Impaired Postural Stability Research Articles

Effects of persistent Mal de debarquement syndrome on balance, psychological traits, and motor cortex exctiability

Mal de debarquement syndrome (MdDS) is a poorly characterized and understood disorder of perceived motion. We sought to characterize postural control and the psychological impact of MdDS. Additionally, we explored whether patients with MdDS exhibit altered corticospinal and intracortical excitability. In a case-control study we compared patients with MdDS to age- and sex-matched controls (n=8/group). Postural stability (σr) was quantified from plane phase plots based on center or pressure, and psychological indices of depression, fatigue and kinesiophobia were obtained. Transcranial magnetic stimulation (TMS) was used to assess corticospinal excitability by quantifying the motor evoked potential (MEP) amplitude of the flexor carpi radialis, and intracortical excitability was assessed by quantifying indices of intracortical facilitation (ICF), and short-interval and long-interval intracortical inhibition using a paired-pulse TMS paradigm. The patients with MdDS exhibited greater mean (±standard error of the mean) σr during semi-tandem stance (10.9±1.5 compared to 7.1±0.7, p=0.04), higher levels of kinesiophobia (41.6±2.8 compared to 27.3±2.2), and higher levels of fatigue (27.0±4.1 compared to 48.4±1.0). Patients with MdDS exhibited a higher mean motor threshold (MT) (58.1±2.5 compared to 47.4±2.7% of stimulator output), and larger MEP (13.1±3.1 compared to 5.1±1.2% of maximal compound muscle action potential) but there was no difference in measures of intracortical excitability. These findings suggest that patients with MdDS exhibit impaired postural stability, and high levels of kinesiophobia and fatigue. Additionally, we observed that patients with MdDS exhibit higher MT and large MEP amplitudes, but do not exhibit differences in measures of intracortical excitability, compared to controls. These findings help characterize MdDS, and provide insight into the physiology of MdDS.

Validity of the Nintendo Wii® balance board for the assessment of standing balance in Parkinson’s disease

Background: Impaired postural stability places individuals with Parkinson’s at an increased risk for falls. Given the high incidence of fall-related injuries within this population, ongoing assessment of postural stability is important. Objective: To evaluate the validity of the Nintendo Wii® balance board as a measurement tool for the assessment of postural stability in individuals with Parkinson’s. Subjects: Twenty individuals with Parkinson’s participated. Intervention: Subjects completed testing on two balance tasks with eyes open and closed on a Wii® balance board and biomechanical force platform. Main Measures: Bland–Altman plots and a two-way, random-effects, single measure intraclass correlation coefficient model were used to assess concurrent validity of centre-of-pressure data. Results: Concurrent validity was demonstrated to be excellent across balance tasks (intraclass correlation coefficients = 0.96, 0.98, 0.92, 0.94). Conclusions: This study suggests that the Wii® balance board is a valid tool for the quantification of postural stability among individuals with Parkinson’s.

The interaction between the location of lower extremity muscle fatigue and visual condition on unipedal postural stability

The purpose of this study was to investigate the effects of unilateral muscle fatigue induced on the hip flexors/extensors or the ankle plantar/dorsiflexors on unipedal postural stability under different visual conditions. Twenty-four healthy young women completed 2 testing sessions 1 week apart with a randomized order assigned according to the muscles tested. During each session, one set of muscle groups was fatigued using isokinetic contractions: ankle plantar/dorsi flexors or hip flexor/extensors. Postural stability was assessed during trials of unilateral stance on a force plate before and after the fatigue protocol. 10 s into the trial, subjects were asked to close their eyes. Mean velocity, the area of the 95% confidence ellipse, and standard deviation of velocity in anteroposterior and mediolateral directions of center of pressure displacements were calculated for two periods of 5 s, immediately before and 1 s after the eyes closure. The results of the repeated measures ANOVAs showed a significant fatigue-by-fatigue segment by visual condition interaction for the CoP parameters. When the vision was removed, the interaction between fatigue and fatigue segment was significant for the CoP parameters. In conclusion, fatigue in both proximal and distal musculature of the lower extremity yielded decreased postural stability during unipedal quiet standing in healthy young women. This effect was more accentuated when visual information was eliminated. Withdrawing vision following fatigue to the proximal musculature, led to a significantly greater impairment of postural stability compared to the fatigue of more distal muscles.

