title: Coordination dynamics of (a)symmetrically loaded gait.
abstract: Asymmetries in the resonant frequency of limbs/effectors lead to changes in coordination dynamics, including deviations in relative phase at ϕ = 0 or π rad and reduced stability. These effects have been successfully modeled by the extended Haken-Kelso-Bunz (HKB) coupled oscillator model (Kelso et al. in Attention and performance XIII. Erlbaum, Hillsdale, pp 139-169, 1990), and supported in laboratory tasks of rhythmic limb motions. Efforts to apply the HKB model to walking have supported the predicted deviations in phase, but not the expected decreases in coordination stability. The lack of stability effects arising from asymmetries may be due to the stabilizing influence of a treadmill or may be obscured by the balance requirements and ground impacts in gait. This study examined these possibilities by investigating walking overground with ankle weights of 3 or 6 kg to create asymmetries between the legs, as well as symmetrical loads. Participants walked without a metronome and separately with a metronome to control speed and cadence. Coordination dynamics between the legs were quantified through mean and standard deviation (SD) of ϕ, while individual leg local dynamic stability was calculated as maximum Lyapunov exponent (λ (MAX)). Irrespective of the condition, asymmetrical loads led to deviations in phase from antiphase with the loaded leg lagging behind the other, and both SDϕ and λ (MAX) increased (i.e., stability decreased). Symmetrical loads had no effect on phase deviations, but decreased stability. Overall, these findings indicate that the HKB model captures coordination dynamics in walking, but also highlights limitations in modeling the influence of loads on an individual limb.
authors.affiliation: School of Physical Therapy and Athletic Training, College of Health Sciences, Old Dominion University, 3118 Health Sciences Building, Norfolk, VA, 23529, USA. dmrussel@odu.edu.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Russell
authors.affiliation: Johns Hopkins School of Medicine, Center for Autism and Related Disorders, Kennedy Krieger Institute, 3901 Greenspring Avenue, Baltimore, MD, 21211, USA. haworth@kennedykrieger.org.
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Haworth
authors.affiliation: Division of Science, The Pennsylvania State University - Berks, Reading, PA, 19610, USA. cxm58@psu.edu.
authors.forename: Cesar
authors.initials: C
authors.lastname: Martinez-Garza
mesh_terms: D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D016138:Walking / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
keywords: Locomotion; Resonant frequency; Stability; Variability