Submitted on June 12, 2008
Revised on January 28, 2009
Accepted on February 18, 2009
Fractal dynamics of human gait : a reassessment of Hausdorff et al. (1996)'s data
Didier Delignieres1* and Kjerstin Torre2
1 University Montpellier, Montpellier, France
2 Univesrity Montpellier I
* To whom correspondence should be addressed. E-mail: didier.delignieres{at}univ-montp1.fr.
We propose in this paper a reassessment of the original data of Hausdorff et al. (J. Appl. Physiol 80: 1448-1457, 1996). We confirm, using ARFIMA/ARMA 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 anti-persistent correlations, and 1/f fluctuations were evidenced in the asynchronies to the metronome. We show that the Super Central Pattern Generator model (SCPG, West B, Scarfetta N, Phys Rev E 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 supra-spinal 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.
