Postural Response Latencies Are Related to Balance Control During Standing and Walking in Patients With Multiple Sclerosis

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.     

A Primary Care–Based Randomized Controlled Trial of 12-Week Whole-Body Vibration for Balance Improvement in Type 2 Diabetes Mellitus

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.     

Postural balance under normal and altered sensory conditions in normal-weight and overweight children

Background

Little or no research has been done in the overweight child on the relative contribution of multisensory information to maintain postural stability. Therefore, the purpose of this study was to investigate postural balance control under normal and experimentally altered sensory conditions in normal-weight versus overweight children.

Methods

Sixty children were stratified into a younger (7–9 yr) and an older age group (10–12 yr). Participants were also classified as normal-weight (n = 22) or overweight (n = 38), according to the international BMI cut-off points for children. Postural stability was assessed during quiet bilateral stance in four sensory conditions (eyes open or closed, normal or reduced plantar sensation), using a Kistler force plate to quantify COP dynamics. Coefficients of variation were calculated as well to describe intra-individual variability.

Findings

Removal of vision resulted in systematically higher amounts of postural sway, but no significant BMI group differences were demonstrated across sensory conditions. However, under normal conditions lower plantar cutaneous sensation was associated with higher COP velocities and maximal excursion of the COP in the medial-lateral direction for the overweight group. Regardless of condition, higher variability was shown in the overweight children within the 7–9 yr old subgroup for postural sway velocity, and more specifically medial–lateral velocity.

Interpretation

In spite of these subtle differences, results did not establish any clear underlying sensory organization impairments that may affect standing balance performance in overweight children compared to normal-weight peers. Consequently, it is believed that other factors account for overweight children's functional balance deficiencies.     

Multiple Sclerosis and Postural Control: The Role of Spasticity

Sosnoff JJ, Shin S, Motl RW. Multiple sclerosis and postural control: the role of spasticity.

Objectives

To examine the association between spasticity and postural control in subjects with multiple sclerosis (MS).

Design

Cross-sectional.

Setting

Motor control laboratory.

Participants

Subjects with MS (n=16, 2 male) and age and sex-matched subjects (n=16) participated in the investigation. All subjects with MS had Expanded Disability Status Scale scores between 0 and 4.5 and modified Ashworth scale scores between 1 and 3.

Interventions

Not applicable.

Main Outcome Measures

Postural control was measured with a force platform that quantifies ground reaction forces and moments in mediolateral and anteroposterior directions. Postural control was indexed with anterior-posterior sway range, medial-lateral sway range, 95% elliptical area of the deviations of center of pressure (COP), velocity of COP sway, and the frequency at which 95% of spectral profile was contained. Participants with MS further underwent assessment of the soleus Hoffman reflex (H-reflex) as an index of spasticity.

Results

Cluster analysis on H-reflex data identified groups of MS participants with high spasticity (n=7) and low spasticity (n=9). There were no differences in age, duration of MS, and disease severity between MS groups. There were no differences in anterior-posterior sway range between any of the groups. The high spasticity group had greater COP area, velocity, and mediolateral sway compared with the low spasticity and control group, and the low spasticity group had postural control values between the high spasticity and control groups.

Conclusions

The pattern of results suggests that spasticity contributes to postural deficits observed in MS.     

The influence of an auditory-memory attention-demanding task on postural control in blind persons

Background

In order to evaluate the effect of an auditory–memory attention-demanding task on balance control, nine blind adults were compared to nine age–gender-matched sighted controls. This issue is particularly relevant for the blind population in which functional assessment of postural control has to be revealed through “real life” motor and cognitive function. The study aimed to explore whether an auditory–memory attention-demanding cognitive task would influence postural control in blind persons and compare this with blindfolded sighted persons.

Methods

Subjects were instructed to minimize body sway during narrow base upright standing on a single force platform under two conditions: 1) standing still (single task); 2) as in 1) while performing an auditory–memory attention-demanding cognitive task (dual task). Subjects in both groups were required to stand blindfolded with their eyes closed. Center of Pressure displacement data were collected and analyzed using summary statistics and stabilogram-diffusion analysis.

