1 Introduction
2 Methods
2.1 Subjects
Body characteristics | Young | Elderly |
---|---|---|
Age (years) | 21.4 ± 2.5 | 73.2 ± 6.5 |
Body mass (kg) | 63.7 ± 14.8 | 68.73 ± 13.6 |
Body height (cm) | 167.0 ± 6.3 | 163.6 ± 5.49 |
RQ total path length | 1.47 ± 0.24 | 1.44 ± 0.26 |
RQ sway area PCA | 1.50 ± 0.66 | 1.20 ± 0.45 |
2.2 Instrumentation
2.3 Procedure
2.4 Statistical methods
3 Results
3.1 Test–retest reliability of time-domain variables
3.1.1 Standing on a firm surface with eyes open
Age group | 1st measurement Average ± SD (SEM) | 2nd measurement Average ± SD (SEM) | ICC | 95 % CI | |
---|---|---|---|---|---|
Medio-lateral variability (cm) | Young | 0.44 ± 0.1 (0.02) | 0.47 ± 0.13 (0.03) | 0.56 | 0.04–0.80 |
Elderly | 0.57 ± 0.08 (0.02) | 0.56 ± 0.13 (0.03) | 0.80 | 0.41–0.93 | |
Antero-posterior variability (cm) | Young | 0.51 ± 0.16 (0.03) | 0.49 ± 0.18 (0.04) | 0.62 | 0.15–0.83 |
Elderly | 0.62 ± 0.19 (0.05) | 0.61 ± 0.21 (0.06) | 0.87 | 0.63–0.96 | |
Medio-lateral path length (cm) | Young | 51. 88 ± 8.78 (1.72) | 48.76 ± 10.22 (2.00) | 0.68 | 0.31–0.86 |
Elderly | 80. 16 ± 17.55 (4.53) | 75.93 ± 21.69 (5.60) | 0.91 | 0.73–0.97 | |
Antero-posterior path length (cm) | Young | 46.54 ± 9.28 (1.82) | 43.83 ± 10.48 (2.06) | 0.65 | 0.24–0.84 |
Elderly | 61.14 ± 15.67 (4.05) | 60.52 ± 15.24 (3.94) | 0.85 | 0.56–0.95 | |
Total path length (cm) | Young | 77.52 ± 12.85 (2.52) | 72.93 ± 15.03 (2.95) | 0.69 | 0.32–0.86 |
Elderly | 111.60 ± 21.33 (5.51) | 107.85 ± 26.43 (6.82) | 0.91 | 0.73–0.97 | |
Mean velocity (cm/s) | Young | 1.29 ± 0.21 (0.04) | 1.22 ± 0.25 (0.05) | 0.69 | 0.32–0.86 |
Elderly | 1.86 ± 0.36 (0.09) | 1.80 ± 0.44 (0.11) | 0.91 | 0.73–0.97 | |
Sway area FAO (cm2) | Young | 3.56 ± 1.38 (0.28) | 3.67 ± 1.79 (0.35) | 0.74 | 0.42–0.89 |
Elderly | 6.32 ± 2.04 (0.53) | 6.50 ± 3.00 (0.78) | 0.88 | 0.65–0.96 | |
Sway area PCA (cm2) | Young | 2.61 ± 1.19 (0.23) | 2.81 ± 1.61 (0.32) | 0.77 | 0.49–0.90 |
Elderly | 4.11 ± 1.45 (0.38) | 4.09 ± 1.71 (0.44) | 0.85 | 0.56–0.95 | |
Fractal dimension ML short interval | Young | 1.10 ± 0.02 (0.00) | 1.10 ± 0.02 (0.00) | 0.67 | 0.27–0.85 |
Elderly | 1.09 ± 0.02 (0.01) | 1.09 ± 0.02 (0.01) | 0.90 | 0.70–0.97 | |
Fractal dimension ML long interval | Young | 1.81 ± 0.13 (0.02) | 1.77 ± 0.13 (0.03) | 0.57 | 0.05–0.81 |
Elderly | 1.85 ± 0.11 (0.03) | 1.88 ± 0.10 (0.03) | 0.56 | −0.31–0.85 | |
