The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 58:M525-M530 (2003)
© 2003 The Gerontological Society of America
Changes in Postural Stability in Women Aged 20 to 80 Years
Nancy Low Choy,
Sandra Brauer and
Jennifer Nitz
Department of Physiotherapy, The University of Queensland, St. Lucia, Australia.
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Abstract
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Background. A study of postural stability was undertaken to identify the relationship between vision and support surface across age decades. Understanding when reliance on vision for postural stability emerges and the support conditions contributing to this instability may provide the evidence required to introduce falls-prevention strategies in younger age decades.
Methods. We measured postural stability in 453 women aged 20 to 80 years using the Balance Master force-plate system while the women performed the modified Clinical Test for the Sensory Interaction and Balance (firm and foam surfaces, eyes open and closed) and the Single-Limb Stance Test (eyes open and closed).
Results. Women in their 60s and 70s were more unstable than younger women in bilateral stance on a firm surface with the eyes closed. This instability was evident from the 50s when a foam surface was introduced and from the 40s when single-limb stance was tested with eyes closed. A further decline in stability was demonstrated for each subsequent decade when the eyes were closed in single-limb stance.
Conclusions. Age, visual condition, and support surface were significant variables influencing postural stability in women. Reliance on vision for postural stability was evident for women from the 40s when single-limb stance was tested, from the 50s when bilateral stance on foam was tested, and from the 60s when a firm surface was used. The cause(s) of this decline in stability requires further investigation, and screening for postural instability between the ages of 40 and 60 is advocated.
FALLS in the elderly are a growing international problem with significant economic, personal, and social costs as 1 in 3 people older than 65 years fall in a 12-month period (1–4). Poor balance has been identified as one of the major risk factors for falls, and one of the few able to be improved with intervention as there is considerable knowledge related to the major systems associated with the control of balance (5,6). Along with raising awareness of slips, trips, and falls (7,8) and the contribution of environmental factors to falls (9), intervention programs have targeted persons aged 65 years and older, focusing on balance improvement to reduce the incidence of falls and related injuries (10–14). Despite these considerable efforts, a recent audit of the trends in community, hospital, and mortality data in older Australians demonstrated that falls-prevention activity during the 1990s has not reduced the magnitude of this major public health problem (15). For this reason, it is important to investigate factors that may be indicators of early changes in postural control so that additional strategies may be considered for implementation in earlier age decades.
It is known that function of the sensory system degrades after the age of 65 years, to the extent that it can adversely impact balance and contribute to falls. A reduction in somatosensation (2,5,16–20) and vestibular function (2,5,18,20–25) has been strongly linked to postural instability in elderly adults. This reduction in proprioception and vestibular function could lead to an increased reliance on vision to maintain balance. The age at which visual reliance first emerges however is not clear, although an earlier study (26) suggested a decline in stability as early as the 40s when the eyes were closed in bilateral stance. Further investigation is warranted to identify the support conditions when reliance on vision first emerges so that falls-prevention strategies target appropriate younger age groups in the community.
As falls are considered more prevalent in elderly women (1–3,27), and because there are differing reports related to gender differences on postural stability and balance with age (27–31), a study that focused on the balance ability of women across the adult life span was prioritized. Thus, we undertook a study of age-related changes in postural stability in women under several sensory conditions as a cross-sectional study of balance in women aged 20 and 80 years.
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Methods
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We used a cross-sectional design to assess postural stability and balance ability in women sampled from age-decade cohorts from 20 to 80 years.