Findings

Blind and sighted subjects had similar postural sway in eyes closed condition. However, for dual compared to single task, sighted subjects show significant decrease in postural sway while blind subjects did not.

Interpretation

The auditory–memory attention-demanding cognitive task had no interference effect on balance control on blind subjects. It seems that sighted individuals used auditory cues to compensate for momentary loss of vision, whereas blind subjects did not. This may suggest that blind and sighted people use different sensorimotor strategies to achieve stability.     

Peripheral neuropathy may not be the only fundamental reason explaining increased sway in diabetic individuals

Background

Individuals with diabetic neuropathy sway more than control individuals while standing. This review specifically evaluated whether peripheral sensory neuropathy can be the only fundamental reason accounting for significant increased sway within this population.

Methods

Twenty-six experimental articles were selected using MEDLINE and reference lists of relevant articles. The articles chosen investigated kinematic data of postural behaviour in controls and individuals with diabetic neuropathy during stance. Results of literature were compared with four expectations related to the peripheral sensory neuropathy fundamental hypothesis.

Findings

Consistent with the peripheral sensory neuropathy hypothesis, the literature showed that individuals with diabetic neuropathy sway more than controls in quiet stance and even more so if their visual or vestibular systems were perturbed. Inconsistent with the hypothesis, individuals with diabetic neuropathy are more destabilised than controls in conditions altering sensation of the feet and legs (standing on a sway-referenced surface).

Interpretation

The review showed that the peripheral sensory neuropathy hypothesis may not be the only fundamental cause accounting for significant increased postural sway in individuals with diabetic neuropathy. Visual impairments and changes in postural coordination may explain the divergence between expectations and results. In order to develop interventions aimed at improving postural control in individuals with diabetic neuropathy, scientific exploration of these new expectations should be detailed. Also at the practical level, the review discussed which additional sensory information – at the level of the hands and feet – may be more beneficial in individuals with diabetic neuropathy to reduce their postural sway.     

Spinal Cord Injury and Time to Instability in Seated Posture

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.     

Comparative Impacts of Tai Chi,Balance Training,and a Specially-Designed Yoga Program on Balance in Older Fallers

Objective

To compare the effect of a custom-designed yoga program with 2 other balance training programs.

Design

Randomized controlled trial.

Setting

Research laboratory.

Participants

A group of older adults (N=39; mean age, 74.15±6.99y) with a history of falling.

Interventions

Three different exercise interventions (Tai Chi, standard balance training, yoga) were given for 12 weeks.

Main Outcome Measures

Balance performance was examined during pre- and posttest using field tests, including the 8-foot up-and-go test, 1-leg stance, functional reach, and usual and maximal walking speed. The static and dynamic balances were also assessed by postural sway and dynamic posturography, respectively.

Results

Training produced significant improvements in all field tests (P<.005), but group difference and time × group interaction were not detected. For postural sway, significant decreases in the area of the center of pressure with eyes open (P=.001) and eyes closed (P=.002) were detected after training. For eyes open, maximum medial-lateral velocity significantly decreased for the sample (P=.013). For eyes closed, medial-lateral displacement decreased for Tai Chi (P<.01). For dynamic posturography, significant improvements in overall score (P=.001), time on the test (P=.006), and 2 linear measures in lateral (P=.001) and anterior-posterior (P<.001) directions were seen for the sample.

Conclusions

Yoga was as effective as Tai Chi and standard balance training for improving postural stability and may offer an alternative to more traditional programs.     

Age-Related Hip Proprioception Declines: Effects on Postural Sway and Dynamic Balance

Objective

To evaluate the effects of age on hip proprioception, and determine whether age-related hip proprioception declines disrupt balance.

Design

Survey of proprioception and balance differences between 3 age groups.

Setting

University balance laboratory.

Participants

Volunteer sample of independent community-dwelling adults (N=102) without sensory or other neurologic impairments in 3 age groups: younger (mean age, 24.6y; range, 19–37y), mid-aged (mean age, 53.3y; range, 40–64y), and older adults (mean age, 76.3y; range, 65–94y).

