Abstract
Previous research indicates the correlation structure of gait parameters (i.e., fractal dynamics) decreases with age. This decrease is suggested to reflect a reduced capacity for locomotor adaptation in older adults. The purpose of this study was to investigate potential differences between physical activity-matched young and older adults’ fractal dynamics and gait adaptability during unperturbed and asymmetric walking, and to determine if fractal dynamics predict adaptive capacity. Fifteen young (28.9 ± 5.6 years, nine women) and 15 older (64.7 ± 2.7, nine women) adults with similar habitual physical activity levels walked at preferred speed, half of preferred speed, and asymmetrically whereby their dominant and non-dominant legs moved at preferred and half-preferred speed, respectively. Fractal correlations (scaling exponent α) of stride times were assessed through detrended fluctuation analysis, and gait adaptation to asymmetric walking on the basis of lower limb relative phase. Both cohorts displayed similar fractal dynamics at preferred speed and asymmetric walking, while older adults exhibited greater α during slow walking. Both groups exhibited comparable gait adaptation to split-belt walking based on analysis of lower limb relative phase. Fractal dynamics during preferred speed and asymmetric walking was moderately associated with gait adaptation in the young and older adult cohorts, respectively. In these activity-matched groups, there were no age-based reductions in fractal dynamics or gait adaptation, and fractal scaling α was moderately associated with gait adaptation. These findings suggest that stride time fractal dynamics and gait adaptation may be preserved in older adults who habitually perform moderate intensity physical activity.
Highlights
In recent decades, the study of gait dynamics has evolved from quantifying the magnitude of gait parameter variability to evaluating the structure of this variability
Hypothesis 5 was partially supported in that α in the faster-moving leg was moderately associated with gait adaptation (PhaseDEV) in young adults, while this adaptation in the older adults was moderately related to α in the slower-moving leg. These results indicate that fractal dynamics and gait adaptability are largely preserved in older adults with PA levels comparable to those of young adults
The lack of difference in fractal dynamics between active young and older adults during unperturbed walking at preferred speed suggests that an active lifestyle may mitigate previously reported age-based changes in fractal dynamics
Summary
The study of gait dynamics has evolved from quantifying the magnitude of gait parameter variability to evaluating the structure of this variability. Split-belt treadmill walking, where one belt moves at a different speed than the other, reveals that participants consistently attempt to maintain or regain symmetry between legs, quantified as deviation from intended leg phasing (PhaseDEV, i.e., individuals attempt to walk with legs in antiphase, even when belts are moving at different speeds) or step length symmetry (Dietz et al, 1994; Choi and Bastian, 2007; Bruijn et al, 2012) Older adults adapt their gait patterns less and at a slower rate compared to young adults (Bruijn et al, 2012), as reflected by greater step length asymmetry during splitbelt walking, suggesting a lower capacity to adapt. In both the young and older groups, (5) stride time α would be associated with gait adaptation, whereby higher α (i.e., greater statistical persistence) would correlate with better gait adaptation (i.e., lower PhaseDEV)
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