Comparison of Postural Sways Between Younger and Older Adults Using a Triaxial Accelerometer in Quiet Standing: A Pilot Study
Perbandingan huyungan postur di antara golongan dewasa muda dan warga emas menggunakan accelerometer ketika berdiri statik: Kajian rintis
NOR NAJWATUL AKMAL AB RAHMAN, DEVINDER KAUR AJIT SINGH, SITI ZAFIRA BINTI ZAINAL ABIDIN, NOR HANIZA BINTI ABDUL WAHAT, SHAZARINA OTHMAN
& DEEPASHINI HARITHASAN
ABSTRACTThe measure of human postural sways is useful in examining postural stability. Postural sways is known to increase with age. There is limited information on postural sways measured using an accelerometer in healthy younger and older adults. The purpose of this study was to compare postural sways among healthy younger and older adults using an accelerometer in quiet standing. This is a pilot cross-sectional study involving 36 participants, 19 younger adults aged between 18 to 40 years old and 17 older adults aged between 60 to 80 years old. A tri-axial accelerometer was placed at the level of third lumbar vertebrae (L3) to measure participants’ postural sways. The tests were performed under two conditions; quiet standing eyes open (EO) and eyes closed (EC) for 30 seconds for each test. There were no significant differences found in quiet standing postural sways under both test conditions in each group (p=0.45) and between the two groups (p=0.32). Postural stability should be assessed in more challenging conditions among older adults in order to yield data that is more meaningful.
Keywords: Accelerometer; balance; postural sway; eye open; eye closed
ABSTRAK
Penilaian huyung postur adalah berguna dalam usaha mengkaji keseimbangan tubuh. Huyung postur dilaporkan meningkat dengan usia. Maklumat mengenai huyung postur yang dinilai menggunakan accelerometer dalam kalangan dewasa muda dan warga emas yang sihat adalah terhad. Tujuan kajian ini adalah untuk membandingkan huyung postur dalam kalangan orang dewasa muda dan warga emas menggunakan accelerometer. Kajian ini merupakan satu kajian rintis keratan rentas yang melibatkan 36 peserta, 19 orang dewasa muda berusia antara 18 hingga 40 tahun dan 17 warga emas berusia antara 60 hingga 80 tahun. Accelerometer tiga paksi telah dilekatkan di bahagian belakang pada peringkat lumbar 3 (L3) untuk mengukur huyung postur para peserta. Ujian huyung postur berdiri statik selama 30 saat telah dijalankan dalam dua keadaan; mata terbuka (EO) dan mata tertutup (EC). Keputusan menunjukkan tiada perbezaan bacaan accelerometer didapati pada ujian huyung postur berdiri statik dalam kedua-dua keadaan pada setiap kumpulan (p=0.45) dan juga di antara dua kumpulan dewasa muda dan warga emas (p=0.32). Keseimbangan tubuh harus dinilai dalam keadaan yang lebih mencabar dalam kalangan warga emas bagi mendapatkan data yang lebih bermakna.
Kata kunci: Accelerometer; keseimbangan; huyung postur; mata terbuka; mata tertutup
INTRODUCTION
The measure of human postural sways is useful in examining postural stability. Clinically, postural stability is a common assessment used for functional mobility and falls risk measure (Singh et al. 2015). Postural sways are continuous body
oscillations that are present even during quiet standing (Janusz et al. 2016).
Aging is associated with an increase in postural sways usually notable under the conditions of altered visual or somatosensory cues (Liaw et al
impaired reflexes, reduced muscle strength and decreased protective mechanism efficacy in older adults (Shaffer & Harrison 2007).
Various methods are available in measuring postural stability either subjectively or objectively.
There are no consensus on the best method to measure postural stability. However, there is a recommendation of outcome measures such as BESTest that could be used to measure comprehensive and identify the specific components of postural stability for training (Sibley et al. 2015).
Mostly, the simple outcome measures to assess postural stability used at clinical settings are subjective, for example the Romberg’s test, Berg Balance Scale (BBS) and Tinetti Balance Assessment. The advantages of using these outcome measures are that it is quick and does not require expensive equipment to perform the tests (Nnodim
& Yung 2015). It is noteworthy that these outcome measures to assess postural stability were designed and tested among people with impairments. Thus, using these outcome measures to assess postural stability can have a ceiling effect when used among people without any impairments. There is also a higher chance to score people without any impairments as not having any problems when using these outcome measures (Howe et al. 2011).
Objective assessment tools to measure postural stability are important to provide micro changes that may not be detected subjectively (Browne & O'Hare 2001), especially in high functioning community-dwelling older adults who may have near normal balance ability. However, these older adults may still have issues during
physical activity in the field of health sciences (Craig et al. 2003). It is also useful in evaluating and measuring the acceleration of postural sways objectively (Culhane et al. 2005; Garatachea et al.
2010). Information regarding measurements of postural sways among adults in different age groups using an accelerometer is limited. Quantifying micro sways during quiet standing may be useful in early detection of balance impairments for early intervention strategies in older adults. The aim of this pilot study was to compare postural sways quantified using postural body accelerations between healthy community-dwelling older and younger adults in quiet standing.
