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Lifespan data on postural balance in multiple standing positions
Gait & Posture 76 (2020) 68–73
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Full length article
Lifespan data on postural balance in multiple standing positions a,
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J. Riis *, F. Eika , A.W. Blomkvist , M.T. Rahbek , K.D. Eikhof , M.D. Hansen , M. Søndergaard , J. Rygb,e, S. Andersena,d, M.G. Jorgensena a
Department of Geriatric Medicine, Aalborg University Hospital, Denmark Department of Geriatric Medicine, Odense University Hospital, Denmark School of Nursing, University College of Northern Denmark, Aalborg, Denmark d Department of Clinical Medicine, Aalborg University, Denmark e Department of Clinical Research, University of Southern, Denmark b c
A R T I C LE I N FO
A B S T R A C T
Keywords: Wii balance board Postural balance One-legged stance Reference data
Background: Maintaining balance is important throughout life. The Nintendo Wii Balance Board (WBB) can give reliable quantitative measures of postural balance, but reference data are lacking. Furthermore, one-leg standing balance across the adult lifespan is not fully described. The aim of the study was (1) to provide reference data on postural balance in multiple standing positions using a WBB, (2) to determine an age cut-off for the ability to stand on one-leg in men and women. Methods: This was a cross-sectional study and data was collected in two cities in Denmark (Aalborg and Odense) and Norway (Oslo and Ålesund) during spring and summer of 2016. Postural balance was assessed in individuals across the adult lifespan in three different bases of support positions (hip-wide and narrow two-legged stance, and one-legged stance) using a WBB. Reference data were analyzed and presented in 10-year intervals. Results: A total of 354 individuals aged 20–99 years were recruited. Reference data were presented in percentiles stratified by gender for the following age categories: 20–29, 30–39, 40–49, 50–59, 60–69, 70–79, and 80+. Data showed that the difference between men and women’s balance was larger at older age with men performing worst. The cut-off ability to stand on one-leg was 72.5 years without statistical evidence of gender difference. Conclusion: This study reports reference data for postural balance across the entire adult lifespan using a WBB. More than half of the individuals over 72.5 years of age were unable to stand balanced on one-leg.
1. Introduction Postural balance and stability plays an integral role in daily activities throughout life ranging from dynamic movements like walking, sports activities, and vacuum cleaning, to static movements like sitting in a chair [1,2]. Several physiological systems change with age (including the somatosensory, central nervous, and muscular systems) [3] leading to impaired postural balance (from here on denoted as: balance). These changes combined with an age-related lower activity level lead to greater postural sway [4] and increased fall risk [5]. Fortunately, poor balance might be reversible and previous studies have shown that only a few weeks of challenging balance interventions can improve balance in a clinically meaningful way [6,7]. Balance can be assessed using either subjective functional balance tests such as Berg Balance Scale, Timed Up and Go, and Five Timed Chair Stand Test, or objective measures such as force plate analysis
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[5,8]. Both approaches are used in research- and clinical- settings. The subjective measures are somewhat crude, yielding crude outcomes with large inter-rater variability, while the force plate technique is expensive, immobile, and can be difficult to operate [5]. Hence, the use of force plates has been limited to large institutions such as universities and hospitals, and large scale clinical implementation has not occurred [5,8,9]. Because of these limitations, clinicians have often favored the traditional functional balance tests to identify balance pathology or to measure progression in rehabilitation of their patients. So far, reference data on balance has been reported using traditional force plate measures [1,10–12]. These studies have only assessed balance during two-legged standing positions or in selected cohorts. In recent years, a new opportunity for large-scale implementation of the force plate technique has emerged with the introduction of the Nintendo Wii Balance Board (WBB) that produces measurements comparable to an expensive force plate [13]. The WBB was designed as a
Corresponding author at: Department of Geriatrics, Aalborg University Hospital, Hobrovej 18-22, 9000, Aalborg, Denmark. E-mail address: [email protected] (J. Riis).
https://doi.org/10.1016/j.gaitpost.2019.11.004 Received 29 June 2019; Received in revised form 6 October 2019; Accepted 6 November 2019 0966-6362/ © 2019 Elsevier B.V. All rights reserved.
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experimental procedure was initialized by gathering information on participants age, gender, weight, height, leg dominance (participants were asked which foot they would preferably use to kick a ball), smoking status, number of prescription drugs used daily, and physical activity at work and during leisure (International Physical Activity Questionnaire (IPAQ)) [17]. This was followed by measurements of balance, strength, and reaction time in the presented order using the WBB. Reference data on strength and reaction time has been published previously [13,18].
controller for exercise-based console gaming. Complimentary to its original design the WBB has gained interest as a reliable measurement tool for several physical parameters including muscle strength, reaction time, and balance [8,13,14]. Additionally, the WBB holds the advantage of being portable, inexpensive, and readily accessible. To our knowledge, no studies have so far reported reference data on balance using the WBB. This led us to produce reference balance data using the WBB in a large sample of men and women aged 20–99 years during three different base-of-support positions (one-legged stance, wide and narrow two-legged stance). In addition, we determined a cut-off age where 50 % of men and women were no longer capable of completing a 30 s onelegged stance test.
2.4. Postural balance procedure Balance was tested in three different base-of-support positions in the following order: hip-wide and narrow (toe against toe and heel against heel) two-legged stance and one-legged stance (dominant and nondominant leg). The duration of each measurement was 30 s. For the two two-legged tests this meant 3 × 30 s and for the one-legged test this meant 3 × 30 s for both the dominant and the non-dominant leg. Prior to and during recordings, participants were asked to stand as still as possible and maintain visual focus on a visual target two meters away at eye height. An additional recording was performed if participants changed standing position, lost visual focus, or their contralateral foot touched the ground during recordings. Participants who could not maintain one-legged stance for 30 s had no data collected in this position.
