Study of age-related changes in postural control during quiet standing through Linear Discriminant Analysis

Cavalheiro, Guilherme L; Almeida, Maria Fernanda S; Pereira, Adriano A; Andrade, Adriano O

doi:10.1186/1475-925X-8-35

BioMedical Engineering OnLine

Table 2 Analysis of the computed features from the displacement of the COP.

From: Study of age-related changes in postural control during quiet standing through Linear Discriminant Analysis

	Young Adult (Groups 1 and 2)		Elderly Adult (Groups 6 and 7)		ANOVA *p-value*		Correlation with age		Correlation Groups
Features	OE	CE	OE	CE	OE	CE	OE	CE
Mean Velocity	6.15	9.45	8.27	14.52	<		r = 0.3	r = 0.28
Ap (mm/s) *	± 1.32	± 3.08	± 3.69	± 10.74	0.03				A
Mean Velocity	5.40	7.54	7.14	12.91	<	<	r = 0.25	r = 0.29
Ml (mm/s) *	± 1.05	± 2.77	± 3.35	± 9.15	0.04	0.02			B
Mean Velocity	9.11	13.45	12.12	21.55	<	<	r = 0.29	r = 0.29
RD (mm/s) *	± 1.59	± 4.05	± 5.43	± 15.63	0.03	0.04			C
Range	21.10	27.84	18.62	27.90			r = -0.03	r = -0.07
Ap (mm)	± 5.57	± 8.03	± 4.74	± 10.80					D
Range	19.80	21.59	20.37	24.53			r = -0.05	r = 0.02
Ml (mm)	± 6.40	± 7.32	± 7.98	± 10.43					E
Displacement	230.6	320.0	299.3	500.2	<	<	r = 0.27	r = 0.28
Ap (mm) *	± 47.7	± 90.7	± 118.8	± 369.2	0.03	0.05			A
Displacement	171.4	235.8	229.4	414.7	<	<	r = 0.28	r = 0.3
Ml (mm) *	± 30.8	± 81.6	± 102.1	± 300.6	0.03	0.02			B
Displacement	273.4	403.6	363.7	646.7	<	<	r = 0.29	r = 0.29
RD (mm) *	± 47.6	± 121.4	± 163.0	± 469.2	0.03	0.04			C
RMS	4.52	5.74	3.60	4.91			r = 0.42	r = 0.48
Ap (mm)	± 1.52	± 1.82	± 0.94	± 1.95			p < 0.01	p < 0.001	F
RMS	4.04	4.27	3.79	4.57			r = 0.33	r = 0.44
Ml (mm)	± 1.39	± 1.47	± 1.22	± 1.82				p < 0.001	G
Mean Freq.	0.21	0.25	0.33	0.42	<	<	r = 0.41	r = 0.51
Ap (Hz) *	± 0.06	± 0.07	± 0.16	± 0.19	0.01	0.001	p < 0.01	p < 0.001	F, H
Mean Freq.	0.22	0.28	0.30	0.41	<	<	r = 0.34	r = 0.46
Ml (Hz) *	± 0.07	± 0.06	± 0.08	± 0.12	0.01	0.001	p < 0.01	p < 0.001	G, I
Peak Freq.	0.05	0.08	0.09	0.19			r = 0.27	r = 0.28
Ap (Hz)	± 0.03	± 0.06	± 0.07	± 0.24
Peak Freq.	0.06	0.10	0.07	0.15			r = 0.13	r = 0.25
Ml (Hz)	± 0.03	± 0.07	± 0.05	± 0.09
F50	0.083	0.13	0.20	0.27	<	<	r = 0.43	r = 0.48
Ap (Hz) *	± 0.03	± 0.05	± 0.14	± 0.18	0.01	0.01	p < 0.001	p < 0.001	H
F50	0.11	0.16	0.17	0.28	<	<	r = 0.28	r = 0.45
Ml (Hz) *	± 0.05	± 0.05	± 0.10	± 0.12	0.04	0.001		p < 0.001	I
F80	0.25	0.34	0.46	0.63	<	<	r = -0.29	r = -0.22
Ap (Hz) *	± 0.11	± 0.12	± 0.26	± 0.33	0.01	0.001			D
F80	0.30	0.36	0.40	0.59	<	<	r = -0.14	r = -0.05
Ml (Hz) *	± 0.11	± 0.08	± 0.14	± 0.23	0.03	0.001			E
Total Power	23.99	38.40	14.35	28.14			r = -0.28	r = -0.2
Ap	± 17.88	± 25.04	± 7.44	± 23.95					D
Total Power	19.20	21.44	16.44	24.57			r = -0.16	r = -0.05
Ml	± 12.80	± 14.53	± 10.54	± 19.45					E