Fractal dimension AP short interval | Young | 1.18 ± 0.04 (0.01) | 1.17 ± 0.04 (0.01) | 0.85 | 0.66–0.93 |
Elderly | 1.13 ± 0.03 (0.01) | 1.11 ± 0.03 (0.01) | 0.88 | 0.64–0.96 | |
Fractal dimension AP long interval | Young | 1.67 ± 0.14 (0.03) | 1.68 ± 0.16 (0.03) | 0.34 | −0.48–0.70 |
Elderly | 1.76 ± 0.14 (0.04) | 1.77 ± 0.15 (0.04) | 0.77 | 0.30–0.92 |
3.1.2 Standing on a firm surface with eyes closed
Age group | 1st measurement Average ± SD (SEM) | 2nd measurement Average ± SD (SEM) | ICC | 95 % CI | |
---|---|---|---|---|---|
Medio-lateral variability (cm) | Young | 0.53 ± 0.14 (0.03) | 0.55 ± 0.14 (0.03) | 0.40 | −0.35–0.73 |
Elderly | 0.62 ± 0.14 (0.04) | 0.64 ± 0.11 (0.03) | 0.89 | 0.68–0.96 | |
Antero-posterior variability (cm) | Young | 0.56 ± 0.25 (0.05) | 0.51 ± 0.16 (0.03) | 0.82 | 0.60–0.92 |
Elderly | 0.62 ± 0.16 (0.04) | 0.66 ± 0.19 (0.05) | 0.65 | −0.04–0.88 | |
Medio-lateral path length (cm) | Young | 77.21 ± 21.14 (4.23) | 70.86 ± 17.20 (3.44) | 0.77 | 0.48–0.90 |
Elderly | 114.99 ± 29.89 (7.72) | 115.32 ± 26.36 (6.81) | 0.93 | 0.78–0.98 | |
Antero-posterior path length (cm) | Young | 69.80 ± 20.18 (4.04) | 64.25 ± 15.38 (3.08) | 0.85 | 0.67–0.94 |
Elderly | 87.78 ± 27.42 (7.08) | 86.71 ± 18.89 (4.88) | 0.85 | 0.55–0.95 | |
Total path length (cm) | Young | 115.68 ± 30.87 (6.17) | 106.35 ± 24.12 (4.82) | 0.83 | 0.61–0.93 |
Elderly | 160.35 ± 39.56 (10.22) | 159.78 ± 31.89 (8.23) | 0.89 | 0.68–0.96 | |
Mean velocity (cm/s) | Young | 1.93 ± 0.52 (0.10) | 1.77 ± 0.40 (0.08) | 0.83 | 0.61–0.93 |
Elderly | 2.67 ± 0.66 (0.17) | 2.66 ± 0.53 (0.14) | 0.89 | 0.68–0.96 | |
Sway area FAO (cm2) | Young | 5.64 ± 3.26 (0.65) | 5.43 ± 2.64 (0.53) | 0.85 | 0.66–0.93 |
Elderly | 8.28 ± 3.31 (0.85) | 9.40 ± 3.30 (0.85) | 0.61 | −0.17–0.87 | |
Sway area PCA (cm2) | Young | 3.68 ± 2.52 (0.50) | 3.46 ± 1,92 (0.38) | 0.84 | 0.65–0.93 |
Elderly | 4.72 ± 2.12 (0.55) | 5.19 ± 2.02 (0.52) | 0.71 | 0.13–0.90 | |
Fractal dimension ML short interval | Young | 1.10 ± 0.02 (0.00) | 1.10 ± 0.02 (0.00) | 0.80 | 0.56–0.91 |
Elderly | 1.11 ± 0.03 (0.01) | 1.11 ± 0.01 (0.00) | 0.58 | −0.27–0.86 | |
Fractal dimension ML long interval | Young | 1.93 ± 0.11 (0.02) | 1.87 ± 0.08 (0.02) | 0.47 | −0.19–0.76 |
Elderly | 1.95 ± 0.05 (0.01) | 1.97 ± 0.04 (0.01) | 0.65 | −0.04–0.88 | |
Fractal dimension AP short interval | Young | 1.15 ± 0.04 (0.01) | 1.14 ± 0.03 (0.01) | 0.74 | 0.43–0.89 |
Elderly | 1.14 ± 0.04 (0.01) | 1.13 ± 0.04 (0.01) | 0.97 | 0.92–0.99 | |