2. Methods 2.1. Study design & population This was a cross-sectional study and data was collected in two cities in Denmark (Aalborg and Odense) and Norway (Oslo and Ålesund) during spring and summer of 2016. Data was collected by six different healthcare professionals (medical doctors, nurses, and physiotherapists). Alignment of procedures was ensured by a training session at the Department of Geriatric Medicine, Aalborg University Hospital with all data collectors prior to initiation of data collection. To prevent operator bias, each operator was responsible for collecting data on seven to nine individuals from each of the seven age groups: 20–29, 30–39, 40–49, 50–59, 60–69, 70–79, and 80+ years of age. Each assessor collected data in the same site ensuring equal age distribution across sites. Participants were recruited at various locations (e.g. university campus, malls, hospital staff, and senior citizen clubs). Participants were eligible for inclusion if they were ≥20 years of age and considered themselves healthy and free from acute illness. Exclusion criteria were apparent cognitive impairment (i.e. could not name present year or capital of Denmark or Norway), inability to stand unsupported for 30 s, neuromuscular deficits (e.g. Parkinsons disease, myastenia gravis, sequela after stroke, or severe polyneuropathy), or musculoskeletal disease (e.g fracture or orthophedic surgery within 6 months, alloplastic surgery within 2 years, muscular dystrophy, or polymyositis rheumatica).
2.5. Statistical methods Baseline characteristics were reported according to the seven age groups (20–29, 30–39, 40–49, 50–59, 60–69, 70–79, 80+) stratified by gender. The two variables COP speed and COP area were extracted from the FysioMeter® software from each participant. COP speed and area were extracted for four different modes of stance: hip-wide two-legged stance, narrow two-legged stance, as well as dominant and non-dominant one-legged stance. Outliers were assessed using the outlier labelling rule and winsorized except for extreme outliers suspected to be measurement errors. The balance variables were reported as medians and < 10th, 10th–25th, 25th–75th, 75th–90th, and > 90th percentile intervals for the age and gender groups. The relationships between the balance variables and age on a continuous scale were assessed using restricted cubic splines with three knots at the 10th, 50th, and 90th percentiles based on linear regression. Restricted cubic splines were used as age was non-normally distributed and to assess non-linear relations [19]. To evaluate the age at which participants were unable to perform the one-legged stance test, the probability of test failure as a function of age based on a logistic regression model was visualized with a restricted cubic spline with three knots at the 10th, 50th, and 90th percentiles. A cut-off age at 50 % probability of test failure was estimated. Likelihood ratio tests were performed for all models to assess gender difference and interaction between age and gender. The linear regression models showed gender difference and one model showed significant evidence of interaction. All curves based on linear regression models were stratified by gender. The difference in one-legged COP speed between the dominant and non-dominant legwas assessed by one-sample t-tests and gender difference was assessed by ANOVA.
2.2. Equipment and software The WBB (Nintendo, Kyoto, Japan) is a small portable force plate with uniaxial vertical strain gauge transducers positioned in each of the four corners. Data from the WBB was collected at approximately 100 Hz from each transducer and transferred via Bluetooth to a personal computer. Data was uploaded to the FysioMeter® software (Bronderslev, Denmark) and filtered using a 4th order Butterworth filter with a cut-off frequency of 20 Hz to remove unwanted frequencies. The FysioMeter® software calculated two variables: mean sway speed (center of pressure (COP) speed) in mm/s and sway ellipse area (COP area) in mm2. Sway speed was computed by taking total path length divided by test time (30 s). Sway ellipse area was determined by the standard ellipse area method [15]. The WBB has excellent validity compared to force plates in high quality studies (intraclass correlation 0.74–0.99) [14]. To quantify accuracy, we have taken the average of the mediolateral and anteroposterior uncertainty reported by Bartlett et al. [16]. This gives the WBB an uncertainty for COP displacement of 3.8 mm compared to 4.1 mm for an AMTI force plate. Bartlett et al. did not find any significant differences between the WBB and the AMTI force plate [16].
2.6. Ethics The need for ethical approval was waived by the ethics committee of the North Jutland Region. Consent was obtained from all participants before participation in the study.
2.3. Overall experimental procedure All measurements were performed during a single session. The 69
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Table 1 Baseline Characteristics of the Study Population. BMI is reported as median [25th percentile, 75th percentile] due to non-normality. Medicine refers to number of drugs used daily. Physical activity at work and during leisure was reported on a scale of 1 (least active) to 4 (most active). *past retirement age. **presented as medians. Age (Groups)
20-29 30-39 40-49 50-59 60-69 70-79 80+
Gender (n)
36 22 30 15 21 20 30 16 35 19 33 20 25 32
Women Men Women Men Women Men Women Men Women Men Women Men Women Men
BMI (kg/m2)
21.6 24.5 24.3 25.0 26.9 26.6 25.0 26.3 26.4 26.5 25.6 26.1 25.6 26.9
[20.3, [23.3, [21.0, [24.1, [23.1, [24.0, [22.6, [24.2, [22.7, [24.9, [23.8, [24.4, [21.8, [25.0,
24.1] 25.9] 29.9] 26.0] 29.4] 29.1] 28.3] 27.8] 28.9] 33.7] 30.1] 27.2] 27.6] 29.3]
Medicine (n) **
0 0 0 0 0 0 1 0 1 0 1 3 3 1
Smoking (%)
Physical activity**
Never
Current
Prior
Work
Home
89 86 80 73 67 55 53 63 60 42 64 35 52 44
3 9 10 27 24 45 23 19 29 47 33 50 48 60
8 5 10 0 10 0 23 19 11 11 3 5 0 6
2 2 2 2 2.5 2 2 2.5 3 2 * * * *
3 3 2.5 3 3 3 2 3 3 3 2 2 3 3
3. Results 3.1. Baseline characteristics A total of 354 participants between the age of 20–99 years were included in the study. Baseline characteristics of the study-population are presented in Table 1. Older participants were more likely to smoke and take medications, and older men were more likely to smoke than older women. Across age groups there was a moderate to high level of physical activity.
