title: Linear and Nonlinear Gait Features in Older Adults Walking on Inclined Surfaces at Different Speeds.
abstract: This study evaluated linear and nonlinear gait features in healthy older adults walking on inclined surfaces at different speeds. Thirty-seven active older adults (experimental group) and fifty young adults (control group) walked on a treadmill at 100% and ±20% of their preferred walking speed for 4 min under horizontal (0%), upward (UP) (+8%), and downward (DOWN) (-8%) conditions. Linear gait variability was assessed using the average standard deviation of trunk acceleration between strides (VAR). Gait stability was assessed using the margin of stability (MoS). Nonlinear gait features were assessed by using the maximum Lyapunov exponent, as a measure of local dynamic stability (LDS), and sample entropy (SEn), as a measure of regularity. VAR increased for all conditions, but the interaction effects between treadmill inclination and age, and speed and age were higher for young adults. DOWN conditions showed the lowest stability in the medial-lateral MoS, but not in LDS. LDS was smaller in UP conditions. However, there were no effects of age for either MoS or LDS. The values of SEn decreased almost linearly from the DOWN to the UP conditions, with significant interaction effects of age for anterior-posterior SEn. The overall results supported the hypothesis that inclined surfaces modulate nonlinear gait features and alter linear gait variability, particularly in UP conditions, but there were no significant effects of age for active older adults.
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Avenida Esperança s/n, Campus Samambaia, Goiânia, Goiás, 74690-900, Brazil. marcus@ufg.br.|Posgraduate Program in Electrical and Biomedical Engineering, Center for Innovation and Technology Assessment in Health, Universidade Federal de Uberlândia, Uberlândia, Brazil. marcus@ufg.br.
authors.forename: Marcus Fraga
authors.initials: MF
authors.lastname: Vieira
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Avenida Esperança s/n, Campus Samambaia, Goiânia, Goiás, 74690-900, Brazil.
authors.forename: Fábio Barbosa
authors.initials: FB
authors.lastname: Rodrigues
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Avenida Esperança s/n, Campus Samambaia, Goiânia, Goiás, 74690-900, Brazil.
authors.forename: Gustavo Souto
authors.initials: GS
authors.lastname: de Sá E Souza
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Avenida Esperança s/n, Campus Samambaia, Goiânia, Goiás, 74690-900, Brazil.
authors.forename: Rina Márcia
authors.initials: RM
authors.lastname: Magnani
authors.affiliation: Bioengineering and Biomechanics Laboratory, Universidade Federal de Goiás, Avenida Esperança s/n, Campus Samambaia, Goiânia, Goiás, 74690-900, Brazil.
authors.forename: Georgia Cristina
authors.initials: GC
authors.lastname: Lehnen
authors.affiliation: Posgraduate Program in Electrical and Biomedical Engineering, Center for Innovation and Technology Assessment in Health, Universidade Federal de Uberlândia, Uberlândia, Brazil.
authors.forename: Adriano O
authors.initials: AO
authors.lastname: Andrade
mesh_terms: D000054:Acceleration; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult
keywords: Inclined walking; Linear gait variability; Margin of stability; Maximum Lyapunov exponent; Nonlinear analysis; Sample entropy