Fractal dimension AP long interval | Young | 1.88 ± 0.09 (0.02) | 1.87 ± 0.08 (0.02) | 0.39 | −0.36–0.73 |
Elderly | 1.87 ± 0.11 (0.03) | 1.90 ± 0.10 (0.03) | 0.59 | −0.21–0.86 |
3.1.3 Standing on a compliant surface with eyes open
Age group | 1st measurement Average ± SD (SEM) | 2nd measurement Average ± SD (SEM) | ICC | 95 % CI | |
---|---|---|---|---|---|
Medio-lateral variability (cm) | Young | 0.65 ± 0.12 (0.02) | 0.65 ± 0.09 (0.02) | 0.83 | 0.62–0.92 |
Elderly | 0.92 ± 0.16 (0.04) | 0.89 ± 0.23 (0.06) | 0.83 | 0.50–0.94 | |
Antero-posterior variability (cm) | Young | 0.78 ± 0.21 (0.04) | 0.81 ± 0.17 (0.03) | 0.66 | 0.23–0.85 |
Elderly | 0.97 ± 0.22 (0.06) | 1.00 ± 0.25 (0.06) | 0.72 | 0.17–0.91 | |
Medio-lateral path length (cm) | Young | 96.87 ± 17.97 (3.6) | 88.89 ± 16.47 (3.29) | 0.77 | 0.40–0.90 |
Elderly | 167 ± 34.61 (8.94) | 153.70 ± 40.97 (10.58) | 0.90 | 0.69–0.97 | |
Antero-posterior path length (cm) | Young | 87.09 ± 15.36 (3.07) | 78.82 ± 13.32 (2.66) | 0.70 | 0.20–0.88 |
Elderly | 142.12 ± 29.25 (7.55) | 131.73 ± 37.63 (9.72) | 0.90 | 0.70–0.97 | |
Total path length (cm) | Young | 144.63 ± 24.49 (4.9) | 131.74 ± 21.44 (4.29) | 0.74 | 0.24–0.90 |
Elderly | 243.57 ± 46.15 (11.92) | 224.85 ± 62.46 (16.13) | 0.92 | 0.77–0.98 | |
Mean velocity (cm/s) | Young | 2.41 ± 0.41 (0.08) | 2.20 ± 0.36 (0.07) | 0.74 | 0.24–0.90 |
Elderly | 4.06 ± 0.77 (0.20) | 3.75 ± 1.04 (0.27) | 0.92 | 0.77–0.98 | |
Sway area FAO (cm2) | Young | 9.51 ± 3.6 (0.74) | 8.95 ± 2.39 (0.49) | 0.67 | 0.25–0.85 |
Elderly | 19.04 ± 6.64 (1.71) | 17.69 ± 7.32 (1.89) | 0.89 | 0.67–0.96 | |
Sway area PCA (cm2) | Young | 6.24 ± 2.66 (0.53) | 6.26 ± 1.96 (0.39) | 0.73 | 0.38–0.88 |
Elderly | 10.76 ± 3.78 (0.98) | 10.75 ± 4.74 (1.22) | 0.84 | 0.53–0.95 | |
Fractal dimension ML short interval | Young | 1.10 ± 0.02 (0.00) | 1.10 ± 0.02 (0.00) | 0.79 | 0.52–0.90 |
Elderly | 1.11 ± 0.02 (0.01) | 1.12 ± 0.02 (0.01) | 0.80 | 0.40–0.93 | |
Fractal dimension ML long interval | Young | 1.90 ± 0.08 (0.02) | 1.90 ± 0.09 (0.02) | 0.75 | 0.45–0.89 |
Elderly | 1.93 ± 0.04 (0.01) | 1.93 ± 0.08 (0.02) | 0.73 | 0.20–0.91 | |
Fractal dimension AP short interval | Young | 1.12 ± 0.03 (0.01) | 1.12 ± 0.03 (0.00) | 0.80 | 0.55–0.91 |
Elderly | 1.12 ± 0.02 (0.00) | 1.11 ± 0.01 (0.00) | 0.13 | −1.59–0.71 | |
Fractal dimension AP long interval | Young | 1.77 ± 0.13 (0.03) | 1.70 ± 0.16 (0.03) | 0.46 | −0.21–0.76 |