3.2. Two-legged stance (hip-wide) Fig. 2. Narrow Stance Center of Pressure Speed by Age and Gender. Restricted cubic splines of COP speed for narrow two-legged stance stratified by gender. Knots were placed at the 10th, 50th and 90th percentiles. Abbreviations; W: women; M: men.
Fig. 1 shows that men aged 20–40 years have lower COP speed than women. With increasing age men show a greater increment in COP speed than women, eventually resulting in men having greater COP speed during hip-wide stance (p for interaction = 0.02). Results for COP area can be found in Supplementary Fig. 1 and generally follows the same age-related increase as COP speed. This model showed no evidence of interaction (p = 0.16). But there was still statistical support of gender difference (p = 0.02). Reference data tables of medians and < 10th, 10th–25th, 25th–75th, 75th–90th, and > 90th percentile intervals for COP speed and area during hip-wide stance for women and men can be found in Supplementary Tables 1 and 2, respectively.
3.3. Two-legged stance (narrow) Fig. 2 shows COP speed by age as a continuous variable for narrow stance stratified by gender. The effect of age on balance during narrow stance corresponded to the effect during hip-wide stance with values of COP speed increasing with age. Men had greater COP speed than women (p = 0.03). The figure shows that men have a steeper incline in COP speed than women, but this was not significant (p = 0.21). Results for COP area can be found in Supplementary Fig. 2, which shows a similar development with age between genders (p for interaction = 0.44) with men having higher COP area (p = 0.001). Reference data tables of medians and < 10th, 10th–25th, 25th–75th, 75th–90th, and > 90th percentile intervals for COP speed and area during narrow stance for women and men can be found in Supplementary Tables 3 and 4.
3.4. One-legged stance 3.4.1. Age and the ability to perform one-legged stance A total of 238 (67 %) participants were able to perform the onelegged stance test. Of these, 145 were women and 93 were men. Fig. 3 shows COP speed by age as a continuous variable for onelegged stance stratified by leg and gender. Men had higher values of COP speed than women for both the dominant (p < 0.001) and nondominant (p < 0.001) leg with similar age-related difference (p = 0.13 for the dominant leg and p = 0.12 for the non-dominant leg).
Fig. 1. Hip-Wide Stance Center of Pressure Speed by Age and Gender. Restricted cubic splines of center of pressure speed for hip-wide two-legged stance stratified by gender. Knots were placed at the 10th, 50th, and 90th percentiles. Abbreviations; COP: center of pressure; W: women; M: men. 70
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In addition, we found that the 50 % cut-off age of being able to perform the one-legged balance test was 72.5 years. Finally, we found no statistical difference in balance between the dominant and non-dominant leg in both men and women. Our results showed that balance in both men and women deteriorated with advancing age – this is not surprising and in line with previous findings [21]. Further, the rate of decline in balance with age was likewise similar to findings in two large studies with 7979 and 16,357 participants [1,22]. We also found that men performed worse than women in both hip-wide and narrow standing positions and had a steeper decline in hip-wide COP speed with age. This gender difference has previously been observed during two-legged stance in numerous studies using force platforms [1,10,11,22]. This superior balance performance in women is conflicting with other physiological findings, as women tend to have lower muscle strength [23], slower reaction time [13], poorer performance in functional balance tests [24], and higher fall rates [25] compared to men. A possible explanation for the worse balance performance in men compared to women is a difference in the vibrotactile threshold. The vibrotactile threshold can generally be used as a measure of peripheral nervous sensory function and the vibrotactile threshold of the feet is arguably an important determinant of balance performance [1,10]. Observational studies [26,27] have shown that men experience a larger increase in vibrotactile threshold with age than women, indication worse peripheral sensory function in older men than in older women. The current study provided reference data across the entire adult lifespan on balance during one-legged stance using quantitative measures of COP movement. Our data showed that men had lower onelegged balance than women. There was a trend towards a greater between gender difference with age (see Fig. 3), but this was not significant. Previous studies have mainly focused on two-legged stance, selected age groups, or only women [1,11,12,28]. Therefore, we could only compare our results to a reference study which only included women. The study recorded one-legged balance in 453 women between 20 and 80 years [12] and found that women in their seventies had 11.2 times greater one-legged COP speed compared to women in their twenties. This is very different from our study, where women in their seventies only had a 1.9 times higher COP speed than women in their twenties. This discrepancy might be attributed to differences in studypopulations or because of different measurement methods in the two studies. The study only focusing on women tested participants for 3 × 10 s [12] while we performed 3 × 30 s tests. Thus, they may have included more participants with poor balance in their assessment - as most people over the age of 70 are unable to perform 30 s of one-legged stance, as found in our study (Fig. 4). Therefore, the reference data we present on WBB force plate measures of one-legged balance should only be used for 30 s stance test, as the impact of test duration on reference values, especially in older adults, can be very large [29]. More studies are needed using the 30 s force plate measurements of one-legged balance to externally validate the age-related and between-gender differences found in this study. We reported a 50 % age cut-off of 72.5 years on the 30 s one-leg stance test. While we found no studies of 50 % age cut-off for 30 s of one-legged stance, our results are in line with the results of Morioka et al. [29] who tested maximum one-leg standing time in 1241 men and women between 2 and 92 years. Morioka et al. showed that mean standing time decreased from from 60 s for participants aged 60–70 years to 30 s for participants aged 70-80. Thus, it is shown in both our study and the study by Morioka et al. [29] that the ability to perform one-legged stance undergoes an accelerated decline from around the age of 60 years and onwards. This change around the age of retirement could be explained by both physiological changes related to aging and/ or behavioral changes related to a more sedentary lifestyle following retirement. While alike, the two assessments (one leg standing time vs. force plate balance) focus on two different aspects of balance; the force plate gives an assessment of sway and a greater sway also suggest a
Fig. 3. One-Legged Stance Center of Pressure Speed by Leg, Age, and Gender. Restricted cubic splines of center of pressure speed for one-legged stance by leg and gender. Solid lines and dots represent the dominant leg, whereas the dotted lines and plus signs represents the non-dominant leg. Knots were placed at the 10th, 50th and 90th percentiles. Abbreviations; COP: center of pressure; W: women; M: men.
