J Clin Med Res

Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc

Journal website https://www.jocmr.org

Short Communication

Volume 16, Number 4, April 2024, pages 174-181

Feasibility Study of a Prototype Wearable Inertial Measurement Unit for Elderly Postural Sway Assessment

Figure 1. A prototype of the inertial sensor system. (a) Sensor placement in relation to the center of mass (COM) at the L5 vertebra in the lumbar region. (b, c) Subcomponents of the inertial measurement unit (IMU). (d) An assembled IMU.

Figure 2. Static standing balance test under four conditions: standing stance with arms at sides (a), semi-tandem stance (b), tandem stance (front of non-dominant foot placed beside heel of dominant foot) (c), and one-leg standing (d).

Figure 3. Summation of distance (SD), the sway diagram obtained from the IMU under each testing condition: (a) standing stance with arms at sides, (b) semi-tandem stance, (c) tandem stance and (d) one-leg standing. IMU: inertial measurement unit.

Figure 4. Boxplot depicting the median (50th percentile) and maximum and minimum values for each IMU parameter of the static standing balance test under the four conditions among both the non-risk and potential-risk groups (a) RMS. (b) Range. (c) SD. (d) SA. ST: standing stance with arms at sides; S-TD: semi-tandem stance; TD: tandem stance; OLS: one-leg standing; RMS: root mean square of magnitude; Range: summation of the range of signals; SA: summation of the sway area; SD: summation of distance; IMU: inertial measurement unit.

**Table 1.** Demographic Data and Balance Test of the Elderly Participants
Description	Potential risk (n = 68)	Non-risk (n = 35)	P value
*Significant difference at P < 0.05. BMI: body mass index; SPPB: Short Physical Performance Battery; Thai-FRT: fall risk assessment test, Thai version; Min: minimum; Max: maximum.
Age (year)	68.5 (5.64)	60/87	68.4 (5.80)	60/84	0.66
Weight (kg)	56.41 (11.25)	29/85	54.14 (10.12)	30/72	0.32
Height (cm)	155.76 (7.71)	137/175	156.03 (7.74)	138/170	0.87
BMI (kg/m²)	23.24 (4.29)	33.20/12.23	22.25 (4.07)	13.33/30.22	0.32
Gait speed (m/s)	0.81 (0.14)	0.34/0.99	1.13 (0.11)	1/1.51	< 0.001*
SPPB	10.84 (1.31)	6/12	11.91 (0.28)	11/12	< 0.001*
Thai-FRT	2.37 (1.65)	0/8	1.80 (1.08)	0/5	0.04*

Table 1. Demographic Data and Balance Test of the Elderly Participants

Description

Potential risk (n = 68)

Non-risk (n = 35)

P value

Mean (SD)

Min/Max

Mean (SD)

Min/ Max

*Significant difference at P < 0.05. BMI: body mass index; SPPB: Short Physical Performance Battery; Thai-FRT: fall risk assessment test, Thai version; Min: minimum; Max: maximum.

Age (year)

68.5 (5.64)

60/87

68.4 (5.80)

60/84

0.66

Weight (kg)

56.41 (11.25)

29/85

54.14 (10.12)

30/72

0.32

Height (cm)

155.76 (7.71)

137/175

156.03 (7.74)

138/170

0.87

BMI (kg/m²)

23.24 (4.29)

33.20/12.23

22.25 (4.07)

13.33/30.22

0.32

Gait speed (m/s)

0.81 (0.14)

0.34/0.99

1.13 (0.11)

1/1.51

< 0.001*

SPPB

10.84 (1.31)

6/12

11.91 (0.28)

11/12

< 0.001*

Thai-FRT

2.37 (1.65)

0/8

1.80 (1.08)

0/5

0.04*

**Table 2.** Body Sway of IMU Variables for Each Test Condition
Variable	ST	S-TD	TD	OLS
^aCompared with ST, significant difference at P value < 0.001 (pairwise Mann-Whitney tests). ^bCompared with S-TD, significant difference at P value < 0.001 (pairwise Mann-Whitney tests). ^cCompared with TD, significant difference at P value < 0.001 (pairwise Mann-Whitney tests). IMU: inertial measurement unit; ST: standing stance with arms at sides; S-TD: semi-tandem stance; TD: tandem stance; OLS: one-leg standing; RMS: root mean square of magnitude; Range: summation of the range of signals; SA: summation of the sway area; SD: summation of distance.
RMS (degree/s)	1.436 ± 1.15	9.998/0.616	1.769 ± 1.10^a	6.315/0.733	2.630 ± 1.94^b	12.732/0.876	5.193 ± 5.53^c	39.025/1.509
Range (degree/s)	3.534 ± 3.84	28.973/1.060	4.619 ± 4.41^a	24.153/1.178	6.704 ± 5.93^b	38.338/1.609	13.256 ± 17.88^c	117.180/2.379
SA (degree)	10.756 ± 7.59	69.918/2.030	12.999 ± 6.96^a	47.220/2.113	19.334 ± 12.95^b	82.514/7.122	33.940 ± 25.06^c	168.009/3.290
SD (degree)	62.867 ± 47.69	470.535/30.824	82.572 ± 44.54^a	297.023/28.664	130.218 ± 88.56^b	573.348/42.351	216.006 ± 168.29^c	1,186.118/18.933

Table 2. Body Sway of IMU Variables for Each Test Condition

Variable

S-TD

OLS

Mean ± standard deviation

Max/Min

Mean ± standard deviation

Max/Min

Mean ± standard deviation

Max/Min

Mean ± standard deviation

Max/Min

^aCompared with ST, significant difference at P value < 0.001 (pairwise Mann-Whitney tests). ^bCompared with S-TD, significant difference at P value < 0.001 (pairwise Mann-Whitney tests). ^cCompared with TD, significant difference at P value < 0.001 (pairwise Mann-Whitney tests). IMU: inertial measurement unit; ST: standing stance with arms at sides; S-TD: semi-tandem stance; TD: tandem stance; OLS: one-leg standing; RMS: root mean square of magnitude; Range: summation of the range of signals; SA: summation of the sway area; SD: summation of distance.