MATERIALS AND METHODS Accelerometer
Postural sways or body acceleration were measured using a 2g triaxial accelerometer (Model 2460-005 Silicon Designs, Inc, Kirkland Washington) at a frequency of 100 Hz. The accelerometer was calibrated prior to each test session by using the technique described by Ferraris et al. (1995). The accelerometer was attached to the participant’s lower back at the level of third lumbar vertebrae (L3), using a belt (Figure 1). The accelerometer was connected to a battery-operated data logger that was connected to a laptop. The accelerometer has previously been tested for accuracy and precision and for test-retest reliability during walking and standing with satisfying result (Godfrey et al. 2008).
Figure 1. Tri-axial Accelerometer Placement at third lumbar vertebrae (L3)
Participants
Two adult groups with a total of 36 participants participated in this study. Group one consisted of 17 community-dwelling older adults (3 males and 14 females) aged between 60 to 80 years, mean (SD) of 69.59 (5.52) years old. Group two had 19 younger adults aged 18 to 40 years old (8 males and 11 females), mean (SD) of 23.79 (3.05) year old. The demographic details of the participants are presented in Table 1. Participants were included if they were age between 18-40 years (for young adults) and 60-75 years (for elderly), able to stand unsupported, not known balance problem, neurology, or any premorbid conditions that may cause balance problems and was not on any medications that may affect their postural stability.
Written and verbal information was provided and informed consent was obtained. Ethical approval was obtained from the Secretariat for Research and Ethics of Universiti Kebangsaan Malaysia (UKM 1.5.3.4/244/NN-076-2012).
Test procedure
Palpation of participant's third of lumbar vertebra was performed by a final year physiotherapy undergraduate and marked using a non-permanent marker. An accelerometer mounted on a specially tailored belt was fixed on participant’s body using adhesive tape.
Participants were required to stand upright, shoulder width apart facing the wall looking ahead and focusing at a point (Point X) at the height of their eyes and remain in a comfortable position with hands along the side of the body without footwear.
Participants were required to stand still for 30 s for each of these conditions:
i) Stand upright on both feet with eyes opened (EO)
ii) Stand upright on both feet with eyes closed (EC)
Accelerometer data analysis
The acceleration data collected using the accelerometer was saved on a computer for further analysis. Of the 30 seconds standing tests, five seconds data at the beginning and end of each record was discarded in order to remove any noises as suggested in a previous study (O’Sullivan et al.
2009). This results in a 20 seconds of measuring time for each test condition. Root mean square (RMS) values for the axes were computed as the parameter for postural sways acceleration. The resultant acceleration vector (Ar) are the combinations of the acceleration measured in medio-lateral (ax), anterior-posterior (az) and vertical (ay) planes. The resultant acceleration (Ar) is calculated using the equation below;
Ar =
Deriving from the equation above, the root mean square (RMS) values for 20 seconds of each test condition is;
RMS =
The differences in the RMS values were used as an indicator in distinguishing the balance ability in quiet standing tests between tasks and age group.
Statistical Analysis
Statistical Package for the Social Sciences (SPSS®) version 19 (IBM Corporation, Armonk, NY, USA) was used to analyze the data. Shapiro-Wilk test showed that the data were normally distributed. A
Male 3(17.6) 8(42.1)
Female 14(82.4) 11(57.9)
Race
Malay 9(52.9) 12(63.2)
Indian 1(5.9) -
Chinese 7(41.2) 4(21.1)
Others - 3(15.8)
Table 2. Comparison for EO and EC test conditions in older and younger adults Test
Conditions
RMS
Mean (±SD)
Older Younger F p-value
EO 1.05 (±0.0046) 1.06 (±0.0038)
(1,16) =0.60 0.45
EC 1.05 (±0.0054) 1.05 (±0.0031)
*The test is statistically significant at p<0.05
Table 3. Comparison for EO and EC test conditions between the older and younger adults Adult
Group
RMS Mean (±SD)
EO EC F p-value
Older 1.05 (±0.0046) 1.05 (±0.0054)
(1,16) = 1.07 0.32 Younger 1.06(±0.0038) 1.05 (±0.0031)
*The test is statistically significant at p<0.05 EO and EC test conditions in older and younger
adults
Table 2 represents the comparison of the RMS values between the two groups and for two tests conditions. In older group, the value of the RMS parameter was increased slightly by 0.0002g in EC compared to EO. On the contrary, in the younger adult group, the RMS value of EO was increased slightly by 0.0003g from EC. However, there were no significant difference (F(1,16)= 601, p=0.45), in quiet standing postural sways under the conditions of EO and EC in both groups.
EO and EC test conditions between the older and younger adults
A slight increment in the RMS parameter values in the EC and EO between both groups was observed as shown in Table 3. The EO RMS values in the younger group was 0.0034g greater than older group. Similar to the values of EC, there was an increase by 0.0029g in older adult group. However, there was no significant difference demonstrated (F(1,16) = 1.071 with p= 0.32).