Influence of risperidone on balance control in young healthy individuals

It has previously been shown that impairment of postural stability is a side effect of typical antipsychotic drugs, which are largely administered to control psychosis and behavioral symptoms in elderly patients. Surprisingly, no study has yet addressed this problem with second-generation antipsychotics. The objective of this study was to determine the extent to which risperidone at low doses altered balance control in healthy participants. Twelve healthy young adults received, following a randomized double-blind crossover design, a single oral dose of placebo, 1 and 3mg of risperidone on separate days at least 14days apart. Evaluation of extrapyramidal symptoms using the Extrapyramidal Symptom Rating Scale-abbreviated scoring form (ESRS-A) and measures of postural sway using a force platform were assessed over 9h following drug ingestion. There is a significant increase in the postural stability item of the ESRS-A parkinsonism subscale at 3 and 6h following 3mg of risperidone only when compared to placebo. With regard to balance control, body sway measures were increased at 1mg of risperidone but more pronounced at 3mg. The peak effects were observed at 3h after administration of the drug and had not completely returned to baseline after 9h. Risperidone administered at low doses did not elicit clinically detectable EPS but had significant effects on balance control. A dose-response effect on impairment of balance was observed that followed the expected time course of the drug pharmacokinetics. These results are likely to apply to older or demented individuals who have pre-existing balance control deficit.

Reliability of the TekScan MatScan® system for the measurement of postural stability in older people with rheumatoid arthritis

BackgroundPostural stability can be measured in clinical and research settings using portable plantar pressure systems. People with rheumatoid arthritis (RA) have decreased postural stability compared to non-RA populations and impaired postural stability is associated with falls in people with RA. The purpose of this study was therefore to investigate the reliability of the TekScan MatScan® system in assessing postural stability in people with RA.MethodsTwenty three participants with RA, mean (SD) age 69.74 (10.1) years, were assessed in barefoot double-limb quiet standing, with eyes open and eyes closed, for antero-posterior and medio-lateral postural sway values. Three repetitions, at a sampling frequency of 40 Hz, were recorded for each test condition to obtain a mean value. Measurements were repeated one hour later. Intraclass correlation coefficients (ICC) with 95% confidence intervals (CI) were calculated to determine between-session reliability. Measurement error was assessed through the calculation of the standard error of the measurement (SEM) and the smallest real difference (SRD).ResultsThe system displayed good to excellent reliability for antero-posterior and medio-lateral sway, with eyes open and closed, as indicated by ICC values ranging from 0.84 to 0.92. Measurement error, as evidenced by the SEM, ranged from 1.27 to 2.35 mm. The degree of change required to exceed the expected trial to trial variability was relatively high, compared to mean values, with SRD ranging from 3.08 to 5.71 mm.ConclusionsThe portability and ease of use of the TekScan MatScan® makes it a useful tool for the measurement of postural stability in clinical and research settings. The TekScan MatScan® system can reliably measure double-limb quiet standing in older people, aged 60 to 80 years, with RA.

Vibration-enhanced posture stabilization achieved by tactile supplementation: May blind individuals get extra benefits?

