Nonlinear dynamics, psychology, and life sciences, 2010
Individuals with Parkinson's disease and the aged have a high prevalence of falls. Since an i... more Individuals with Parkinson's disease and the aged have a high prevalence of falls. Since an increase in the number of falls is associated with physical and psychological harm, it is prudent that biomechanical metrics be established that will accurately assess an individual's walking balance. In this investigation, we initially used a simple bipedal walking computer model to theoretically establish the relationship between attractor divergence and walking balance. The Lyapunov exponent was used to quantify the amount of divergence present in the walking attractor. Simulations from our model indicated that attractors that have a greater amount of divergence are more susceptible to falls from external perturbations. Based on the results of our simulations, we conducted an initial experiment to explore if the young, aged and individuals with Parkinson's disease have different degrees of attractor divergence. Our results indicate that individuals with Parkinson's disease ...
The Journal of sports medicine and physical fitness, 2003
It has been suggested that during running proper coordination between subtalar pronation/supinati... more It has been suggested that during running proper coordination between subtalar pronation/supination and knee flexion/extension via tibial rotation is important to attenuate ground reaction impact forces (GRIF). Lack of coordination over time may produce a wide range of injuries. It was hypothesized that increasing stride length would result in higher GRIF. It was also hypothesized that alterations in stride length would result in changes of the subtalar/knee coordination. Six subjects ran under 3 different stride lengths (normal stride, understride and overstride) at their self-selected pace. Sagittal, rear view kinematic data and GRIF kinetic data were collected. The subtalar/knee coordination was evaluated via timing and relative velocity measures. Repeated measures ANOVA were performed on these measures with a Tukey post-hoc analysis conducted where appropriate (p<0.01). Increased stride length produced significant increases in GRIF and significantly augmented the differences ...
This study investigated intralimb coordination during walking in young and elderly women using th... more This study investigated intralimb coordination during walking in young and elderly women using the theoretical model of dynamical systems. 20 women, 10 Young ( M age = 24.6 yr., SD = 3.2 yr.) and 10 Elderly ( M age = 73.7 yr., SD = 4.9 yr.), were videotaped during free speed gait and gait perturbed by an ankle weight. Two parameters, one describing the phasing relationship between segments (mean absolute relative phase) and the other the variability of this relationship (deviation in phase), were calculated from the kinematics. Two-way analysis of variance (age and weight) with repeated measures on weight indicated that during the braking period the weight increased the mean absolute relative phase between the shank and the thigh and decreased it between the foot and the shank. The Elderly women had significant smaller values for the mean absolute relative phase between the shank and the thigh during the braking period. For the same period, deviation in phase increased for the segme...
This investigation quantitatively characterized the certainty of the aging neuromuscular system i... more This investigation quantitatively characterized the certainty of the aging neuromuscular system in selecting a joint range of motion during gait based on the statistical concept of entropy. Elderly and young control groups walked on a treadmill at a self-selected pace. Joint angles were calculated for the ankle, knee and hip. We hypothesized that the aging group would exhibit less certainty in selecting a joint range of motion during gait. Our results supported this hypothesis, and indicated that aged individuals demonstrated statistically less certainty for the knee (16.8%) and hip (24.6%). We suggest that neurophysiological changes associated with aging may result in less certainty of the neuromuscular system in selecting a stable gait.
Journal of NeuroEngineering and Rehabilitation, 2008
Background Aging leads to increases in gait variability which may explain the large incidence of ... more Background Aging leads to increases in gait variability which may explain the large incidence of falls in the elderly. Body weight support training may be utilized to improve gait in the elderly and minimize falls. However, before initiating rehabilitation protocols, baseline studies are needed to identify the effect of body weight support on elderly gait variability. Our purpose was to determine the kinematic variability of the lower extremities in young and elderly healthy females at changing levels of body weight support during walking. Methods Ten young and ten elderly females walked on a treadmill for two minutes with a body weight support (BWS) system under four different conditions: 1 g, 0.9 g, 0.8 g, and 0.7 g. Three-dimensional kinematics was captured at 60 Hz with a Peak Performance high speed video system. Magnitude and structure of variability of the sagittal plane angular kinematics of the right lower extremity was analyzed using both linear (magnitude; standard deviati...
Chaos is a central feature of human locomotion and has been suggested to be a window to the contr... more Chaos is a central feature of human locomotion and has been suggested to be a window to the control mechanisms of locomotion. In this investigation, we explored how the principles of chaos can be used to control locomotion with a passive dynamic bipedal walking model that has a chaotic gait pattern. Our control scheme was based on the scientific evidence that slight perturbations to the unstable manifolds of points in a chaotic system will promote the transition to new stable behaviors embedded in the rich chaotic attractor. Here we demonstrate that hip joint actuations during the swing phase can provide such perturbations for the control of bifurcations and chaos in a locomotive pattern. Our simulations indicated that systematic alterations of the hip joint actuations resulted in rapid transitions to any stable locomotive pattern available in the chaotic locomotive attractor. Based on these insights, we further explored the benefits of having a chaotic gait with a biologically inspired artificial neural network (ANN) that employed this chaotic control scheme. Remarkably, the ANN was quite robust and capable of selecting a hip joint actuation that rapidly transitioned the passive dynamic bipedal model to a stable gait embedded in the chaotic attractor. Additionally, the ANN was capable of using hip joint actuations to accommodate unstable environments and to overcome unforeseen perturbations. Our simulations provide insight on the advantage of having a chaotic locomotive system and provide evidence as to how chaos can be used as an advantageous control scheme for the nervous system.