Conf. Ellipse	223.0	325.5	172.6	305.3			r = -0.23	r = -0.14
area (mm²)	± 128.9	± 210.4	± 93.0	± 249.5					J
Conf. Ellipse	10.77	12.29	8.79	11.02			r = -0.31	r = -0.2
major axis (mm)	± 3.29	± 3.69	± 2.48	± 4.11					D, J
Conf. Ellipse	1.97	1.78	2.16	2.20		<	r = 0.09	r = 0.31
angle (rad)*	± 0.38	± 0.36	± 0.58	± 0.40		0.01
SDA - Ds	0.13	0.33	0.21	0.69			r = 0.21	r = 0.24
Ap	± 0.06	± 0.21	± 0.18	± 0.89					A
SDA - Ds	0.12	0.23	0.21	0.58	<	<	r = 0.26	r = 0.3
Ml *	± 0.04	± 0.16	± 0.17	± 0.57	0.04	0.01			B
SDA - Dl	0.05	0.05	0.02	0.02	<		r = -0.27	r = -0.23
Ap *	± 0.04	± 0.05	± 0.02	± 0.04	0.04
SDA - Dl	0.03	0.02	0.02	0.02			r = -0.16	r = -0.09
Ml	± 0.02	± 0.03	± 0.02	± 0.02
SDA - Hs	1.81	1.78	1.74	1.76	<		r = -0.31	r = -0.16
Ap *	± 0.06	± 0.04	± 0.08	± 0.06	0.01
SDA - Hs	1.80	1.77	1.77	1.78			r = -0.11	r = 0.03
Ml	± 0.05	± 0.05	± 0.05	± 0.06
SDA - Hl	0.64	0.44	0.32	0.23	<	<	r = -0.44	r = -0.44
Ap *	± 0.22	± 0.19	± 0.24	± 0.17	0.001	0.01	p < 0.001	p < 0.001
SDA - Hl	0.44	0.30	0.33	0.21			r = -0.23	r = -0.18
Ml	± 0.20	± 0.13	± 0.17	± 0.13
SDA-critical time	1.08	1.31	1.04	0.95		<	r = -0.1	r = -0.38
Ap (s) *	± 0.51	± 0.31	± 0.41	± 0.42		0.01		p < 0.01
SDA-critical time	1.43	1.28	1.25	0.98		<	r = -0.19	r = -0.38
Ml (s) *	± 0.78	± 0.33	± 0.32	± 0.27		0.01		p < 0.01
SDA (mm²)	0.16	0.41	0.17	0.43			r = -0.03	r = -0.02
critical mag.-Ap	± 0.14	± 0.27	± 0.09	± 0.31
SDA (mm²)	0.21	0.30	0.21	0.38			r = -0.08	r = 0.01
critical mag.-Ml	± 0.18	± 0.22	± 0.13	± 0.27
DFA - α	1.43	1.57	1.49	1.62			r = 0.16	r = 0.12
Ap	± 0.09	± 0.09	± 0.13	± 0.16
DFA - α	1.72	1.78	1.70	1.81			r = -0.09	r = 0.01
Ml	± 0.06	± 0.09	± 0.12	± 0.12
H _R/S	0.97	1.01	0.99	1.02			r = 0.2	r = 0.04
Ap	± 0.04	± 0.02	± 0.03	± 0.02
H _R/S	1.03	1.03	1.02	1.03			r = -0.09	r = -0.01
Ml	± 0.004	± 0.005	± 0.01	± 0.01
ApEn	0.008	0.008	0.010	0.012	<	<	r = 0.24	r = 0.43
Ap *	± 0.002	± 0.002	± 0.003	± 0.005	0.05	0.01		p < 0.001
ApEn	0.007	0.009	0.008	0.011		<	r = 0.14	r = 0.29
Ml *	± 0.002	± 0.002	± 0.002	± 0.003		0.01

Note that OE is the experimental condition of opened eyes whereas CE is the closed eyes. The mean and standard deviation are presented for each feature. Features that presented a significant difference between the groups are highlighted with '*' and in this case the estimated p-value of the ANOVA is shown. The correlation between the age and the feature is also presented. In the last column we present the analysis of the correlation between the studied features. When a correlation coefficient larger than 0.9 was found the features were included in the same group labeled by letters A, B, C, D, E, F, G, H, I, J.

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ISSN: 1475-925X

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