Diminished balance ability poses a serious health risk due to the increased likelihood of falling, and impaired postural stability is significantly associated with blindness and poor vision. Noise stimulation (by improving the detection of sub-threshold somatosensory information) and tactile supplementation (i.e. additional haptic information provided by an external contact surface) have been shown to improve the performance of the postural control system. Moreover, vibratory noise added to the source of tactile supplementation (e.g. applied to a surface that the fingertip touches) has been shown to enhance balance stability more effectively than tactile supplementation alone. In view of the above findings, in addition to the well established consensus that blind subjects show superior abilities in the use of tactile information, we hypothesized that blind subjects may take extra benefits from the vibratory noise added to the tactile supplementation and hence show greater improvements in postural stability than those observed for sighted subjects. If confirmed, this hypothesis may lay the foundation for the development of noise-based assistive devices (e.g. canes, walking sticks) for improving somatosensation and hence prevent falls in blind individuals.

Tests of dorsolateral frontal function correlate with objective tests of postural stability in early to moderate stage Parkinson’s disease

A substantial number of individuals with Parkinson’s disease who display impaired postural stability experience accelerated cognitive decline and an increased prevalence of dementia. To date, studies suggest that this relationship, believed to be due to involvement of nondopaminergic circuitry, occurs later in the disease process. Research has yet to adequately investigate this cognitive-posturomotor relationship especially when examining earlier disease states. To gain greater understanding of the relationship between postural stability and cognitive function/dysfunction we evaluated a more stringent, objective measure of postural stability (center of pressure displacement), and also more specific measures of cognition in twenty-two patients with early to moderate stage Parkinson’s disease. The magnitude of the center of pressure displacement in this cohort was negatively correlated with performance on tests known to activate dorsolateral frontal regions. Additionally, the postural stability item of the UPDRS exhibited poor correlation with the more objective measure of center of pressure displacement and all specific measures of cognition. These results may serve as rationale for a more thorough evaluation of postural stability and cognition especially in individuals with mild Parkinson’s disease. Greater understanding of the relationship between motor and cognitive processes in Parkinson’s disease will be critical for understanding the disease process and its potential therapeutic possibilities.

Impaired postural stability as a marker of premanifest Huntington's disease

Subtle changes in fine motor control have been observed in individuals who carry the Huntington's disease (HD) mutation but have not yet manifested symptoms, referred to as premanifest HD (preHD). However, few studies have examined gross motor impairments in this population. This study sought to examine the role of sensory involvement in maintaining postural stability during the premanifest and manifest stages of HD using computerized dynamic posturography. Eleven HD participants, 22 preHD subdivided into "preHD Near" (<5 years from estimated clinical onset) and "preHD Far" (>5 years from estimated clinical onset), and 17 nongene carriers (NGC) completed a sensory organization test (SOT) to assess postural control when vestibular, visual, and somatosensory information was systematically degraded. The HD group demonstrated greater postural sway than the NGC and preHD Far groups on all conditions including baseline, and greater postural sway than the preHD Near group when sensory information was manipulated. The preHD Near group showed significantly greater postural sway than the preHD Far group when visual and somatosensory information was degraded and only vestibular information was available and reliable for maintaining postural stability. The results of this study highlight subtle postural deficits in the face of changing sensory conditions in preHD up to 5 years before estimated disease onset. The findings suggest that the SOT may be a highly sensitive indicator of early motor impairment and subsequent phenoconversion to manifest HD in preHD.

Falls and their effects on people with rheumatoid arthritis

Falls in adults and older people are a major public health concern in terms of mortality, morbidity and costs to health and social services. Rheumatoid arthritis (RA) is linked to...