Interventions

Not applicable.

Main Outcome Measures

Hip joint position sense (JPS) and kinesthesia were measured using a custom-built device. JPS error was determined by the magnitude of matching errors during vision and no-vision conditions. Kinesthesia was evaluated by the ability to detect passive limb rotation without vision. Postural sway was assessed during static stance and measured using root mean square of center of pressure (COP) displacement and velocity of COP displacement. Clinical balance and fear of falling were assessed with the mini-Balance Evaluation Systems Test (mini-BESTest) and Activities-specific Balance Confidence Scale, respectively.

Results

Both older and mid-aged adults had significantly increased JPS error compared with younger adults (P<.05). Kinesthesia accuracy was significantly decreased in older adults compared with mid-aged and younger adults (P≤.01). Both measures of proprioception error correlated with age (P≤.001). There were no relationships between hip proprioception error and postural sway during static stance. However, older adults with lower proprioceptive error had significantly higher mini-BESTest scores of dynamic balance abilities (P=.005).

Conclusions

These results provide evidence of significant hip proprioception declines with age. Although these declines are not related to increases in postural sway, participants with hip proprioception declines demonstrated disrupted dynamic balance, as indicated by decreased mini-BESTest scores.     

Postural control is altered in patients with ankylosing spondylitis

Background

Ankylosing spondylitis is a chronic inflammatory disorder that can lead to increased axial and peripheral joint stiffness, impairing joint mobility. Impaired axial mobility due to vertebral ankylosis may result in changes in standing postural control. Little research has addressed changes in standing postural control in the ankylosing spondylitis population, nor how these issues might affect clinical understanding and treatment.

Methods

Sixteen ankylosing spondylitis patients, and 17 healthy controls participated. Each individual completed two 120-second quiet standing trials with eyes open and eyes closed, while standing upon two force platforms. Net center of pressure displacement and mean power frequency in the frontal and sagittal planes were calculated. A Spearman's rank correlation analysis was performed between net center of pressure measures and several clinical measures of disease activity.

Findings

Frontal plane net center of pressure displacement and frequency content, and sagittal plane net center of pressure displacement were significantly greater within the ankylosing spondylitis patient group. Ankylosing spondylitis patients demonstrated a significant increase in frontal plane net center of pressure displacement in the eyes-closed condition. Net center of pressure displacement and frequency were significantly correlated to the Bath Ankylosing Spondylitis Functional Index, and individual components of the Bath Ankylosing Spondylitis Metrology Index.

Interpretation

Quiet standing postural control was altered particularly so in the frontal plane in patients with ankylosing spondylitis, which may be associated with increased fall risk. Posturographic measures of postural control may serve as valuable clinical tools for the monitoring of disease progression and disease status in ankylosing spondylitis.     

A retrospective analysis of balance control parameters in elderly fallers and non-fallers

Background

A cross-sectional retrospective study of parameters reflecting balance function in elderly fallers and non-fallers was conducted to better understand postural control mechanisms in individuals prone to falls.

Methods

Ninety-nine old adults (65–91 years, mean age 78.4 (SD 5.7)) from two self-care residential facilities participated in the study. Foot center-of-pressure (CoP) displacement data were collected during narrow base upright stance eyes closed conditions and analyzed using summary statistics and Stabilogram-Diffusion Analysis (SDA) for mediolateral (ML) and anteroposterior (AP) directions. Subjects were instructed to minimize body sway.

Findings

Twenty-nine of the subjects reported at least one fall and 69 subjects reported no falls in the past six months. The SDA showed significantly higher short-term diffusion coefficients and critical displacements in fallers in the ML but not the AP direction. Mean sway area and ML-CoP sway range were also larger in fallers.

Interpretation

The greater ML critical displacement seen in fallers suggests that balance corrections on average occurred at higher sway amplitudes in this population. This is consistent with an ML decrease in the sensitivity of their postural control system. A higher short-term diffusion coefficient is consistent with increased muscle stiffness, a possible compensation for lost control sensitivity. Testing balance function under narrow stance conditions provides a modest increase in task difficulty that may help reveal pre-conditions of the balance control system that could increase the risk of falls.     