Reference data tables of medians and < 10th, 10th–25th, 25th–75th, 75th–90th, and > 90th percentile intervals for COP speed and area by gender for the dominant and non-dominant leg can be found in Supplementary Tables 5 and 6. Fig. 4 shows the probability of failure of the one-legged stance test based on age. The cut-off age at which 50 % were not able to perform the one-legged stance test was 72.5 years without evidence of gender difference or interaction (p = 0.98 and p = 0.49, respectively). 3.4.2. Influence of leg dominance on postural balance during one-legged stance There was no significant difference between legs with mean leg differences in COP speed of 0.89 % (p = 0.32) favouring non-dominant leg and leg difference was not affected by gender (p = 0.87). This is also illustrated in Fig. 3. 4. Discussion This study reported reference values of balance using a WBB in a population of 354 individuals between 20 and 99 years. This is the first report of reference data on balance using a WBB. Our results showed that older individuals have worse balance than younger individuals, and that men had similar or worse balance than women in all standing positions. We interpret greater COP area and higher speed values as indicators of poorer balance as they predict falls and other outcomes related to poor balance [5,8]. This interpretation is not universally accepted as it is not consistently showed in all patient subgroups [5,20].
Fig. 4. Age and the Probability of not being able to Stand on one Leg. Restricted cubic spline showing 50 % cut-off at 69 years (men) and 73.5 years (women). Knots were placed at the 10th, 50th and 90th percentiles. Abbreviations; W: women; M: men. 71
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References
greater number of near balance losses during stance, while one-legged standing time is more of an endurance test. Further research is needed in order to address which of these assessments are best in a given situation. Finally, we showed no difference in balance performance between the dominant and non-dominant leg. This is in accordance with previous findings from a smaller study (n = 30) which assessed balance difference between legs in healthy young adults [30]. The lack of leg dominance in balance performance is unsurprising when considering that the most common activities involving the lower limbs, like walking and running, are not characterized by leg dominance. Also, Matsuda et al. [31] compared 17 soccer players with 17 untrained students but still found no difference between legs. A limitation of our study is the fact that we only assessed static and not dynamic balance, which is more relevant during measures of daily activity. Further, our assessments of daily physical activity using only four categories may not be detailed enough to fully evaluate differences across age groups. Also, as the Danish population is very ethnically homogeneous our findings will need to be validated in other populations. We cannot rule out the possibility that some participants had medical conditions such as undiagnosed neuropathy or visual impairment affecting balance as no formal screening for these conditions was performed. Finally, it is possible that differences in environments at test sites (lighting, visual surrounding etc.) may affect COP measures and age-related comparisons as age may be differently distributed across sites. We found evidence of greater balance difference between men and women with age (interaction). Our study is cross-sectional, so whether this is due to a higher rate of decline in men than women should be investigated in a study with longitudinal design which is the proper design to investigate this hypothesis. This study also has some strengths; it has a relatively large sample size across the entire adult lifespan, and we considered balance during several different standing positions. Further, our sampling method ensured a similar number of participants in each age group.
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5. Conclusion This study provided novel reference data on balance using a WBB during various standing positions. Further, we report a cut-off age of 72.5 years at which 50 % are unable to complete a 30 s one-leg standing time test. Finally, we showed that there is no difference in balance between the dominant leg and the non-dominant leg for both men and women. The reported results contribute to increased understanding of the aging process of balance in both men and women and can used in clinical practice as wells as research. All authors have nothing to declare except for one author (MGJ), who is a shareholder of FysioMeter. However, MGJ was held out of the data collection and statistical analysis. Declaration of Competing Interest All authors have nothing to declare except for one author (MGJ), who is a shareholder of FysioMeter. However, MGJ was held out of the data collection and statistical analysis. Acknowledgement This study was funded by the Department of Geriatric Medicine, Aalborg University Hospital. Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.gaitpost.2019.11.004. 72
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differences in time-limit performance and force platform-based balance measures during one-leg stance, J. Electromyogr. Kinesiol. 23 (2013) 634–639, https://doi. org/10.1016/j.jelekin.2013.01.008. [29] S. Morioka, T. Fukumoto, M. Hiyamizu, A. Matsuo, H. Takebayashi, K. Miyamoto, Changes in the equilibrium of standing on one leg at various life stages, Curr. Gerontol. Geriatr. Res. 2012 (2012) 1–6, https://doi.org/10.1155/2012/516283. [30] T. Muehlbauer, A. Gollhofer, U. Granacher, Associations between measures of balance and lower-extremity muscle strength/power in healthy individuals across the lifespan: a systematic review and meta-analysis, Sports Med. 45 (2015) 1671–1692, https://doi.org/10.1007/s40279-015-0390-z. [31] S. Matsuda, S. Demura, Y. Nagasawa, Static one-legged balance in soccer players during use of a lifted leg, Percept. Mot. Skills 111 (2010) 167–177, https://doi.org/ 10.2466/05.23.26.27.PMS.111.4.167-177.