Assessment of postural control in patients with Parkinson’s disease: Sway ratio analysis

Analysis of the postural stability impairments in neurodegenerative diseases is a very demanding task. Age-related declines in posturographic indices are usually superimposed on effects associated with the pathology and its treatment. We present the results of a novel postural sway ratio (SR) analysis in patients with Parkinson’s disease (PD) and age-matched healthy subjects. The sway ratios have been assessed based upon center of foot-pressure (CP) signals recorded in 55 parkinsonians (Hoehn and Yahr: 1–3) and 55 age-matched healthy volunteers while standing quiet with eyes open (EO) and then with eyes closed (EC). Complementing classical sway measure abnormalities, the SR exhibited a high discriminative power for all controlled factors: pathology, vision, and direction of sway. Both the anteroposterior (AP) and mediolateral (ML) sway ratios were significantly increased in PD patients when compared to the control group. An additional SR increase was observed in the response to eyes closure. The sway ratio changes documented here can be attributed to a progressive decline of a postural stability control due to pathology. In fact, a significant correlation between the mediolateral SR under EO conditions and Motor Exam (section III) score of the UPDRS was found. The mediolateral sway ratios computed for EO and EC conditions significantly correlated with the CP path length ( r = .87) and the mean anteroposterior CP position within the base of support ( r = .38). Both indices reflect postural stability decline and fall tendency # in parkinsonians. The tremor-type PD patients ( N = 34) showed more pronounced relationships between the mediolateral SR and selected items from the UPDRS scale, including: falls (Kendall Tau = .47, p < .05), rigidity (.45, p < .05), postural stability (retropulsion) (.52), and the Motor Exam score (.73). The anteroposterior SR correlated only with tremor (Kendal Tau = .77, p < .05). It seems that in force plate posturography the SR can be recommended as a single reliable measure that allows for a better quantitative assessment of postural stability impairments.

Postural instability at a simulated altitude of 5,000 m before and after an expedition to Mt. Cho-Oyu (8,201 m)

To clarify the effects of altitude acclimatization on postural instability at altitudes, six female climbers stood with their eyes open or closed on a force-measuring platform under normoxia (NC) and hypobaric hypoxia, equivalent to a 5,000 m altitude (HC), before and after an expedition to Mt. Cho-Oyu (8,201 m). The expedition extended over 84 days. We recorded sways in the center of foot pressure, electromyograms (EMGs) of lower-leg muscles, blood components and arterial oxygen saturation (SpO(2)). Before the expedition, the maximum amplitude of sway with the eyes open and integrated EMG from the medial gastrocnemius increased for HC. After the expedition, red blood cell (from 423.4 ± 15.4 to 498.0 ± 24.5 × 10(4) μl(-1)), hemoglobin content (from 12.6 ± 0.32 to 14.5 ± 1.00 g/dl) and 2,3-diphosphoglycerate (from 1.93 ± 0.21 to 2.24 ± 0.34 μmol/ml) increased. The SpO(2) under HC increased from 69.2 ± 9.6 to 77.2 ± 10.0%. The maximum amplitude of sway with the eyes open decreased for HC. No difference in the sway path length and integrated EMGs was observed between NC and HC. These results suggest that acclimatization can improve the impaired postural stability on initial arrival at altitudes. However, it is still unclear how long acclimatization period is needed. Further studies are needed to reveal this point.

S-11 Acromioclavicular Joint Pain in Whiplash Injuries to Shoulder

The kinetic chain theory is widely used as a rationale for the inclusion of core stability training in athletes. Core stability (muscle capacity and neuromuscular control) impairments may result in less than optimal performance and abnormal force dissipation to the shoulder complex that could lead to shoulder injuries. However, a paucity of literature exists to support this relationship, and no previous studies have investigated the relationship between isolated core neuromuscular control and shoulder injuries. Additionally, lower extremity postural stability has been associated with athletic function and may also be associated with shoulder injuries. The purpose of this study was to compare biomechanical measures of isolated core neuromuscular control and lower extremity postural stability between athletes with and without non-traumatic shoulder injuries.Eighty athletes (55 males, age: 21.2 ± 3.3 years, 40 with a current shoulder injury) completed biomechanical measures of isolated core neuromuscular control and lower extremity postural stability. Athletes were matched by age, gender, body mass index, and sport type. MANOVAs were used to assess differences between measures of core neuromuscular control and lower extremity postural stability between groups.There were no statistically significant differences between athletes with and without shoulder injuries for the static core neuromuscular control measures, F(4,75) = 0.45, P = 0.78, η2 = 0.02; dynamic core neuromuscular control measures, F(4,75) = 0.81, P = 0.52, η2 = 0.04; or lower extremity postural stability measures, F(8,61) = 0.85, P = 0.56, η2 = 0.10.Although core stability is widely incorporated in rehabilitation of athletes with shoulder injuries, athletes with current non-traumatic shoulder injuries may not present with impairments in core neuromuscular control or lower extremity postural stability.