Elderly | 1.86 ± 0.11 (0.03) | 1.78 ± 0.11 (0.03) | 0.82 | 0.45–0.94 |
3.1.4 Standing on a compliant surface with eyes closed
Age group | 1st measurement Average ± SD (SEM) | 2nd measurement Average ± SD (SEM) | ICC | 95 % CI | |
---|---|---|---|---|---|
Medio-lateral variability (cm) | Young | 1.18 ± 0.18 (0.04) | 1.16 ± 0.20 (0.04) | 0.76 | 0.46–0.89 |
Elderly | 1.51 ± 0.20 (0.06) | 1.46 ± 0.29 (0.08) | 0.80 | 0.33–0.94 | |
Antero-posterior variability (cm) | Young | 1.33 ± 0.17 (0.03) | 1.21 ± 0.20 (0.04) | 0.67 | 0.14–0.87 |
Elderly | 1.54 ± 0.24 (0.07) | 1.49 ± 0.19 (0.05) | 0.63 | −0.21–0.89 | |
Medio-lateral path length (cm) | Young | 222.93 ± 56.79 (11.36) | 213.27 ± 55.57 (11.12) | 0.90 | 0.77–0.95 |
Elderly | 328.61 ± 78.34 (21.73) | 314.43 ± 78.10 (21.66) | 0.88 | 0.60–0.96 | |
Antero-posterior path length (cm) | Young | 231.83 ± 52.32 (10.46) | 213.51 ± 59.36 (11.87) | 0.88 | 0.69–0.95 |
Elderly | 287.80 ± 61.11 (16.95) | 292.80 ± 58.35 (16.18) | 0.87 | 0.59–0.96 | |
Total path length (cm) | Young | 357.76 ± 82.37 (16.47) | 335.63 ± 87.52 (17.50) | 0.90 | 0.76–0.96 |
Elderly | 485.07 ± 102.25 (28.36) | 476.47 ± 104.15 (28.89) | 0.90 | 0.68–0.97 | |
Mean velocity (cm/s) | Young | 5.97 ± 1.37 (0.28) | 5.60 ± 1.46 (0.29) | 0.90 | 0.76–0.96 |
Elderly | 8.09 ± 1.71 (0.47) | 7.95 ± 1.74 (0.48) | 0.90 | 0.68–0.97 | |
Sway area FAO (cm2) | Young | 31.45 ± 7.64 (1.53) | 30.18 ± 9.92 (1.98) | 0.83 | 0.62–0.92 |
Elderly | 51.86 ± 15.08 (4.18) | 49.71 ± 14.61 (4.05) | 0.69 | −0.02–0.91 | |
Sway area PCA (cm2) | Young | 19.14 ± 4.85 (0.97) | 17.17 ± 5.17 (1.03) | 0.83 | 0.57–0.93 |
Elderly | 28.03 ± 6.77 (1.88) | 26.32 ± 7.03 (1.95) | 0.87 | 0.57–0.96 | |
Fractal dimension ML short interval | Young | 1.11 ± 0.02 (0.00) | 1.11 ± 0.02 (0.00) | 0.78 | 0.50–0.90 |
Elderly | 1.12 ± 0.03 (0.01) | 1.11 ± 0.02 (0.01) | 0.93 | 0.77–0.98 | |
Fractal dimension ML long interval | Young | 1.98 ± 0.04 (0.01) | 1.97 ± 0.04 (0.01) | 0.68 | 0.29–0.86 |
Elderly | 1.99 ± 0.03 (0.01) | 1.99 ± 0.02 (0.01) | 0.16 | −1.77–0.74 | |
Fractal dimension AP short interval | Young | 1.15 ± 0.05 (0.01) | 1.14 ± 0.04 (0.01) | 0.86 | 0.70–0.94 |
Elderly | 1.14 ± 0.03 (0.01) | 1.13 ± 0.03 (0.01) | 0.85 | 0.49–0.95 | |
Fractal dimension AP long interval | Young | 1.98 ± 0.04 (0.01) | 1.98 ± 0.04 (0.01) | 0.65 | 0.22–0.84 |
Elderly | 1.97 ± 0.04 (0.01) | 1.99 ± 0.03 (0.01) | 0.33 | −1.19–0.80 |