title: Adaptation and prosthesis effects on stride-to-stride fluctuations in amputee gait.
abstract: Twenty-four individuals with transtibial amputation were recruited to a randomized, crossover design study to examine stride-to-stride fluctuations of lower limb joint flexion/extension time series using the largest Lyapunov exponent (λ). Each individual wore a "more appropriate" and a "less appropriate" prosthesis design based on the subject's previous functional classification for a three week adaptation period. Results showed decreased λ for the sound ankle compared to the prosthetic ankle (F1,23 = 13.897, p = 0.001) and a decreased λ for the "more appropriate" prosthesis (F1,23 = 4.849, p = 0.038). There was also a significant effect for the time point in the adaptation period (F2,46 = 3.164, p = 0.050). Through the adaptation period, a freezing and subsequent freeing of dynamic degrees of freedom was seen as the λ at the ankle decreased at the midpoint of the adaptation period compared to the initial prosthesis fitting (p = 0.032), but then increased at the end compared to the midpoint (p = 0.042). No differences were seen between the initial fitting and the end of the adaptation for λ (p = 0.577). It is concluded that the λ may be a feasible clinical tool for measuring prosthesis functionality and adaptation to a new prosthesis is a process through which the motor control develops mastery of redundant degrees of freedom present in the system.
authors: Biomechanics Research Building, University of Nebraska at Omaha, Omaha, Nebraska, United States of America; Advanced Prosthetics Center, Omaha, Nebraska, United States of America.
authors: Shane R
authors: SR
authors: Wurdeman
authors: Biomechanics Research Building, University of Nebraska at Omaha, Omaha, Nebraska, United States of America.
authors: Sara A
authors: SA
authors: Myers
authors: Veterans Affairs Medical Center, Omaha, Nebraska, United States of America.
authors: Adam L
authors: AL
authors: Jacobsen
authors: Biomechanics Research Building, University of Nebraska at Omaha, Omaha, Nebraska, United States of America.
authors: Nicholas
authors: N
authors: Stergiou
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000368:Aged; D000674:Amputees; D001186:Artificial Limbs; D018592:Cross-Over Studies; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D013997:Time Factors