community-dwelling elderly people: six-minute walk test, Berg balance scale, timed up & go test, and gait speeds, Phys. Ther. 82 (2002) 128–137 (accessed January 3, 2019), http://www.ncbi.nlm.nih.gov/pubmed/11856064. A.F. Ambrose, G. Paul, J.M. Hausdorff, Risk factors for falls among older adults: a review of the literature, Maturitas. 75 (2013) 51–61, https://doi.org/10.1016/j. maturitas.2013.02.009. P. Halonen, Quantitative vibration perception thresholds in healthy subjects of working age, Eur. J. Appl. Physiol. Occup. Physiol. 54 (1986) 647–655 (accessed January 3, 2019), http://www.ncbi.nlm.nih.gov/pubmed/3948860. L. Venkatesan, S.M. Barlow, D. Kieweg, Age- and sex-related changes in vibrotactile sensitivity of hand and face in neurotypical adults, Somatosens. Mot. Res. 32 (2015) 44–50, https://doi.org/10.3109/08990220.2014.958216. R.A. da Silva, M. Bilodeau, R.B. Parreira, D.C. Teixeira, C.F. Amorim, Age-related
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Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Full length article
Lifespan data on postural balance in multiple standing positions a,
a
a
b
c
a
T a
J. Riis *, F. Eika , A.W. Blomkvist , M.T. Rahbek , K.D. Eikhof , M.D. Hansen , M. Søndergaard , J. Rygb,e, S. Andersena,d, M.G. Jorgensena a
Department of Geriatric Medicine, Aalborg University Hospital, Denmark Department of Geriatric Medicine, Odense University Hospital, Denmark School of Nursing, University College of Northern Denmark, Aalborg, Denmark d Department of Clinical Medicine, Aalborg University, Denmark e Department of Clinical Research, University of Southern, Denmark b c
A R T I C LE I N FO
A B S T R A C T
Keywords: Wii balance board Postural balance One-legged stance Reference data
Background: Maintaining balance is important throughout life. The Nintendo Wii Balance Board (WBB) can give reliable quantitative measures of postural balance, but reference data are lacking. Furthermore, one-leg standing balance across the adult lifespan is not fully described. The aim of the study was (1) to provide reference data on postural balance in multiple standing positions using a WBB, (2) to determine an age cut-off for the ability to stand on one-leg in men and women. Methods: This was a cross-sectional study and data was collected in two cities in Denmark (Aalborg and Odense) and Norway (Oslo and Ålesund) during spring and summer of 2016. Postural balance was assessed in individuals across the adult lifespan in three different bases of support positions (hip-wide and narrow two-legged stance, and one-legged stance) using a WBB. Reference data were analyzed and presented in 10-year intervals. Results: A total of 354 individuals aged 20–99 years were recruited. Reference data were presented in percentiles stratified by gender for the following age categories: 20–29, 30–39, 40–49, 50–59, 60–69, 70–79, and 80+. Data showed that the difference between men and women’s balance was larger at older age with men performing worst. The cut-off ability to stand on one-leg was 72.5 years without statistical evidence of gender difference. Conclusion: This study reports reference data for postural balance across the entire adult lifespan using a WBB. More than half of the individuals over 72.5 years of age were unable to stand balanced on one-leg.
1. Introduction Postural balance and stability plays an integral role in daily activities throughout life ranging from dynamic movements like walking, sports activities, and vacuum cleaning, to static movements like sitting in a chair [1,2]. Several physiological systems change with age (including the somatosensory, central nervous, and muscular systems) [3] leading to impaired postural balance (from here on denoted as: balance). These changes combined with an age-related lower activity level lead to greater postural sway [4] and increased fall risk [5]. Fortunately, poor balance might be reversible and previous studies have shown that only a few weeks of challenging balance interventions can improve balance in a clinically meaningful way [6,7]. Balance can be assessed using either subjective functional balance tests such as Berg Balance Scale, Timed Up and Go, and Five Timed Chair Stand Test, or objective measures such as force plate analysis
⁎
[5,8]. Both approaches are used in research- and clinical- settings. The subjective measures are somewhat crude, yielding crude outcomes with large inter-rater variability, while the force plate technique is expensive, immobile, and can be difficult to operate [5]. Hence, the use of force plates has been limited to large institutions such as universities and hospitals, and large scale clinical implementation has not occurred [5,8,9]. Because of these limitations, clinicians have often favored the traditional functional balance tests to identify balance pathology or to measure progression in rehabilitation of their patients. So far, reference data on balance has been reported using traditional force plate measures [1,10–12]. These studies have only assessed balance during two-legged standing positions or in selected cohorts. In recent years, a new opportunity for large-scale implementation of the force plate technique has emerged with the introduction of the Nintendo Wii Balance Board (WBB) that produces measurements comparable to an expensive force plate [13]. The WBB was designed as a
Corresponding author at: Department of Geriatrics, Aalborg University Hospital, Hobrovej 18-22, 9000, Aalborg, Denmark. E-mail address: [email protected] (J. Riis).
https://doi.org/10.1016/j.gaitpost.2019.11.004 Received 29 June 2019; Received in revised form 6 October 2019; Accepted 6 November 2019 0966-6362/ © 2019 Elsevier B.V. All rights reserved.
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experimental procedure was initialized by gathering information on participants age, gender, weight, height, leg dominance (participants were asked which foot they would preferably use to kick a ball), smoking status, number of prescription drugs used daily, and physical activity at work and during leisure (International Physical Activity Questionnaire (IPAQ)) [17]. This was followed by measurements of balance, strength, and reaction time in the presented order using the WBB. Reference data on strength and reaction time has been published previously [13,18].
controller for exercise-based console gaming. Complimentary to its original design the WBB has gained interest as a reliable measurement tool for several physical parameters including muscle strength, reaction time, and balance [8,13,14]. Additionally, the WBB holds the advantage of being portable, inexpensive, and readily accessible. To our knowledge, no studies have so far reported reference data on balance using the WBB. This led us to produce reference balance data using the WBB in a large sample of men and women aged 20–99 years during three different base-of-support positions (one-legged stance, wide and narrow two-legged stance). In addition, we determined a cut-off age where 50 % of men and women were no longer capable of completing a 30 s onelegged stance test.
