average Expanded Disability Status Scale score, 4.1) and controls matched for sex, age, height, and weight (n=18). Intervention: Light weights strategically placed according to the BBTW protocol were applied to all participants after at least 3 walking trials and 10 seconds of quiet standing with feet together and eyes open and then eyes closed. Measures were repeated after weighting. Main Outcome Measure: Forceplate center of pressure (COP) changes >1 standard error of measurement. Results: With BBTW, people with MS had larger maximum changes in COP than healthy controls in the left-right direction but not in the anterior-posterior direction. COP changes >1 standard error of measurement occurred in the same direction of weighting 20% of the time (95% confidence interval, 5–34), ranging from 10% to 28% across conditions and directions of postural sway. Direction of greatest weight placement did not match the direction of change in the average COP in most participants with MS or the healthy controls in eyes open or eyes closed conditions (P<.001). Conclusions: If BBTW worked via a biomechanical shift of the center of mass, COP changes should match the direction of greatest weighting with BBTW. Our data allowed us to reject this hypothesis. Future research may explore alternative mechanisms of action underlying this intervention. [Copyright &y& Elsevier]

Abstract: Objective: To examine the psychometric properties (test-retest reliability, concurrent validity, construct validity) of the Balance Rehabilitation Unit (BRU) during testing of sensory integration processes in healthy adults and individuals with vestibular disorders. Design: Experimental cross-sectional design. Setting: Clinic. Participants: Participants (N=90) included 30 subjects with vestibular disorders (age range, 18–85y), 30 young healthy adults (age range, 18–50y), and 30 older healthy adults (age range, 60–85y). Interventions: Not applicable. Main Outcome Measures: Participants were tested twice with the BRU and once with the SMART EquiTest Sensory Organization Test (SOT). The center of pressure (COP) in the anteroposterior direction (COPap) and the COP in the mediolateral direction (COPml) were recorded. The COPap and COPml time series were used to estimate the area and velocity of the COP. Results: The intraclass correlation coefficient of the COP area and velocity measures for the BRU for all subjects was at least .76 in all sensory organization conditions (P<.001). Significant correlations were found between the BRU and the SOT, ranging from .64 to .81 for COP area and from .44 to .76 for COP velocity. The older control group had significantly greater COP area and velocity compared with younger controls for the BRU and the SOT. The COP (area, velocity) was significantly higher for the younger individuals in the vestibular group than the younger controls. Conclusions: The reliability and validity of COP measurements obtained during testing of the sensory integration processes were demonstrated using the BRU. Future work should examine the responsiveness of these measures when individuals with balance disorders participate in rehabilitation. [Copyright &y& Elsevier]

Abstract: Objective: To determine the foot pressure pattern of individuals with medial knee osteoarthritis (OA) and to analyze its relation with knee flexion/extension range of motion. Design: Descriptive. Setting: Rehabilitation center. Participants: Individuals with unilateral, painful medial knee OA (n=50; mean age, 75y; OA group) were enrolled as subjects, and young, healthy persons (n=50; mean age, 28y; young group) and elderly persons (n=44; mean age, 74y; elderly group) without any pain, deformity, or apparent OA changes in either knee were enrolled as controls. Intervention: Walking 10m at a comfortable speed. Main Outcome Measures: Partial foot pressures as percentages of body weight (%PFP), anteroposterior length of the center of pressure (COP) path as a percentage of foot length (%Long), transverse width of the COP path as a percentage of foot width (%Trans), knee flexion/extension range of motion (in the OA group). Results: The %PFP values for the heel and hallux, %Long, and %Trans were all significantly lower in the OA group than in controls (P<.001, all). Within the OA group, a limited range of knee extension was significantly associated with a short %Long (P<.001) but not with %Trans. Conclusions: Individuals with medial knee OA exhibited low pressure on the heel and hallux and short %Long of the COP path, and limitation of knee extension was associated with shortness of %Long. The shortness of %Long in the OA group likely resulted from insufficient knee extension during the heel-contact phase associated with low pressure on the heel. %Long is a useful parameter in gait analysis by using a foot pressure measurement system. [Copyright &y& Elsevier]

Abstract: Objectives: To examine the stepping performance during voluntary and waist-pull perturbation-induced step initiation in people with chronic stroke. Design: Repeated-measures single-case design. Setting: University-based research laboratory. Participants: Community-dwelling stroke survivors (N=10). Interventions: Not applicable. Main Outcome Measures: Ground reaction forces and kinematic data were recorded to assess anticipatory postural adjustments (APAs) and step characteristics for both voluntary and induced stepping conditions. Results: Induced stepping was performed with both the paretic (35% trials) and nonparetic legs (65% trials). Induced first steps occurred earlier and were executed faster than rapid voluntary steps. Compared with voluntary stepping, induced first step APAs were shorter in duration. Step height was higher with the nonparetic leg for both stepping conditions. Use of the paretic leg increased (52%) during the diagonal perturbations that passively unloaded the stepping limb compared with the use of the paretic leg (33%) for forward perturbations. Conclusions: The results indicated differences in executing voluntary and induced stepping, and between the paretic and nonparetic limbs in individuals with chronic stroke. The findings suggested guidelines for using stepping as a component of neurorehabilitation programs for enhancing balance and mobility. Additional larger-scale studies remain to be undertaken to further investigate these issues. [Copyright &y& Elsevier]