Deficits in Postural Stability Following Concussion Persist Beyond BESS Recovery

Assessment of postural stability is a cornerstone of concussion management and the most common assessment tool is the Balance Error Scoring System (BESS). However, BESS has been criticized for the static nature of the assessment. Gait initiation (GI) is a dynamic task which has been effectively identified impairments in postural stability within diverse populations. PURPOSE: The purpose of this study was to investigation impairments in dynamic postural stability following concussion. METHODS: 15 subjects (19.7 + 1.5 years old; 183.7 + 13.1cm; 84.8 + 29.6kg) performed three trials of GI daily from the day after their concussion (Cantu Revised Scale: Grade I - 1, Grade II - 12, Grade III - 2) till their return to play day (mean 10.2 + 3.7 days). Kinetic data was collected by two forceplates (AMTI, Watertown, MA) at 1000hz. All subjects underwent pre-season testing of the BESS. Dependent variables included the posterior and lateral displacement of the center of pressure (COP) during the anticipatory postural phase (S1) of GI as well as step length and velocity. Within subjects comparisons were made between first day after the concussion (Day1), the day the BESS score returned to baseline (BESS), and the return to play (RTP) day using a one-way repeated measures ANOVA. RESULTS: Mean time for BESS to return to baseline was 3 days (range: 1 - 9 days) post concussion. Significant differences were present between BESS day and RTP day for posterior movement of the COP during S1 (3.08 + 2.3cm and 6.3 + 2.0cm, p=0.001), step length (63.0 + 11.9cm and 72.9 + 10.7cm, p=0.025), and a trend for step velocity (0.63 + 0.21m/s and 0.78 + 0.17m/s, p=0.116). There were no differences between Day 1 and BESS day for posterior or lateral movement of COP during S1 (p=0.139 and 0.916 respectively), step length (p=0.481), or step velocity (p=0.989). CONCLUSION: The results of this study support recent findings suggesting that impairments in postural stability persist despite the BESS returning to baseline values. Additionally, the lack of improvement during the dynamic task between day 1 and the time the BESS returned to baseline value raises further concern of the sensitivity of the BESS to identify impairments in postural stability. In light of this and other recent findings, clinicians should exercise caution in interpreting BESS results.

Postural instability in Charcot-Marie-Tooth type 1A patients is strongly associated with reduced somatosensation

In order to determine the influence of somatosensory impairments, due to the loss of large myelinated fibres, on the postural stability of Charcot-Marie-Tooth 1A (CMT) patients, a cross-sectional balance assessment was done. Nine CMT patients were compared with eight patients with a distal type of Spinal Muscular Atrophy (SMA), and 11 healthy control subjects. The balance assessment consisted of four tasks: quiet barefoot standing on a stable versus compliant surface, with eyes opened or closed. Force plate signals were used to calculate the velocity of the centre of pressure of the ground reaction forces. The patients’ distal muscle force (MRC scale), vibration detection threshold (Rydel-Seiffer tuning fork) and superficial tactile sensation (Semmes-Weinstein monofilaments) were clinically assessed. Compared to the healthy subjects, postural stability of both patient groups was seriously impaired, however, increased visual dependency was only found in the CMT patients. The postural instability of the CMT patients correlated significantly with decreased vibration sense only. The strength of the correlation increased with task complexity. It is concluded that somatosensory deficits substantially contribute to impaired postural stability and increased visual dependency in CMT patients.