Subjects
The subjects were registered at a research center for women and aging that was established to carry out a longitudinal study of women aged 40 to 80 years. The electoral roll had been used to contact 2000 women from a major metropolitan city and nearby rural area (within 100 km). A total of 500 women were recruited (125 women for each age decade) who were community dwelling and ambulatory without an aid, able to give informed consent, and able to undertake a comprehensive assessment. Each woman had consented to be part of a multidimensional project and completed a medical review, a cognition evaluation, and a nutritional consultation. No women with dementia were recruited. For this study of balance, women were excluded if they had a diagnosed pathology that could account for changes in postural stability (6). Thus, women were excluded if they had neurologic disorders; dizziness, uncorrected vision, insulin-dependent diabetes, peripheral neuropathy, or peripheral vascular disease that required active management or surgical intervention; or major musculoskeletal dysfunction. In addition, women taking medication for psychiatric disorders, depression, or anxiety were excluded from this study as an association of such medications with falls has been demonstrated (32). As a result of this process, 366 of the women registered at the research center were admitted to this study. To recruit subjects aged 20 to 40 years, we placed an advertisement in the newspaper servicing the same metropolitan and rural regions. This yielded an additional 87 volunteers, to provide a total of 453 women for this study. The cohort was considered to be a representative group of healthy young and aging adults living independently in the community.
All subjects attended 1 test session, which began with a short interview to confirm that the subjects met the inclusion and exclusion criteria. A self-report record was made of the number of unexplained falls experienced in the previous 2 years (7), current medications, comorbidities, and activity level, as these factors may influence postural stability (14). Height and age were recorded and entered into the Neurocom Data Base System in preparation for testing balance.
Measures
Tests of balance were selected that included a protocol in which vision could be removed and the support surface could be altered. For this reason, we selected the modified Clinical Test for the Sensory Integration of Balance (CTSIB) (33), and the Single-Limb Stance Test (SLST) (27,34). The modified CTSIB has established validity (22–24,35,36) and retest and intertester reliability (37). The test allows manipulation of the senses and determination of reliance on vision under conditions of proprioceptive conflict. When the proprioceptive system is challenged by standing on a high-density foam pad (22) with the eyes closed, the vestibular system assists to resolve this conflict and maintain postural stability. When the vestibular system is inefficient, elderly adults may experience increased postural sway and/or a fall (2,5,18,20–25). The SLST further challenges balance with the narrower base of support, and the removal of vision reveals those subjects reliant on vision for balance. As the SLST has been shown to be an important predictor of injurious falls in older persons (38), we included this test. The velocity of sway was measured during the performance of these tests, as the validity of using force-plate measures to record stance stability under varying sensory conditions has been established (27–31,37,39,40).
All subjects performed 3 repetitions of 8 balance tasks while standing on the Neurocom Force-Plate System (Balance Master 6.0, NeuroCom, OR). These tasks included bilateral stance on a firm surface with eyes open and eyes closed; bilateral stance on a 15-cm closed-cell, high-density (3.75 lb/cu. ft) foam block (22) with eyes open and eyes closed; and SLST on the left and right leg with eyes open and eyes closed. The Balance Master System has 3 positions for the feet according to the height of the subject. The outer border of the heel was set 19 cm apart for subjects 76 to 140 cm in height; 26 cm apart for subjects between 141 and 165 cm in height; and 30.5 cm apart for subjects 166 to 203 cm in height. The toe-out angle was controlled by allowing an additional 2 cm between the first metatarsal heads as compared with the distance between the heels. Each balance task was held for three 10-second trials (the standard time for measuring sway on this system) or less if the subject could not hold the position unsupported, or until foot-down for the SLST. The 10-second recording also allowed comparison across age decades, as many 60- and 70-year-olds have difficulty completing the test conditions when 30 consecutive seconds are used in trials (22,23,27,28).
Data Analyses
Descriptive statistics were analyzed for each measure recorded. A repeated-measures ANOVA was carried out to determine the effect of vision (eyes open and eyes closed) and support surface (firm vs foam; bilateral vs single-limb stance) on postural stability across 6 age decades. Post hoc analyses using Bonferroni multiple comparisons were applied to identify between which age decades the significant changes occurred for the dependent variables. Pearson r correlations were used to test the strength of the correlation between age and the balance tasks.