RMS (degree/s)

1.436 ± 1.15

9.998/0.616

1.769 ± 1.10^a

6.315/0.733

2.630 ± 1.94^b

12.732/0.876

5.193 ± 5.53^c

39.025/1.509

Range (degree/s)

3.534 ± 3.84

28.973/1.060

4.619 ± 4.41^a

24.153/1.178

6.704 ± 5.93^b

38.338/1.609

13.256 ± 17.88^c

117.180/2.379

SA (degree)

10.756 ± 7.59

69.918/2.030

12.999 ± 6.96^a

47.220/2.113

19.334 ± 12.95^b

82.514/7.122

33.940 ± 25.06^c

168.009/3.290

SD (degree)

62.867 ± 47.69

470.535/30.824

82.572 ± 44.54^a

297.023/28.664

130.218 ± 88.56^b

573.348/42.351

216.006 ± 168.29^c

1,186.118/18.933

**Table 3.** IMU Body Sway Variables Between Non-Risk and Risk of Falling
Variable	SBS, mean (standard deviation)	STD, mean (standard deviation)	TD, mean (standard deviation)	OLS, mean (standard deviation)
*Significant difference at P value < 0.001, Mann-Whitney U tests. IMU: inertial measurement unit; ST: standing stance with arms at sides; S-TD: semi-tandem stance; TD: tandem stance; OLS: one-leg standing; RMS: root mean square of magnitude; Range: summation of the range of signals; SA: summation of the sway area; SD: summation of distance.
RMS (degree/s)	1.44 (1.15)			1.77 (1.10)			2.63 (1.94)			5.19 (5.53)
	1.53 (1.31)	1.25 (0.73)	0.19	1.94 (1.20)	1.44 (0.80)	0.01*	2.89 (2.23)	2.13 (1.03)	0.08	5.17 (4.30)	5.24 (7.43)	> 0.05
Range (degree/s)	3.53 (3.84)			4.62 (4.41)			6.70 (5.93)			13.26 (17.88)
	3.89 (4.41)	2.84 (2.26)	0.33	5.09 (4.64)	3.70 (3.82)	0.04*	7.45 (6.85)	5.26 (3.17)	0.11	13.39 (14.04)	12.99 (23.89)	0.03*
SA (degree)	10.76 (7.58)			13.00 (6.96)			19.33 (12.95)			33.94 (25.06)
	11.39 (8.79)	9.52 (4.25)	0.23	14.22 (7.75)	10.63 (4.26)	0.01*	21.01 (14.79)	16.08 (7.45)	0.07	34.53 (20.36)	32.79 (32.63)	0.04*
SD (degree)	62.87 (47.69)			82.57 (44.54)			130.22 (88.56)			216.01 (168.29)
	67.05 (1.20)	54.73 (18.02)	0.36	89.02 (50.93)	70.04 (24.38)	0.11	139.18 (101.86)	112.81 (51.11)	0.41	215.94 (128.23)	216.14 (229.27)	0.11

Table 3. IMU Body Sway Variables Between Non-Risk and Risk of Falling

Variable

SBS, mean (standard deviation)

STD, mean (standard deviation)

TD, mean (standard deviation)

OLS, mean (standard deviation)

Data

P value

Data

P value

Data

P value

Data

P value

Risk

Non-risk

Risk

Non-risk

Risk

Non risk

Risk

Non-risk

*Significant difference at P value < 0.001, Mann-Whitney U tests. IMU: inertial measurement unit; ST: standing stance with arms at sides; S-TD: semi-tandem stance; TD: tandem stance; OLS: one-leg standing; RMS: root mean square of magnitude; Range: summation of the range of signals; SA: summation of the sway area; SD: summation of distance.

RMS (degree/s)

1.44 (1.15)

1.77 (1.10)

2.63 (1.94)

5.19 (5.53)

1.53 (1.31)

1.25 (0.73)

0.19

1.94 (1.20)

1.44 (0.80)

0.01*

2.89 (2.23)

2.13 (1.03)

0.08

5.17 (4.30)

5.24 (7.43)

> 0.05

Range (degree/s)

3.53 (3.84)

4.62 (4.41)

6.70 (5.93)

13.26 (17.88)

3.89 (4.41)

2.84 (2.26)

0.33

5.09 (4.64)

3.70 (3.82)

0.04*

7.45 (6.85)

5.26 (3.17)

0.11

13.39 (14.04)

12.99 (23.89)

0.03*

SA (degree)

10.76 (7.58)

13.00 (6.96)

19.33 (12.95)

33.94 (25.06)

11.39 (8.79)

9.52 (4.25)

0.23

14.22 (7.75)

10.63 (4.26)

0.01*

21.01 (14.79)

16.08 (7.45)

0.07

34.53 (20.36)

32.79 (32.63)

0.04*

SD (degree)

62.87 (47.69)

82.57 (44.54)

130.22 (88.56)

216.01 (168.29)

67.05 (1.20)

54.73 (18.02)

0.36

89.02 (50.93)

70.04 (24.38)

0.11

139.18 (101.86)

112.81 (51.11)

0.41

215.94 (128.23)

216.14 (229.27)

0.11