Mu Qiao1, Jody A Feld2, Jason R Franz3. 1. Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, United States. 2. Human Movement Science Curriculum, University of North Carolina at Chapel Hill, United States. 3. Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, United States. Electronic address: jrfranz@email.unc.edu.
Abstract
BACKGROUND: Older adults are more susceptible to balance perturbations during walking than young adults. However, we lack an individual joint-level understanding of how aging affects the neuromechanical strategies used to accommodate balance perturbations. RESEARCH QUESTION: We investigated gait phase-dependence in and aging effects on leg joint kinematic variability during walking with balance perturbations. We hypothesized that leg joint variability would: 1) vary across the gait cycle and 2) increase with balance perturbations. We also hypothesized that perturbation effects on leg joint kinematic variability would be larger and more pervasive in older versus young adults. METHODS: We collected leg joint kinematics in young and older adults walking with and without mediolateral optical flow perturbations of different amplitudes. RESULTS: We first found that leg joint variability during walking is gait phase-dependent, with step-to-step adjustments occurring predominantly during push-off and early swing. Second, young adults accommodated perturbations almost exclusively by increasing coronal plane hip joint variability, likely to adjust step width. Third, perturbations elicited larger and more pervasive increases in all joint kinematic outcome measures in older adults. Finally, we also provide insight into which joints contribute more to foot placement variability in walking, adding that variability in sagittal plane knee and coronal plane hip joint angles contributed most to that in step length and step width, respectively. SIGNIFICANCE: Taken together, our findings may be highly relevant to identifying specific joint-level therapeutic targets to mitigate balance impairment in our aging population.
BACKGROUND: Older adults are more susceptible to balance perturbations during walking than young adults. However, we lack an individual joint-level understanding of how aging affects the neuromechanical strategies used to accommodate balance perturbations. RESEARCH QUESTION: We investigated gait phase-dependence in and aging effects on leg joint kinematic variability during walking with balance perturbations. We hypothesized that leg joint variability would: 1) vary across the gait cycle and 2) increase with balance perturbations. We also hypothesized that perturbation effects on leg joint kinematic variability would be larger and more pervasive in older versus young adults. METHODS: We collected leg joint kinematics in young and older adults walking with and without mediolateral optical flow perturbations of different amplitudes. RESULTS: We first found that leg joint variability during walking is gait phase-dependent, with step-to-step adjustments occurring predominantly during push-off and early swing. Second, young adults accommodated perturbations almost exclusively by increasing coronal plane hip joint variability, likely to adjust step width. Third, perturbations elicited larger and more pervasive increases in all joint kinematic outcome measures in older adults. Finally, we also provide insight into which joints contribute more to foot placement variability in walking, adding that variability in sagittal plane knee and coronal plane hip joint angles contributed most to that in step length and step width, respectively. SIGNIFICANCE: Taken together, our findings may be highly relevant to identifying specific joint-level therapeutic targets to mitigate balance impairment in our aging population.