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Results
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The descriptive statistics for the postural stability tests across the age decades for the women enrolled in the study are presented in Table 1 and illustrated in Figure 1. A highly significant 2-way interaction was found for age and visual condition, age and support conditions, and vision and support conditions (Table 2). This table also summarizes the highly significant 3-way interaction yielded between vision condition, support surfaces, and age. Thus, an analysis for a main effect of vision or support surface was not included. This interaction is clearly illustrated by the data in Figure 2, wherein varying rates of decline in stability are illustrated according to age decade, the support conditions, and whether vision was available or removed by closing the eyes. An exponential curve is evident when the eyes are open and a challenging support surface is introduced (foam and single-limb conditions as depicted in Figures 2A and 2C). In contrast, with the eyes closed under these challenging surface conditions (Figures 2B and 2D), an earlier decline in stability is apparent from the 40s, although the rate of this decline is reduced from the 60s under these conditions.
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Figure 1. Mean (SD) sway velocity (meters per second) for visual and support conditions across age decades
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Figure 2. Effects of age, vision, and support surface on the estimated marginal means: sway velocity (meters per second)
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Post hoc analyses of these data confirmed a significant decline in postural stability with age under the varying visual conditions (Table 3). The modified CTSIB test revealed that a significant decline in stability (increased sway velocity) occurred by the 60s when vision was removed while standing on a firm surface, although there was no further significant decline in stability in the 70s. For the foam conditions, this decline in stability was apparent from the 50s when compared with the ability of women in their 20s and 30s but not when compared with the balance of women in their 40s. There was also a significant further decline in stability for women in their 60s and 70s when the eyes were closed during this test. For the SLST on either limb (eyes open vs eyes closed), a decline in postural stability was evident by the 40s, and an ongoing decline for each subsequent decade was found. For all tests of postural stability, there was no significant difference in balancing ability between women in their 20s and those in their 30s.
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Table 3. Effect of Visual Condition on Postural Stability Across the Age Decades: Mean Difference (Age Decade A – B) in Sway Velocity.
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There was a strong association between age decade and balance for each of the support conditions (Table 4). The post hoc analyses demonstrated that while vision could be used, a significant decline in the ability to balance occurred from the 60s when a surface change (firm to a foam surface) was introduced in bilateral stance. This instability was significant from the 50s when vision was removed compared with women in their 20s and 30s, although there was no significant difference between women in their 40s compared with women in their 50s. When postural stability was challenged by changing from bilateral stance to SLST on either leg, it was clear that postural stability was maintained until the 60s while vision could be used, and a further decline in stability occurred in the 70s. Once vision was removed, however, there was a significant decline in postural stability by the 40s and for each subsequent decade until the 70s.
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Table 4. The Effect of Support Surface on Postural Stability Across the Age Decades: Mean Difference (Age Decade A – B) in Sway Velocity (Meters Per Second).
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The Pearson r correlations demonstrated a moderate correlation between age and the performance on SLST (eyes open and closed) and bilateral stance on the foam surface with the eyes closed (
). A significant but weaker correlation was found for age and bilateral stance on a firm surface (eyes open and eyes closed) and on a foam surface with eyes open (
).
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Discussion
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The decline in postural stability that occurs with age in women was confirmed in this study, and the findings concur with earlier research that demonstrated increased sway with age (26–31,41). In addition, this study provides evidence related to the age decade when reliance on vision for postural stability emerges for each of the visual and support conditions investigated. Single-limb stance with the eyes closed showed the earliest differences in postural stability between age decades, with a decline in mediolateral stability demonstrated for women from their 40s, and with a significant further decline with each subsequent decade.
This finding is important as inability to stand on one leg has been shown to be an important predictor of serious falls in older persons (38). The SLST has been advocated as a clinical measure for higher-level balance ability (27,34,42–44), and preliminary data for age-related norms have been developed (27), although some debate continues on the value of ordinal rather than timed balance tests (43). The findings of the current study suggest that the SLST could be incorporated as part of a screening protocol to identify women at increased risk in their 40s and 50s who could experience falls without effective active management. In developing a screening protocol for this test, further work needs to be undertaken to determine if the time to hold unilateral stance across the age decades to build on preliminary data from earlier studies (27,42,43). This aspect is currently being investigated by our research team.
