title: Short-term step-to-step correlation in plantar pressure distributions during treadmill walking, and implications for footprint trail analysis.
abstract: The gait cycle is continuous, but for practical reasons one is often forced to analyze one or only a few adjacent cycles, for example in non-treadmill laboratory investigations and in fossilized footprint analysis. The nature of variability in long-term gait cycle dynamics has been well-investigated, but short-term variability, and specifically correlation, which are highly relevant to short gait bouts, have not. We presently tested for step-to-step autocorrelation in a total of 5243 plantar pressure (PP) distributions from ten subjects who walked at 1.1m/s on an instrumented treadmill. Following spatial foot alignment, data were analyzed both from three points of interest (POI): heel, central metatarsals, and hallux, and for the foot surface as a whole, in a mass-univariate manner. POI results revealed low average step-to-step autocorrelation coefficients (r=0.327±0.094; mean±st. dev.). Formal statistical testing of the whole-foot r distributions reached significance over an average of only 0.42±0.52% of the foot's surface, even for a highly conservative uncorrected threshold of p<0.05. The common assumption, that short gait bouts consist of independent cycles, is therefore not refuted by the present PP results.
authors.affiliation: Department of Bioengineering, Shinshu University, Tokida 3-15-1 Ueda, Nagano 386-8567, Japan. Electronic address: tpataky@shinshu-u.ac.jp.
authors.forename: Todd C
authors.initials: TC
authors.lastname: Pataky
authors.forename: Russell
authors.initials: R
authors.lastname: Savage
authors.forename: Karl T
authors.initials: KT
authors.lastname: Bates
authors.forename: William I
authors.initials: WI
authors.lastname: Sellers
authors.forename: Robin H
authors.initials: RH
authors.lastname: Crompton
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005528:Foot / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006365:Heel / Q000502:physiology; D006801:Humans; D008297:Male; D008684:Metatarsus / Q000502:physiology; D011312:Pressure; D055815:Young Adult
keywords: Autocorrelation; Foot biomechanics; Gait dynamics; Pedobarography; Statistical parametric mapping