2.4. Postural balance procedure Balance was tested in three different base-of-support positions in the following order: hip-wide and narrow (toe against toe and heel against heel) two-legged stance and one-legged stance (dominant and nondominant leg). The duration of each measurement was 30 s. For the two two-legged tests this meant 3 × 30 s and for the one-legged test this meant 3 × 30 s for both the dominant and the non-dominant leg. Prior to and during recordings, participants were asked to stand as still as possible and maintain visual focus on a visual target two meters away at eye height. An additional recording was performed if participants changed standing position, lost visual focus, or their contralateral foot touched the ground during recordings. Participants who could not maintain one-legged stance for 30 s had no data collected in this position.
2. Methods 2.1. Study design & population This was a cross-sectional study and data was collected in two cities in Denmark (Aalborg and Odense) and Norway (Oslo and Ålesund) during spring and summer of 2016. Data was collected by six different healthcare professionals (medical doctors, nurses, and physiotherapists). Alignment of procedures was ensured by a training session at the Department of Geriatric Medicine, Aalborg University Hospital with all data collectors prior to initiation of data collection. To prevent operator bias, each operator was responsible for collecting data on seven to nine individuals from each of the seven age groups: 20–29, 30–39, 40–49, 50–59, 60–69, 70–79, and 80+ years of age. Each assessor collected data in the same site ensuring equal age distribution across sites. Participants were recruited at various locations (e.g. university campus, malls, hospital staff, and senior citizen clubs). Participants were eligible for inclusion if they were ≥20 years of age and considered themselves healthy and free from acute illness. Exclusion criteria were apparent cognitive impairment (i.e. could not name present year or capital of Denmark or Norway), inability to stand unsupported for 30 s, neuromuscular deficits (e.g. Parkinsons disease, myastenia gravis, sequela after stroke, or severe polyneuropathy), or musculoskeletal disease (e.g fracture or orthophedic surgery within 6 months, alloplastic surgery within 2 years, muscular dystrophy, or polymyositis rheumatica).
2.5. Statistical methods Baseline characteristics were reported according to the seven age groups (20–29, 30–39, 40–49, 50–59, 60–69, 70–79, 80+) stratified by gender. The two variables COP speed and COP area were extracted from the FysioMeter® software from each participant. COP speed and area were extracted for four different modes of stance: hip-wide two-legged stance, narrow two-legged stance, as well as dominant and non-dominant one-legged stance. Outliers were assessed using the outlier labelling rule and winsorized except for extreme outliers suspected to be measurement errors. The balance variables were reported as medians and < 10th, 10th–25th, 25th–75th, 75th–90th, and > 90th percentile intervals for the age and gender groups. The relationships between the balance variables and age on a continuous scale were assessed using restricted cubic splines with three knots at the 10th, 50th, and 90th percentiles based on linear regression. Restricted cubic splines were used as age was non-normally distributed and to assess non-linear relations [19]. To evaluate the age at which participants were unable to perform the one-legged stance test, the probability of test failure as a function of age based on a logistic regression model was visualized with a restricted cubic spline with three knots at the 10th, 50th, and 90th percentiles. A cut-off age at 50 % probability of test failure was estimated. Likelihood ratio tests were performed for all models to assess gender difference and interaction between age and gender. The linear regression models showed gender difference and one model showed significant evidence of interaction. All curves based on linear regression models were stratified by gender. The difference in one-legged COP speed between the dominant and non-dominant legwas assessed by one-sample t-tests and gender difference was assessed by ANOVA.
2.2. Equipment and software The WBB (Nintendo, Kyoto, Japan) is a small portable force plate with uniaxial vertical strain gauge transducers positioned in each of the four corners. Data from the WBB was collected at approximately 100 Hz from each transducer and transferred via Bluetooth to a personal computer. Data was uploaded to the FysioMeter® software (Bronderslev, Denmark) and filtered using a 4th order Butterworth filter with a cut-off frequency of 20 Hz to remove unwanted frequencies. The FysioMeter® software calculated two variables: mean sway speed (center of pressure (COP) speed) in mm/s and sway ellipse area (COP area) in mm2. Sway speed was computed by taking total path length divided by test time (30 s). Sway ellipse area was determined by the standard ellipse area method [15]. The WBB has excellent validity compared to force plates in high quality studies (intraclass correlation 0.74–0.99) [14]. To quantify accuracy, we have taken the average of the mediolateral and anteroposterior uncertainty reported by Bartlett et al. [16]. This gives the WBB an uncertainty for COP displacement of 3.8 mm compared to 4.1 mm for an AMTI force plate. Bartlett et al. did not find any significant differences between the WBB and the AMTI force plate [16].
2.6. Ethics The need for ethical approval was waived by the ethics committee of the North Jutland Region. Consent was obtained from all participants before participation in the study.