This study also confirms that reliance on vision in women is definitive by the 60s, with a reduced ability to balance on both feet without vision even when the surface is firm. In our study, no further decline in stability occurred in the 70s as long as the surface was firm. This finding concurs with earlier studies wherein the increased instability with more advanced age was attributed to somatosensory changes (2,5,17). Earlier decline in the ability to balance without vision, however, occurred from the 50s when a soft surface (foam) was introduced. On the softer surface, the women were less able to balance with eyes closed than women in their 30s (although not significantly reduced to the balance ability of women in their 40s). The decreased ability to balance on a soft surface when vision is removed supports the view that detrimental changes may have occurred in the other sensory systems involved in postural stability (vestibular and/or somatosensory systems) by the 50s. As the performance on this test has been linked to a history of falls (1–4,13,22–25), there is a need to implement preventive strategies that target women before such changes in postural control are evident. The inclusion of the CTSIB as part of a screening protocol for potential fallers has been advocated by earlier research (2,5,16,28), and our findings strongly support this view. The timing of such screening is important to consider. Our research suggests that the target groups should be women in their 40s and 50s. Women who are overtly unstable on this test at this age could then be referred for active intervention before detrimental changes are established, thereby minimizing their risk of progression to a fall.
Our research results support previous reports of a decline in mediolateral stability in elderly adults. A delay in gluteus medius activation during a stepping task has been demonstrated with increasing age and identifies prospective fallers (45). In addition, decreased control of lateral stepping reactions in response to lateral perturbations has been found in elderly adults (46). Our research team has also found a decreasing ability to perform the step test, reach sideways, and explore the limits of stability when a decline in mediolateral stability presents with age (47). The performance on the step test was shown to be significantly reduced by the 50s, while a decreased ability to reach and to perform limits of stability tasks was evident by the 60s. The reason for this initial and subsequent decline in performance on postural stability and functional tasks over these decades requires further investigation, given that the moderate correlation between balance performance and age in our study highlights that factors other than those measured could be implicated.
An investigation of the changes in sensory, motor, and cognitive systems that occur when reliance on vision for postural control emerges could provide the evidence for the type and extent of prevention programs that need to be implemented. If falls-prevention strategies are to improve, this research becomes a priority as current intervention programs have focused on reducing the incidence of falls and related injuries in men and women older than 65 years (7,8,10–14). Although this focus is based on the prevalence of falls in adults in this age group (1–5), it is likely that the incidence of falls may not be reduced unless additional strategies are implemented. This view is given support by the recent meta-analysis of outcomes from falls-prevention programs in Australia (15), which demonstrated that the incidence of falls has not been reduced despite the attention to this area during the last decade. This may mean a greater emphasis on targeting age groups before the development of the detrimental changes that contribute to falls is required. It is clear that changes in postural stability are well established by age 60 when vision is not available and that the introduction of a soft surface or a reduced support base further challenges balance at an earlier age. These data emphasize the need to screen women earlier than their 60s and to introduce effective prevention strategies to minimize the decline in postural stability that may occur with advancing age.
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Acknowledgments
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We acknowledge the leadership and support provided by Professor Khoo, Team Leader of the Longitudinal Study of Ageing in Women 40 to 80 years (LAW Study); Dr. Sheila O'Neill, Director, Betty Byrne Henderson Centre for Women and Ageing, Royal Women's Hospital, Brisbane; the staff of the Betty Byrne Henderson Centre for Women and Ageing who assisted with recruitment and appointments of subjects for this study; and the Australasian Menopause Society for the equipment funding to purchase the Balance Master 6, NeuroCom System used in this study.
Address correspondence to Nancy Low Choy, Department of Physiotherapy the University of Queensland, St. Lucia, Qld-4072, Australia. E-mail: n.lowchoy{at}shrs.uq.edu.au
Received July 11, 2002
Accepted October 7, 2002
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References
|
|---|
- Cho C, Kamen G. Detecting balance deficits in frequent fallers using clinical quantitative evaluation tools. J Am Geriatr Soc.. 1998;46:426-430.[Medline]
- Lord SR, Clark RD, Webster IW. Physiological factors associated with falls in an elderly population. J Am Geriatr Soc.. 1991;39:1194-1200.[Medline]
- Lord SR, Ward JA, Williams P, Anstey K. An epidemiological study of falls in older community-dwelling women: the Randwich falls and fractures study. Aust J Public Health.. 1993;17:240-245.[Medline]
- Tinnetti ME, Speechley M, Ginter SF. Risk factors for falls among elderly persons living in the community. N Engl J Med.. 1988;319:1701-1707.[Abstract]
- Lord S, Ward J. Age-associated differences in sensori-motor function and balance in community dwelling women. Age Ageing.. 1994;23:452-468.[Abstract/Free Full Text]
- Woollacott MA. Systems contributing to balance disorders in older adults. J Gerontol A Biol Sci Med Sci.. 2000;55A:M424-M428.[Free Full Text]
- Peel N, Cartwright C, Steinberg M. Monitoring slips, trips and falls in the older community: preliminary results. Health Promot J Aust.. 1998;8:148-150.