Vestibulospinal responses in motor incomplete spinal cord injury

Objective Postural instability limits ambulatory capacity in patients with spinal cord injury (SCI). Galvanic vestibular stimulation (GVS) was used to investigate the integrity of vestibulospinal pathways and related changes in postural responses in SCI. Methods Binaural bipolar galvanic stimuli of 400 ms duration and 3 mA intensity were applied in 8 motor incomplete SCI and 8 control subjects who stood facing towards the left. EMG responses were recorded from the right soleus muscle and the trajectory of the centre of pressure (CoP) was measured with a force plate. Results There was no difference in excitability and amplitude of the responses between the groups. However, the latency and duration of the medium latency EMG response and all CoP responses were significantly longer in the SCI group. Additionally, postural stability was reduced in the SCI group, as shown by a greater tendency to fall due to GVS. Conclusions Despite early EMG responses proving the basic connectivity of the direct vestibulospinal pathways, the delayed GVS responses suggest a vestibulospinal deficit in the SCI subjects. Significance GVS can be applied in incomplete SCI to supplement the neurological examination by revealing changes in vestibulospinal responses and impairment of postural stability.

Impaired Postural Stability in Patients With Cervical Myelopathy

A prospective clinical study. To quantitatively evaluate impairment of postural stability in patients with cervical myelopathy. Proprioceptive sensation plays an important role in coordinated movement of the lower extremities and postural stability. Nevertheless, although disturbance of proprioceptive information will have an influence on the maintenance of postural stability, there have been few studies dealing with deterioration of postural stability in patients with cervical myelopathy. We investigated 52 cervical myelopathy patients who could stand without support and compared the results with those of 29 age-matched healthy volunteers. Postural stability was examined using a stabilometer. In the stabilometer, sway of gravity center was measured at upright position with eyes closed for 30 seconds. We used 2 parameters for evaluation: environmental area (EA), which measures degree of sway of the gravity center, and locus length per environmental area (L/EA), which measures fine control of standing posture by proprioceptive reflexes. The mean EA of the patient group was 13.9, whereas that of the control group was 2.74, revealing significantly larger postural instability in the patient group compared to the control group. The L/EA of the patient group was significantly worse than the control group. It was also shown that postural instability was significantly larger in the myelopathy patients with the severe clinical symptoms. The results of the present study demonstrate impairment of postural stability in patients with cervical myelopathy. The stabilometer can objectively evaluate the postural stability, which may reflect the function of the dorsal columns and the corticospinal tracts. Thus, stabilometry is a useful method for measuring a part of proprioceptive function and for objective assessment of the lower limb function of cervical myelopathy.

Sensory-Specific Balance Training in Older Adults: Effect on Proprioceptive Reintegration and Cognitive Demands

Age-related changes in the ability to adjust to alterations in sensory information contribute to impaired postural stability. The purpose of this randomized controlled trial was to investigate the effect of sensory-specific balance training on proprioceptive reintegration. The subjects of this study were 36 older participants who were healthy. Participants were randomly assigned to a balance exercise group (n=17) or a falls prevention education group (n=19). The primary outcome measure was the center-of-pressure (COP) velocity change score. This score represented the difference between COP velocity over 45 seconds of quiet standing and each of six 5-second intervals following proprioceptive perturbation through vibration with or without a secondary cognitive task. Clinical outcome measures included the Fullerton Advanced Balance (FAB) Scale and the Activities-specific Balance Confidence (ABC) Scale. Assessments were conducted at baseline, postintervention, and at an 8-week follow-up. Following the exercise intervention, there was less destabilization within the first 5 seconds following vibration with or without a secondary task than there was at baseline or in the falls prevention education group. These training effects were not maintained at the 8-week follow-up. Postintervention improvements also were seen on the FAB Scale and were maintained at follow-up. No changes in ABC Scale scores were identified in the balance exercise group, but ABC Scale scores indicated reduced balance confidence in the falls prevention education group postintervention. The results of this study support short-term enhanced postural responses to proprioceptive reintegration following a sensory-specific balance exercise program.

