Fractal dynamics of human gait: a reassessment of the 1996 data of Hausdorff et al.
We propose in this paper a reassessment of the original data of Hausdorff et al. (Hausdorff JM, Purdon PL, Peng C-K, Ladin Z, Wei JY, Goldberger AR. J Appl Physiol 80: 1448-1457, 1996). We confirm, using autoregressive fractionally integrated moving average modeling, the presence of genuine fractal correlations in stride interval series in self-paced conditions. In contrast with the conclusions of the authors, we show that correlations did not disappear in metronomic conditions. The series of stride intervals presented antipersistent correlations, and 1/f fluctuations were evidenced in the asynchronies to the metronome. We show that the super central pattern generator model (West B, Scafetta N. Phys Rev E Stat Nonlin Soft Matter Phys 67: 051917, 2003) allows accounting for the experimentally observed correlations in both self-paced and metronomic conditions, by the simple setting of the coupling strength parameter. We conclude that 1/f fluctuations in gait are not overridden by supraspinal influences when walking is paced by a metronome. The source of 1/f noise is still at work in this condition, but expressed differently under the influence of a continuous coupling process.
Delignières
Didier
D
EA 2991 Motor Efficiency and Deficiency, University Montpellier I, Montpellier, France. didier.delignieres@univ-montp1.fr
Torre
Kjerstin
K
D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D000465:Algorithms; D003627:Data Interpretation, Statistical; D005260:Female; D017709:Fractals; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D015233:Models, Statistical; D016138:Walking / Q000502:physiology; D055815:Young Adult