- Steinberg M, Cartwright C, Peel N, Williams G. A sustainable program to prevent falls and near falls in community dwelling older people: results of a randomised trial. J Epidemiol Commun Health.. 2000;54:227-232.[Abstract/Free Full Text]
- Hinman MR. Causal attributions of falls in older adults. Phys Occup Ther Geriatr.. 1998;15:71-84.
- Lord S, Castell S. Physical activity program for older persons: effect on balance, strength, neuromuscular control and balance reaction time. Arch Phys Med Rehabil.. 1994;75:648-652.[Medline]
- Lord SR, Ward JA, Williams P, Strudwick M. The effect of a 12 month exercise trial on balance, strength and falls in older women. J Am Geriatr Soc.. 1995;43:1198-1206.[Medline]
- Lord SR, Ward JA, Williams P. Exercise effect on dynamic stability in older women: a randomised controlled trial. Arch Phys Med Rehabil.. 1996;77:232-236.[Medline]
- Shumway-Cook A, Gruber W, Baldwin M, Liao S. The effect of multidimensional exercises on balance, mobility and falls risk in community-dwelling older adults. Phys Ther.. 1997;77:46-57.[Abstract/Free Full Text]
- Tinetti M, Baker D. McAcay. A multi-factorial intervention to reduce the risk of falling among elderly people living in the community. N Engl J Med.. 1994;331:821-827.[Abstract/Free Full Text]
- Hill K, Kerse N, Lentini F, et al. Falls: a comparison of trends in community, hospital and mortality data in older Australians. Aging.. 2002;14:18-27.
- Anacker SL, Di Fabio RP. Influence of sensory inputs on standing balance in community-dwelling elders with a recent history of falling. Phys Ther.. 1992;72:575-584.[Abstract/Free Full Text]
- Heyley M, Rees J, Newham D. Quadriceps function, proprioceptive acuity and functional performance in healthy young, middle-aged and elderly subjects. Age Ageing.. 1998;27:55-67.[Abstract/Free Full Text]
- Manchester D, Woollacott M, Zederbauer-Hylton N, Marin O. Visual, vestibular and somatosensory contributions to balance control in the older adult. J Gerontol Med Sci.. 1989;44:M118-M127.
- Tanaka T, Hashimoto N, Noriyasu S, Ino S, Ifukube T, Mizumoto Z. Ageing and postural stability: changes in sensori-motor function. Phys Occup Ther Geriatr.. 1995;13:1-16.
- Peterka R, Black F. Age related changes in human posture control: sensory organisation tests. J Vestib Res.. 1990;1:73-85.[Medline]
- Whitney SL, Hudak MT, Marchetti GF. The association between observed gait instability and fall history in persons with vestibular dysfunction. J Vestib Res.. 2000;10:99-105.[Medline]
- Alhanti B, Bruder LA, Creese W, Golden RL, Gregory C, Newton R. Balance abilities of community dwelling older adults under altered visual and support surface conditions. Phys Occup Ther Geriatr.. 1997;15:37-52.
- Newton RA. Standing balance abilities of elderly subjects under altered visual and support conditions. Physiother Can.. 1995;47:25-29.
- Teasdale N, Stelmach G, Breunig A. Postural sway characteristics of the elderly under normal and altered visual and support surface conditions. J Gerontol A Biol Sci Med Sci.. 1991;46:B238-B244.