Effect of Styrene on Postural Stability Among Reinforced Plastic Boat Plant Workers in Finland

Many drugs are vestibulotoxic and may impair balance. Styrene is both ototoxic and neurotoxic, but its effect on balance has been little studied. We evaluate the effect of low concentrations of styrene on balance among Finnish fiberglass-reinforced plastic boat manufacturers. From 252 male employees, we measured postural stability and urine mandelic and phenylglycolic acid concentrations. Individual exposure to styrene in breathing zone was measured for 148 workers. For analysis, 88 matched pairs were selected. The postural stability of laminators was aggravated compared with nonlaminators. This impairment was observed in young workers, and it worsened with age. This study documents styrene as an additional risk factor in impaired postural stability, with the negative effects of the styrene exposure starting already in younger workers.

Association of Pontine Small Infarction (Lacuna) with Disturbance of Postural Stability

Neuronal degeneration within the brainstem has been reported in patients with impaired postural stability. However, the functional significance of these abnormalities is unknown at present. In the present study, we evaluated the relationship between the presence of pontine lacunae and postural stability measured by stabilometry. A total of 209 consecutive patients without neurological signs were divided into three groups according to the territory of lacunae on magnetic resonance imaging: (1) non-lacunar group, (2) pontine lacunar group, and (3) non-pontine lacunar group. Stabilometry was performed and statokinesigram measures including each Romberg quotient were compared among the three groups. Using multivariate analysis, postural stability was found to be disturbed in the pontine lacunar group compared with the other groups. The data of stabilometry in this group were compatible with disturbance of the central controlling system for keeping postural stability. Pontine lacuna is associated with patients with postural instability. This result may be related to the deterioration of the central coordination system for posture and locomotion.

The effect of aging on postural stability: a cross sectional and longitudinal study

Aims of the study. – Only a good knowledge of the effects of age on postural stability allows differentiating between physiological aging and pathologies leading to its impairment. The aims of this study were to define the posturographic parameters which best reflected the effects of aging on postural stability and to determine the slope of postural stability impairment related to aging. Patients and methods. – Postural stability of 50 normal volunteers aged 25–83 years (55.4) was studied with one Kistler force plate. Subjects were asked to stand for 30 s on two-legged stance, eyes open then closed. The center of pressure displacement (COPd) and velocities (COPv), in the antero-posterior ( x) and the medio-lateral ( z) axis, the sway axis, and the integral of COP displacement vs. time were computed. Eleven subjects were retested at 3 and 6 months to estimate the reliability of posturographic measurements. In addition, 28 subjects aged 25–83 years (60.2) were retested 2.2 years after their first posturographic assessment. Results. – COPxv best reflected postural stability impairment with aging. Closure of the eyes increased the variance of the results. This change was higher in subjects more than 60 years old: 0.019–0.157 cm 2 s –2 than in younger ones: 0.011–0.043 cm 2 s –2. Retesting at 3 and 6 months showed a reliability of 79%. According to the cross-sectional part of the study, the slope of postural stability impairment with aging was estimated at 0.0038 cm/s/year. These results were confirmed by the longitudinal part of the study, which showed that COPxv increased from 0.66–0.75 cm/s/year ( P = 0.0001) (slope = 0.0041 cm/s/year). Conclusion. – (1) Measurement of COPxv, on two-legged stance, is a simple and reliable way to assess postural stability. (2) Thanks to both a cross sectional and a longitudinal study, the rate of postural stability impairment due to aging was precisely estimated, which will be useful to help distinguishing between the part of postural stability impairment attributable to aging from the one due to neuro-degenerative diseases.