Persistent fluctuations in stride intervals under fractal auditory stimulation

PLoS One. 2014 Mar 20;9(3):e91949. doi: 10.1371/journal.pone.0091949. eCollection 2014.

Abstract

Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acoustic Stimulation*
  • Adult
  • Algorithms
  • Female
  • Fractals*
  • Gait / physiology*
  • Humans
  • Male

Grants and funding

This work was supported by SKILLS, an Integrated Project (FP6-IST Contract #035005) of the Commission of the European Community. Andreas Daffertshofer received financial support from the Netherlands Organisation for Scientific Research (NWO grant #400-08-127). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.