Kinematic variability, fractal dynamics and local dynamic stability of treadmill walking

Table 1 Comparison between Overground and Treadmill Walking

		Overground Walking		Treadmill Walking		Effect Size		T-test	T²-test
N = 20		Mean ± SD	Confidence interval	Mean ± SD	Confidence interval	Abs.	Norm.	p	p
	ML	0.08 ± 0.03	0.07 - 0.09	0.07 ± 0.03	0.06 - 0.09	0.00	-0.12	0.59
Mean variability (SD, g)	V	0.08 ± 0.03	0.07 - 0.09	0.08 ± 0.03	0.06 - 0.09	-0.01	-0.16	0.48	0.87
	AP	0.08 ± 0.03	0.07 - 0.09	0.08 ± 0.03	0.07 - 0.09	0.00	-0.01	0.96
Stride time (mean, s)		1.06 ± 0.06	1.04 - 1.09	1.10 ± 0.07	1.07 - 1.13	0.03	0.53	0.01
Stride time variability (CV, %)		2.74 ± 0.87	2.36 - 3.12	3.03 ± 1.44	2.40 - 3.66	0.29	0.24	0.43
Scaling exponent α (DFA)		0.81 ± 0.09	0.78 - 0.85	0.72 ± 0.13	0.67 - 0.78	-0.09	-0.80	0.01
	ML	0.75 ± 0.11	0.70 - 0.79	0.68 ± 0.15	0.61 - 0.74	-0.07	-0.53	0.01
Short term stability (λ*_S)	V	0.75 ± 0.14	0.69 - 0.82	0.68 ± 0.16	0.61 - 0.75	-0.07	-0.48	0.01
	AP	0.72 ± 0.10	0.68 - 0.76	0.66 ± 0.13	0.60 - 0.71	-0.06	-0.57	0.02	0.00
	ML	0.022 ± 0.007	0.019 - 0.025	0.018 ± 0.008	0.015 - 0.021	-0.004	-0.60	0.02
Long term stability (λ*_L)	V	0.048 ± 0.014	0.042 - 0.054	0.040 ± 0.015	0.034 - 0.046	-0.008	-0.54	0.00
	AP	0.041 ± 0.008	0.038 - 0.044	0.039 ± 0.013	0.033 - 0.045	-0.002	-0.15	0.48

The Descriptive statistics of variability indexes are expressed as mean, Standard Deviation (SD) and 95% Confidence Interval (mean ± 1.96 times the Standard Error of the Mean). The effect size is given as Absolute (Abs.) and Normalized (Norm.) values, i.e. respectively the difference between Overground (OW) and Treadmill (TW) conditions (Abs.) and the difference normalized by SD (Hedge's g). The t-test column shows the p values of paired t-tests between TW and OW conditions. T²-test is the Hotelling multivariate test by regrouping MeanSD and λ*. Significant results (p < 0.05) are printed in bold. ML, V and AP stand for respectively Medio-Lateral, Vertical and Antero-posterior, i.e. the 3 directions of the triaxial accelerometer.

ISSN: 1743-0003