- Maki BE, Holliday PJ, Topper AK. A prospective study of postural balance and risk of falling in an ambulatory and independent elderly population. J Gerontol A Biol Sci Med Sci.. 1994;49:M72-M84.
- Sheldon JH. The effects of age on the control of sway. Geronol Clin.. 1963;5:129-138.
- Bohannon R, Larkin P, Cook A, Gear J, Singer J. Decrease in balance scores with ageing. Phys Ther.. 1984;64:1067-1070.
- Colledge N, Cantley P, Peaston I, Brash H, Lewis S, Wilson J. Ageing and balance: the measurement of spontaneous sway by posturography. Gerontology.. 1994;40:273-278.[Medline]
- Hageman PA, Leibowitz JM, Blanke D. Age and gender effects on postural control measures. Arch Phys Med Rehabil.. 1995;76:961-965.[Medline]
- Overstall PW, Exton-Smith AN, Imms FJ, Johnson AL. Falls in the elderly related to postural imbalance. BMJ.. 1977;1:261-264.
- Wolfson L, Whipple R, Derby C, Amerman P, Nasher L. Gender differences in balance of healthy elderly as demonstrated by dynamic posturography. J Gerontol Med Sci.. 1994;49:M160-M167.
- Leipzig M, Cumming R, Tinnetti M. Drugs and falls in older people: a systematic review and meta-analysis. I. Psychotropic drugs. J Am Gerontol Soc.. 1999;47:30-40.[Medline]
- Shumway-Cook A, Horak F. Assessing the influence of sensory interaction on balance. Phys Ther.. 1986;66:1548-1550.
- Newton R. Review of tests of standing balance abilities. Brain Inj.. 1989;3:335-338.[Medline]
- DiFabio RP, Badke MB. Relationship of sensory organization to balance function in patients with hemiplegia. Phys Ther.. 1990;70:542-548.[Abstract/Free Full Text]
- Cohen H, Blatchley CA, Gombash LL. A study of the Clinical Test of the Sensory Interaction and Balance. Phys Ther.. 1993;73:346-354.[Abstract/Free Full Text]
- Liston RA, Brouwer BJ. Reliability and validity of measures obtained from stroke patients using Balance Master. Arch Phys Med Rehabil.. 1996;77:425-430.[Medline]
- Vellas BJ, Wayne SJ, Romero L. One-legged balance is an important predictor of injurious falls in older persons. J Am Geriatr Soc.. 1997;45:735-738.[Medline]
- Di Fabio R. Meta-analysis of the sensitivity and specificity of platform posturography. Arch Otolaryngol Head Neck Surg.. 1996;122:150-156.[Medline]
- Hu M, Hung Y, Huang Y, Peng C, Shaw S. Validity of force plate measures for stance stability under varying sensory conditions. Life Sci.. 1996;20:78-86.
- Brocklehurst JC, Robertson D, James-Gordon P. Clinical correlates of sway in old age-sensory modalities. Age Ageing.. 1982;11:1-10.[Abstract/Free Full Text]
- Balogun J, Akindele K, Nihinlola J, Marzouk D. Age-related changes in balance performance. Disabil Rehabil.. 1994;16:58-62.[Medline]
- Bohannon RW, Walsh S, Joseph MC. Ordinal and timed balance measurements: reliability and validity in patients with stroke. Clin Rehabil.. 1993;7:9-13.[Abstract/Free Full Text]
- Fregley AR, Graybiel A. An ataxic test battery not requiring rails. Aerospace Med.. 1968;39:277-282.[Medline]
- Brauer SG, Burns Y, Galley P. Postural stability measures predict falls in community-dwelling elderly. J Gerontol A Biol Sci Med Sci.. 2000;55A:M469-M476.[Abstract/Free Full Text]
- Maki BE, Edmonstone MA, McIlroy.. Age-related differences in laterally directed compensatory stepping behavior. J Gerontol A Biol Sci Med Sci.. 2000;55A:M270-M277.[Abstract/Free Full Text]
- Nitz J, Low Choy N, Isles R. Medio-lateral postural stability in community dwelling women over 40 years of age. Clin Rehabil. In press.
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Abstract
Methods