The effects of sandals on postural stability in patients with rheumatoid arthritis: An exploratory study

Background

Rheumatoid arthritis results in postural instability, pain and functional limitations. As rheumatoid arthritis progresses, localised forefoot deformities such as hallux valgus and clawing of the lesser toes occur, leading to a high proportion of people with rheumatoid arthritis wearing sandals. Sandals may affect postural stability due to poor motion control. The aim was to assess two different open-toe sandals on postural stability in people with rheumatoid arthritis.

Methods

Twenty women with rheumatoid arthritis were assessed in quiet standing under four conditions: (1) open-back sandal; (2) closed-back sandal; (3) own footwear and (4) bare feet. Postural stability was assessed as postural sway in the anterior-posterior and medial-lateral directions, with eyes open and eyes closed, using a pressure mat. Repeated measures analysis of variance tested the interaction effect of the footwear and eye conditions on anterior-posterior and medial-lateral sway.

Findings

In eyes-open, there was no significant difference in anterior–posterior sway (P = .169) and medial-lateral sway (P = .325) for footwear conditions. In eyes-closed testing, compared with barefoot conditions, increased anterior–posterior sway was observed with participants' footwear (P < .0001), the open-back sandal (P = .005), and the closed-back sandal (P = .017). With eyes closed, increased anterior–posterior sway was also observed with the participants' footwear compared with the closed-back sandal (P = .041). Increased medial-lateral sway was observed with the closed-back sandal compared with bare feet (P = .014).

Interpretation

Sandals may be detrimental to older women with well-established rheumatoid arthritis when eyes are closed. Further investigation is needed to evaluate the effect of sandals on dynamic tasks.     

Effects of vision and arm position on amplitude of arm postural tremor in patients with multiple sclerosis

Feys P, Helsen WF, Liu X, Lavrysen A, Nuttin B, Ketelaer P. Effects of vision and arm position on amplitude of arm postural tremor in patients with multiple sclerosis. Arch Phys Med Rehabil 2004;85:1031-3.

Objectives

To quantify the effects of vision and arm position on arm postural tremor, comparisons were made between flexed and extended arm positions performed with the eyes open and closed.

Design

Case-control study.

Setting

National multiple sclerosis (MS) center in Belgium.

Participants

Sixteen patients (32 arms) with MS who had intention tremor and 16 healthy controls (32 arms).

Interventions

Not applicable.

Main outcome measure

The amplitude of postural tremor was assessed by a magnetic position sensor attached to the index finger.

Results

The amplitude of postural tremor was not influenced by changes in visual condition or different arm positions. Both healthy controls and MS patients made more directional changes in the flexed, compared with the extended arm position.

Conclusions

The amplitude of the arm postural tremor in MS is independent of vision and arm position. Selecting 1 arm position is sufficient to assess postural tremor amplitude.     

Nonlinear analysis of sitting postural sway indicates developmental delay in infants

Background

Upright sitting is one of the first developmental motor milestones achieved by infants, and sitting postural sway provides a window into the developing motor control system. A variety of posture sway measures can be used, but the optimal measures for infant development have not been identified.

Methods

We have collected sitting postural sway data from two groups of infants, one with typical development (n = 33), and one with delayed development and either diagnosed with or at risk for cerebral palsy (n = 26), when the infants had developed to the point where they could just maintain sitting for about 10 s. Postural sway data was collected while infants were sitting on a force platform, and the center of pressure was analyzed using both linear and nonlinear measures.

Findings

Our results showed that a nonlinear measure, the largest Lyapunov exponent, was the only parameter of postural sway that revealed significant differences between infants with typical versus delayed development. The largest Lyapunov exponent was found to be higher for typically developing infants, indicating less repeated patterning in their movement coordination.

Interpretations

A nonlinear measure such as largest Lyapunov exponent may be useful as an identifier of pathology and as a yardstick for the success of therapeutic interventions.     