DISCUSSION
We aimed to compare postural sways quantified using postural body accelerations between healthy older and younger adults in quiet standing. The results showed no significant differences in the RMS values of postural sways between and within the groups during quiet standing in both eyes open and closed conditions. These results indicate that there were no differences in quiet standing postural sways in both test conditions in each group and between the two groups.
Similar results for quiet standing tests performed in both eyes open and closed conditions among older and younger adults measured using a force platform were reported (Kalisch et al. 2011).
The difference in this past study was that participants were required to raise both arms to 90o in standing. Although higher center of pressure (COP) scatter were found in older compared to younger adults, the difference were not significant (p>0.05).
In the study by Liaw and colleagues (2009) it was reported that older adults had greater postural imbalance and used hip strategy to achieve balance when measured using computerized dynamic posturography (CDP), during dynamic standing.
However, this was not the case in quiet standing as in our present study results. Our study results are also consistent with the findings by O’Sullivan and colleagues (2009) for quiet standing tests during eyes open and eyes closed, measured using a triaxial accelerometer. There was no significant difference shown (p= 0.46) although the RMS values for EC was slightly increased by 0.001g compared to EO among groups of older adults with and without a history of fall.
In our study, the tests were performed in quiet standing on firm surface where the participants were required to stand on the floor with conditions of;
eyes open and eyes closed for 30 seconds. One of the possible reasons for no difference in postural sways demonstrated between older and younger adults may be due to the methodology. It can be argued that postural stability was not challenged in both younger and older adults during quiet standing on a firm surface. Also, older adults in this study were community-dwelling and had no history of a fall. Thus, it can be speculated that older adults in our present study had good postural stability. There is also a possibility that 30 seconds of postural
stability measurements are not sufficient to detect any difference among healthy older adults.
Distinguishing tasks was possible when measuring using an accelerometer but it is noteworthy that these tasks were more complex (Mayogoitia et al. 2002). An acceleorometer was used to evaluate the COP displacements in quiet standing among healthy young males under the condition of EO and EC but with different width of base of support (BOS; feet placed closely together and apart). A significant (p<0.05) difference was found for the tasks requiring narrowed BOS. The authors reported that an accelerometer was more sensitive compared to the force platform, as it was able to distinguish more standing test conditions compared to when using a force platform.
As in the previous studies, it was shown that there is higher sensitivity of monitoring postural sways parameters under the circumstances of altered posture (Kalisch et al. 2011), altered supporting surface (Liaw et al. 2009; Nejc et al.
2010; O’Sullivan et al. 2009), narrowed BOS (Mayogoitia et al. 2002), absence of visual acuity (Kalisch et al. 2011; Mayogoitia et al. 2002;
O’Sullivan et al. 2009) and swayed visual together with swayed support (Liaw et al. 2009). Mancini &
Horak (2010) also reported that more significant results of balance assessment can be obtained if it was being evaluated during dynamic rather than static conditions as performed in our present study.
Our pilot study is limited to a small sample size from two age groups of healthy adults. Sample size calculations showed that 34 participants were required from each group for this study. More studies with a larger sample size are required to examine the differences in postural stability among healthy adults between different age groups performed under more challenging conditions when using an accelerometer. For instance, alteration of the supporting surface and body posture, the addition of swayed visual surround and the extension of the duration of the test.
CONCLUSION
The use of an accelerometer is advantageous as it is portable and allows assessment of postural stability.
However, measurements of postural sways using an accelerometer in healthy adults may require more challenging tests conditions to distinguish differences.
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NOR NAJWATUL AKMAL AB RAHMAN DEVINDER KAUR AJIT SINGH
SITI ZAFIRA BINTI ZAINAL ABIDIN
Physiotherapy Programme & Centre for Healthy Ageing and Wellness, Faculty of Health Sciences, Universiti Kebangsaan Malaysia,
Jalan Raja Muda Abdul Aziz, 50300, Kuala Lumpur, Malaysia.
NOR NAJWATUL AKMAL AB RAHMAN Faculty of Allied Health Sciences,
Cyberjaya University College of Medical Sciences, Cyberjaya, Selangor, Malaysia
NOR HANIZA BINTI ABDUL WAHAT SHAZARINA OTHMAN
Audiology Programme & Centre for Rehabilitation and Special Needs, Faculty of Health Sciences, Universiti Kebangsaan Malaysia,
Jalan Raja Muda Abdul Aziz, 50300, Kuala Lumpur, Malaysia
SHAZARINA OTHMAN
Oticon (M) Sdn Bhd, No 4, Jalan Rasah, 70300 Seremban, Negeri Sembilan, Malaysia DEEPASHINI HARITHASAN
Physiotherapy Programme & Centre for Rehabilitation and Special Needs, Faculty of Health Sciences, Universiti Kebangsaan Malaysia,
Jalan Raja Muda Abdul Aziz, 50300, Kuala Lumpur, Malaysia.
*Corresponding author: [email protected]