title: Dynamic stability of running: the effects of speed and leg amputations on the maximal Lyapunov exponent.
abstract: In this paper, we study dynamic stability during running, focusing on the effects of speed, and the use of a leg prosthesis. We compute and compare the maximal Lyapunov exponents of kinematic time-series data from subjects with and without unilateral transtibial amputations running at a wide range of speeds. We find that the dynamics of the affected leg with the running-specific prosthesis are less stable than the dynamics of the unaffected leg and also less stable than the biological legs of the non-amputee runners. Surprisingly, we find that the center-of-mass dynamics of runners with two intact biological legs are slightly less stable than those of runners with amputations. Our results suggest that while leg asymmetries may be associated with instability, runners may compensate for this effect by increased control of their center-of-mass dynamics.
authors.affiliation: Department of Applied Mathematics, University of Colorado Boulder, Boulder, Colorado 80309, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Look
authors.affiliation: Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado 80309, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Arellano
authors.affiliation: Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado 80309, USA.
authors.forename: Alena M
authors.initials: AM
authors.lastname: Grabowski
authors.affiliation: The Orthopedic Specialty Hospital, Murray, Utah 84107, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: McDermott
authors.affiliation: Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado 80309, USA.
authors.forename: Rodger
authors.initials: R
authors.lastname: Kram
authors.affiliation: Department of Computer Science, University of Colorado Boulder, Boulder, Colorado 80309, USA and Santa Fe Institute, Santa Fe, New Mexico 87501, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Bradley