The evaluation of walking footwear on postural stability in healthy older adults: an exploratory study

Background

It has been proposed that walking footwear enhances postural stability in healthy older adults. The aim of the study is to evaluate differences between two different types of athletic footwear in relation to postural stability in healthy older adults.

Methods

A convenience sample of 21 healthy older adults with mean (SD) of 74 (5) years was recruited. Postural stability was measured using a force plate for anterior–posterior (AP) and mediolateral (ML) centre of pressure excursion for 30 s with eyes closed and open using two different types of athletic footwear. Each participant performed three repetitions of bipedal standing. Two-way analysis of variance tested the interaction effect of the footwear and eye conditions on anterior–posterior (AP) and mediolateral (ML) postural sway.

Findings

There was no significant footwear–eye condition interaction for anterior-posterior(AP) postural sway but there were significant main effects for both the footwear and eye conditions (P < 0.05). The significant main effects for the footwear conditions occurred between barefeet and the two shoe conditions, but not between the two shoe conditions. For mediolateral (ML) postural sway there was no significant interaction effect and no main effects for the footwear and eye conditions (P > 0.05).

Interpretation

The results suggest that older adults demonstrate an initial destabilisation effect which could possibly be of benefit to functional ability but the long-term effects of ability of athletic footwear to enhance postural stability requires further investigation.     

Estimating Postural Control With the Balance Rehabilitation Unit: Measurement Consistency,Accuracy, Validity,and Comparison With Dynamic Posturography

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 (COP_ap) and the COP in the mediolateral direction (COP_ml) were recorded. The COP_ap and COP_ml 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.     

Voluntary sway and rapid orthogonal transitions of voluntary sway in young adults,and low and high fall-risk older adults

Background

Falls amongst older people have been linked to reduced postural stability and slowed movement responses. The objective of this study was to examine differences in postural stability and the speed of response between young adults, low fall-risk older adults, and high fall-risk older adults during voluntary postural sway movements.

Methods

Twenty-five young adults (25 ± 4 years), and 32 low fall-risk (74 ± 5 years), and 16 high fall-risk (79 ± 7 years) older adults performed voluntary sway and rapid orthogonal transitions of voluntary sway between the anterior–posterior and medial–lateral directions. Measures included reaction and movement time and the amplitudes of the centre of pressure, centre of mass, and the separation distance between the centre of pressure and centre of mass.

Findings

Both fall-risk groups compared to the young had slower reaction and movement time, greater centre of pressure and/or centre of mass amplitude in the orthogonal (non-target) direction during voluntary sway, and reduced anterior–posterior and medial–lateral separation between the centre of pressure and centre of mass during voluntary sway and orthogonal transitions. High compared to low fall-risk individuals had slower reaction and movement time, increased non-target centre of mass amplitude during voluntary sway, and reduced medial–lateral centre of pressure and centre of mass separation during voluntary sway and orthogonal transitions.

Interpretation

Age-related deterioration of postural control resulted in slower reactive responses and reduced control of the direction of body movement during voluntary sway and orthogonal transitions. Slower postural reaction and movement time and reduced medial–lateral control of the centre of mass during voluntary sway movements are associated with increased fall-risk in community-living older people.     

Neuropsychological,Balance, and Mobility Risk Factors for Falls in People With Multiple Sclerosis: A Prospective Cohort Study

Objectives

To determine whether impaired performance in a range of vision, proprioception, neuropsychological, balance, and mobility tests and pain and fatigue are associated with falls in people with multiple sclerosis (PwMS).

Design

Prospective cohort study with 6-month follow-up.

Setting

A multiple sclerosis (MS) physiotherapy clinic.

Participants

Community-dwelling people (N=210; age range, 21–74y) with MS (Disease Steps 0–5).

Interventions

Not applicable.

Main Outcome Measures

Incidence of falls during 6 months' follow-up.