2.3. Overall experimental procedure All measurements were performed during a single session. The 69
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Table 1 Baseline Characteristics of the Study Population. BMI is reported as median [25th percentile, 75th percentile] due to non-normality. Medicine refers to number of drugs used daily. Physical activity at work and during leisure was reported on a scale of 1 (least active) to 4 (most active). *past retirement age. **presented as medians. Age (Groups)
20-29 30-39 40-49 50-59 60-69 70-79 80+
Gender (n)
36 22 30 15 21 20 30 16 35 19 33 20 25 32
Women Men Women Men Women Men Women Men Women Men Women Men Women Men
BMI (kg/m2)
21.6 24.5 24.3 25.0 26.9 26.6 25.0 26.3 26.4 26.5 25.6 26.1 25.6 26.9
[20.3, [23.3, [21.0, [24.1, [23.1, [24.0, [22.6, [24.2, [22.7, [24.9, [23.8, [24.4, [21.8, [25.0,
24.1] 25.9] 29.9] 26.0] 29.4] 29.1] 28.3] 27.8] 28.9] 33.7] 30.1] 27.2] 27.6] 29.3]
Medicine (n) **
0 0 0 0 0 0 1 0 1 0 1 3 3 1
Smoking (%)
Physical activity**
Never
Current
Prior
Work
Home
89 86 80 73 67 55 53 63 60 42 64 35 52 44
3 9 10 27 24 45 23 19 29 47 33 50 48 60
8 5 10 0 10 0 23 19 11 11 3 5 0 6
2 2 2 2 2.5 2 2 2.5 3 2 * * * *
3 3 2.5 3 3 3 2 3 3 3 2 2 3 3
3. Results 3.1. Baseline characteristics A total of 354 participants between the age of 20–99 years were included in the study. Baseline characteristics of the study-population are presented in Table 1. Older participants were more likely to smoke and take medications, and older men were more likely to smoke than older women. Across age groups there was a moderate to high level of physical activity.
3.2. Two-legged stance (hip-wide) Fig. 2. Narrow Stance Center of Pressure Speed by Age and Gender. Restricted cubic splines of COP speed for narrow two-legged stance stratified by gender. Knots were placed at the 10th, 50th and 90th percentiles. Abbreviations; W: women; M: men.
Fig. 1 shows that men aged 20–40 years have lower COP speed than women. With increasing age men show a greater increment in COP speed than women, eventually resulting in men having greater COP speed during hip-wide stance (p for interaction = 0.02). Results for COP area can be found in Supplementary Fig. 1 and generally follows the same age-related increase as COP speed. This model showed no evidence of interaction (p = 0.16). But there was still statistical support of gender difference (p = 0.02). Reference data tables of medians and < 10th, 10th–25th, 25th–75th, 75th–90th, and > 90th percentile intervals for COP speed and area during hip-wide stance for women and men can be found in Supplementary Tables 1 and 2, respectively.
3.3. Two-legged stance (narrow) Fig. 2 shows COP speed by age as a continuous variable for narrow stance stratified by gender. The effect of age on balance during narrow stance corresponded to the effect during hip-wide stance with values of COP speed increasing with age. Men had greater COP speed than women (p = 0.03). The figure shows that men have a steeper incline in COP speed than women, but this was not significant (p = 0.21). Results for COP area can be found in Supplementary Fig. 2, which shows a similar development with age between genders (p for interaction = 0.44) with men having higher COP area (p = 0.001). Reference data tables of medians and < 10th, 10th–25th, 25th–75th, 75th–90th, and > 90th percentile intervals for COP speed and area during narrow stance for women and men can be found in Supplementary Tables 3 and 4.
3.4. One-legged stance 3.4.1. Age and the ability to perform one-legged stance A total of 238 (67 %) participants were able to perform the onelegged stance test. Of these, 145 were women and 93 were men. Fig. 3 shows COP speed by age as a continuous variable for onelegged stance stratified by leg and gender. Men had higher values of COP speed than women for both the dominant (p < 0.001) and nondominant (p < 0.001) leg with similar age-related difference (p = 0.13 for the dominant leg and p = 0.12 for the non-dominant leg).
Fig. 1. Hip-Wide Stance Center of Pressure Speed by Age and Gender. Restricted cubic splines of center of pressure speed for hip-wide two-legged stance stratified by gender. Knots were placed at the 10th, 50th, and 90th percentiles. Abbreviations; COP: center of pressure; W: women; M: men. 70
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In addition, we found that the 50 % cut-off age of being able to perform the one-legged balance test was 72.5 years. Finally, we found no statistical difference in balance between the dominant and non-dominant leg in both men and women. Our results showed that balance in both men and women deteriorated with advancing age – this is not surprising and in line with previous findings [21]. Further, the rate of decline in balance with age was likewise similar to findings in two large studies with 7979 and 16,357 participants [1,22]. We also found that men performed worse than women in both hip-wide and narrow standing positions and had a steeper decline in hip-wide COP speed with age. This gender difference has previously been observed during two-legged stance in numerous studies using force platforms [1,10,11,22]. This superior balance performance in women is conflicting with other physiological findings, as women tend to have lower muscle strength [23], slower reaction time [13], poorer performance in functional balance tests [24], and higher fall rates [25] compared to men. A possible explanation for the worse balance performance in men compared to women is a difference in the vibrotactile threshold. The vibrotactile threshold can generally be used as a measure of peripheral nervous sensory function and the vibrotactile threshold of the feet is arguably an important determinant of balance performance [1,10]. Observational studies [26,27] have shown that men experience a larger increase in vibrotactile threshold with age than women, indication worse peripheral sensory function in older men than in older women. The current study provided reference data across the entire adult lifespan on balance during one-legged stance using quantitative measures of COP movement. Our data showed that men had lower onelegged balance than women. There was a trend towards a greater between gender difference with age (see Fig. 3), but this was not significant. Previous studies have mainly focused on two-legged stance, selected age groups, or only women [1,11,12,28]. Therefore, we could only compare our results to a reference study which only included women. The study recorded one-legged balance in 453 women between 20 and 80 years [12] and found that women in their seventies had 11.2 times greater one-legged COP speed compared to women in their twenties. This is very different from our study, where women in their seventies only had a 1.9 times higher COP speed than women in their twenties. This discrepancy might be attributed to differences in studypopulations or because of different measurement methods in the two studies. The study only focusing on women tested participants for 3 × 10 s [12] while we performed 3 × 30 s tests. Thus, they may have included more participants with poor balance in their