Abstract: Objective: To determine whether a 12-week whole-body vibration (WBV) training program improved balance in participants with type 2 diabetes mellitus (T2DM). Design: Randomized controlled trial. Setting: Primary health care setting. Participants: Participants with T2DM (N=50). Interventions: Participants were randomly allocated to either a WBV group (n=25), which performed a 12-week WBV-based exercise program on an oscillating platform (12–16Hz—4mm; 3 sessions/wk), or a usual-care control group (n=25). Main Outcome Measures: Clinical and sociodemographic variables were recorded at baseline. Static balance and dynamic balance were also assessed at baseline by measuring postural sway (measurement of center of pressure [COP] excursions in the anteroposterior and mediolateral directions) using a Wii Balance Board and the Timed Up and Go test. Results: Significant between-group differences in COP excursions with participants' eyes closed were found with their feet apart and feet together. In addition, participants in the WBV group exhibited significantly lower COP excursions with their eyes closed after the intervention, while participants in the control group experienced a nonsignificant deterioration in COP excursions (ie, greater excursion) with their eyes open (mediolateral axis). There was no significant difference in the Timed Up and Go test values postintervention. Conclusions: WBV provides a safe and well-tolerated approach to improve balance in participants with T2DM. These findings may have important implications for falls prevention in those with T2DM in the primary health care setting. [Copyright &y& Elsevier]

Abstract: Objective: To investigate seated postural control in persons with spinal cord injury (SCI) compared with age-matched controls. Design: Cohort. Setting: University research laboratory. Participants: Adults (N=36; mean age ± SD, 22.5±3.2y): 7 persons with high SCI (HI group; injury level greater than T10), 11 persons with low SCI (LI group; injury level between T10 and L4), and 18 persons with non-SCI. Intervention: Not applicable. Main Outcomes Measures: Participants sat on a force platform on a custom-built wooden box with their arms by their side. Postural control was quantified in several ways. Participants completed a functional reach test. The amount of postural sway was quantified by characterizing the center of pressure (COP) trajectory by determining median velocity and root mean square of the signal. In addition, the virtual time to contact to the functional boundary was quantified. Last, the instability index was determined as the ratio of the COP area to the functional boundary. Results: There were no group differences in COP-based metrics (P>.05). There was no difference between SCI groups in functional reach (P>.05). The HI group had a smaller virtual time to contact (VTC) than the control group (.50±.20s vs .98±.24s, P<.05). Both SCI groups had a greater instability index than the control group, with the HI group having the largest amount of instability (P<.05). Conclusions: The observations suggest that VTC analysis is appropriate to investigate seated postural control. It is proposed that including VTC of seated postural control as an outcome measure will provide novel information concerning the effectiveness of various rehabilitation approaches and/or technologies aimed at improving seated postural control in persons with SCI. [Copyright &y& Elsevier]

Abstract: Objectives: To establish (1) the intrarater and interrater reliability of Four Square Step Test (FSST) times in persons with chronic stroke; (2) the concurrent validity of FSST times with standing balance and functional mobility measures; and (3) the FSST cutoff score for distinguishing the differences in dynamic balance performance of persons with chronic stroke from healthy control adults. Design: Cross-sectional study. Setting: University-based rehabilitation center. Participants: Convenience sample of subjects (N=30) consisting of community-dwelling persons with chronic stroke (n=15) and healthy control adults (n=15). Interventions: Not applicable. Main Outcome Measures: FSST scores; balance and functional mobility measured using Berg Balance Scale (BBS) scores; Timed Up & Go (TUG) test scores; and limits of stability (LOS) measured by dynamic posturography. Results: FSST times showed good intrarater reliability, with intraclass correlation coefficients ranging from .82 to .83 and an interrater reliability >.99. An FSST cutoff score of 11 seconds was able to discriminate between healthy adults older than 50 years and persons with stroke (sensitivity, 73.3%; specificity, 93.3%). FSST times were correlated with LOS scores for directional control in the backward direction (r=.64; P=.01). FSST was approaching a significant correlation with TUG scores (r=.59; P=.02) and LOS scores for endpoint excursion in the forward direction (r=−.58; P=.02). However, there was no correlation with BBS scores. Conclusion: FSST is an easy-to-administer clinical test with good intrarater and interrater reliability in persons with chronic stroke to assess dynamic standing balance. FSST times of 11 seconds are able to differentiate between persons with chronic stroke and healthy adults older than 50 years. The correlation of FSST times with standing balance and functional mobility measures requires further research with a larger sample size. [Copyright &y& Elsevier]