Results

In the 6-month follow-up period, 83 participants (39.7%) experienced no falls, 57 (27.3%) fell once or twice, and 69 (33.0%) fell 3 or more times. Frequent falling (≥3) was associated with increased postural sway (eyes open and closed), poor leaning balance (as assessed with the coordinated stability task), slow choice stepping reaction time, reduced walking speed, reduced executive functioning (as assessed with the difference between Trail Making Test Part B and Trail Making Test Part A), reduced fine motor control (performance on the 9-Hole Peg Test [9-HPT]), and reported leg pain. Increased sway with the eyes closed, poor coordinated stability, and reduced performance in the 9-HPT were identified as variables that significantly and independently discriminated between frequent fallers and nonfrequent fallers (model χ²₃=30.1, P<.001). The area under the receiver operating characteristic curve for this model was .712 (95% confidence interval, .638–.785).

Conclusions

The study reveals important balance, coordination, and cognitive determinants of falls in PwMS. These should assist the development of effective strategies for prevention of falls in this high-risk group.     

Effects of Age and Gender on Dynamic Stability During Stair Descent

Objective

To determine the effects of age and sex and their interaction effects on dynamic postural stability during stair descent.

Design

Cross sectional.

Setting

Laboratory.

Participants

Healthy younger adults (N=28) and healthy older adults (N=21).

Interventions

Not applicable.

Main Outcome Measures

Spatiotemporal gait parameters, displacement of center of mass (COM), instantaneous velocity of the COM, divergence between vertical projection of the COM, and center of pressure (COP).

Results

Interaction effects of age and sex were found in stride duration, COM displacement, and instantaneous velocity of the COM in the mediolateral direction. Older adults demonstrated longer stride duration with shorter double-limb stance and longer single-limb stance during stair descent. Women have significantly longer stride duration than men. The effects of sex and age were significant in the data normalized by height. Older adults and women demonstrated larger peak-to-peak COM displacement, peak instantaneous velocity of the COM, and COM-COP divergence than the younger individuals and men, respectively. Peak instantaneous velocity of the COM was significant different in most pairwise comparisons, but the COM-COP divergence was significantly different in several comparisons.

Conclusions

This study examined the COM and COP parameters to quantify dynamic stability during stair descent across sex and age. Although older women descended stairs successfully, they demonstrated differences in control of instantaneous velocity of the COM compared with the other participants. Dynamic instability could be detected by examining the control of instantaneous velocity of the COM. In developing a better understanding of the balance control of stair descent in healthy older adults, aging patients with various pathologies can be better assessed, appropriately treated, and provided with proper assistive devices.     

Reliability of Center of Pressure Measures for Assessing the Development of Sitting Postural Control

Kyvelidou A, Harbourne RT, Stuberg WA, Sun J, Stergiou N. Reliability of center of pressure measures for assessing the development of sitting postural control.

Objectives

To determine the reliability of linear and nonlinear tools, including intrasession and intersession reliability, when used to analyze the center of pressure (COP) time series during the development of infant sitting postural control.

Design

Longitudinal study.

Setting

University hospital laboratory.

Participants

Typically developing infants (N=33; mean ± SD age at entry in the study, 152.4±17.6d).

Interventions

Not applicable.

Main Outcome Measures

Infants were tested twice in 1 week at each of the 4 months of the study. Sitting COP data were recorded for 3 trials at each session (2 each month within 1 week). The linear COP parameters of root mean square and range of sway for both the anterior-posterior and the medial-lateral directions, and the sway path, were calculated. The nonlinear parameters of approximate entropy, Lyapunov exponent, and correlation dimension for both directions were also calculated. Intrasession and intersession reliability was quantified by the intraclass correlation coefficient (ICC).

Results

The nonlinear tool of approximate entropy presented high intrasession and intersession ICC values compared with all other parameters evaluated. Generally, intrasession and intersession reliability increased in the last 2 months of the data collection and as sitting posture matured.

Conclusions

Our results showed that the evaluation of COP data is a reliable method of investigating the development of sitting postural control. The present study emphasizes the need for establishing COP reliability before using it as a method of examining intervention progress directed at improving the sitting postural abilities in infants with motor developmental delays.