assessment - as most people over the age of 70 are unable to perform 30 s of one-legged stance, as found in our study (Fig. 4). Therefore, the reference data we present on WBB force plate measures of one-legged balance should only be used for 30 s stance test, as the impact of test duration on reference values, especially in older adults, can be very large [29]. More studies are needed using the 30 s force plate measurements of one-legged balance to externally validate the age-related and between-gender differences found in this study. We reported a 50 % age cut-off of 72.5 years on the 30 s one-leg stance test. While we found no studies of 50 % age cut-off for 30 s of one-legged stance, our results are in line with the results of Morioka et al. [29] who tested maximum one-leg standing time in 1241 men and women between 2 and 92 years. Morioka et al. showed that mean standing time decreased from from 60 s for participants aged 60–70 years to 30 s for participants aged 70-80. Thus, it is shown in both our study and the study by Morioka et al. [29] that the ability to perform one-legged stance undergoes an accelerated decline from around the age of 60 years and onwards. This change around the age of retirement could be explained by both physiological changes related to aging and/ or behavioral changes related to a more sedentary lifestyle following retirement. While alike, the two assessments (one leg standing time vs. force plate balance) focus on two different aspects of balance; the force plate gives an assessment of sway and a greater sway also suggest a
Fig. 3. One-Legged Stance Center of Pressure Speed by Leg, Age, and Gender. Restricted cubic splines of center of pressure speed for one-legged stance by leg and gender. Solid lines and dots represent the dominant leg, whereas the dotted lines and plus signs represents the non-dominant leg. Knots were placed at the 10th, 50th and 90th percentiles. Abbreviations; COP: center of pressure; W: women; M: men.
Reference data tables of medians and < 10th, 10th–25th, 25th–75th, 75th–90th, and > 90th percentile intervals for COP speed and area by gender for the dominant and non-dominant leg can be found in Supplementary Tables 5 and 6. Fig. 4 shows the probability of failure of the one-legged stance test based on age. The cut-off age at which 50 % were not able to perform the one-legged stance test was 72.5 years without evidence of gender difference or interaction (p = 0.98 and p = 0.49, respectively). 3.4.2. Influence of leg dominance on postural balance during one-legged stance There was no significant difference between legs with mean leg differences in COP speed of 0.89 % (p = 0.32) favouring non-dominant leg and leg difference was not affected by gender (p = 0.87). This is also illustrated in Fig. 3. 4. Discussion This study reported reference values of balance using a WBB in a population of 354 individuals between 20 and 99 years. This is the first report of reference data on balance using a WBB. Our results showed that older individuals have worse balance than younger individuals, and that men had similar or worse balance than women in all standing positions. We interpret greater COP area and higher speed values as indicators of poorer balance as they predict falls and other outcomes related to poor balance [5,8]. This interpretation is not universally accepted as it is not consistently showed in all patient subgroups [5,20].
Fig. 4. Age and the Probability of not being able to Stand on one Leg. Restricted cubic spline showing 50 % cut-off at 69 years (men) and 73.5 years (women). Knots were placed at the 10th, 50th and 90th percentiles. Abbreviations; W: women; M: men. 71
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References
greater number of near balance losses during stance, while one-legged standing time is more of an endurance test. Further research is needed in order to address which of these assessments are best in a given situation. Finally, we showed no difference in balance performance between the dominant and non-dominant leg. This is in accordance with previous findings from a smaller study (n = 30) which assessed balance difference between legs in healthy young adults [30]. The lack of leg dominance in balance performance is unsurprising when considering that the most common activities involving the lower limbs, like walking and running, are not characterized by leg dominance. Also, Matsuda et al. [31] compared 17 soccer players with 17 untrained students but still found no difference between legs. A limitation of our study is the fact that we only assessed static and not dynamic balance, which is more relevant during measures of daily activity. Further, our assessments of daily physical activity using only four categories may not be detailed enough to fully evaluate differences across age groups. Also, as the Danish population is very ethnically homogeneous our findings will need to be validated in other populations. We cannot rule out the possibility that some participants had medical conditions such as undiagnosed neuropathy or visual impairment affecting balance as no formal screening for these conditions was performed. Finally, it is possible that differences in environments at test sites (lighting, visual surrounding etc.) may affect COP measures and age-related comparisons as age may be differently distributed across sites. We found evidence of greater balance difference between men and women with age (interaction). Our study is cross-sectional, so whether this is due to a higher rate of decline in men than women should be investigated in a study with longitudinal design which is the proper design to investigate this hypothesis. This study also has some strengths; it has a relatively large sample size across the entire adult lifespan, and we considered balance during several different standing positions. Further, our sampling method ensured a similar number of participants in each age group.
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5. Conclusion This study provided novel reference data on balance using a WBB during various standing positions. Further, we report a cut-off age of 72.5 years at which 50 % are unable to complete a 30 s one-leg standing time test. Finally, we showed that there is no difference in balance between the dominant leg and the non-dominant leg for both men and women. The reported results contribute to increased understanding of the aging process of balance in both men and women and can used in clinical practice as wells as research. All authors have nothing to declare except for one author (MGJ), who is a shareholder of FysioMeter. However, MGJ was held out of the data collection and statistical analysis. Declaration of Competing Interest All authors have nothing to declare except for one author (MGJ), who is a shareholder of FysioMeter. However, MGJ was held out of the data collection and statistical analysis. Acknowledgement This study was funded by the Department of Geriatric Medicine, Aalborg University Hospital. Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.gaitpost.2019.11.004. 72
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