Parkinson's disease (PD) is a progressive debilitating neurodegenerative disorder clinically ... more Parkinson's disease (PD) is a progressive debilitating neurodegenerative disorder clinically manifest by motor, posture and gait abnormalities. Human neurophysiological studies recording local field potentials within the subthalamic nucleus and scalp-based electroencephalography have shown pathological beta synchrony throughout the basal ganglia-thalamic-cortical motor network in PD. Notably, suppression of this pathological beta synchrony by dopamine replacement therapy or deep-brain stimulation has been associated with improved motor function. However, due to the invasive nature of these studies, it remains unknown whether this "pathological beta" is actually stronger than that observed in healthy demographically matched controls. We used magnetoencephalography to investigate neuronal synchrony and oscillatory amplitude in the beta range and lower frequencies during the resting state in patients with PD and a matched group of patients without neurological disease. Pa...
Nonlinear dynamics, psychology, and life sciences, 2010
Individuals with Parkinson's disease and the aged have a high prevalence of falls. Since an i... more Individuals with Parkinson's disease and the aged have a high prevalence of falls. Since an increase in the number of falls is associated with physical and psychological harm, it is prudent that biomechanical metrics be established that will accurately assess an individual's walking balance. In this investigation, we initially used a simple bipedal walking computer model to theoretically establish the relationship between attractor divergence and walking balance. The Lyapunov exponent was used to quantify the amount of divergence present in the walking attractor. Simulations from our model indicated that attractors that have a greater amount of divergence are more susceptible to falls from external perturbations. Based on the results of our simulations, we conducted an initial experiment to explore if the young, aged and individuals with Parkinson's disease have different degrees of attractor divergence. Our results indicate that individuals with Parkinson's disease ...
The Journal of sports medicine and physical fitness, 2003
It has been suggested that during running proper coordination between subtalar pronation/supinati... more It has been suggested that during running proper coordination between subtalar pronation/supination and knee flexion/extension via tibial rotation is important to attenuate ground reaction impact forces (GRIF). Lack of coordination over time may produce a wide range of injuries. It was hypothesized that increasing stride length would result in higher GRIF. It was also hypothesized that alterations in stride length would result in changes of the subtalar/knee coordination. Six subjects ran under 3 different stride lengths (normal stride, understride and overstride) at their self-selected pace. Sagittal, rear view kinematic data and GRIF kinetic data were collected. The subtalar/knee coordination was evaluated via timing and relative velocity measures. Repeated measures ANOVA were performed on these measures with a Tukey post-hoc analysis conducted where appropriate (p<0.01). Increased stride length produced significant increases in GRIF and significantly augmented the differences ...
This study investigated intralimb coordination during walking in young and elderly women using th... more This study investigated intralimb coordination during walking in young and elderly women using the theoretical model of dynamical systems. 20 women, 10 Young ( M age = 24.6 yr., SD = 3.2 yr.) and 10 Elderly ( M age = 73.7 yr., SD = 4.9 yr.), were videotaped during free speed gait and gait perturbed by an ankle weight. Two parameters, one describing the phasing relationship between segments (mean absolute relative phase) and the other the variability of this relationship (deviation in phase), were calculated from the kinematics. Two-way analysis of variance (age and weight) with repeated measures on weight indicated that during the braking period the weight increased the mean absolute relative phase between the shank and the thigh and decreased it between the foot and the shank. The Elderly women had significant smaller values for the mean absolute relative phase between the shank and the thigh during the braking period. For the same period, deviation in phase increased for the segme...
This investigation quantitatively characterized the certainty of the aging neuromuscular system i... more This investigation quantitatively characterized the certainty of the aging neuromuscular system in selecting a joint range of motion during gait based on the statistical concept of entropy. Elderly and young control groups walked on a treadmill at a self-selected pace. Joint angles were calculated for the ankle, knee and hip. We hypothesized that the aging group would exhibit less certainty in selecting a joint range of motion during gait. Our results supported this hypothesis, and indicated that aged individuals demonstrated statistically less certainty for the knee (16.8%) and hip (24.6%). We suggest that neurophysiological changes associated with aging may result in less certainty of the neuromuscular system in selecting a stable gait.
Journal of NeuroEngineering and Rehabilitation, 2008
Background Aging leads to increases in gait variability which may explain the large incidence of ... more Background Aging leads to increases in gait variability which may explain the large incidence of falls in the elderly. Body weight support training may be utilized to improve gait in the elderly and minimize falls. However, before initiating rehabilitation protocols, baseline studies are needed to identify the effect of body weight support on elderly gait variability. Our purpose was to determine the kinematic variability of the lower extremities in young and elderly healthy females at changing levels of body weight support during walking. Methods Ten young and ten elderly females walked on a treadmill for two minutes with a body weight support (BWS) system under four different conditions: 1 g, 0.9 g, 0.8 g, and 0.7 g. Three-dimensional kinematics was captured at 60 Hz with a Peak Performance high speed video system. Magnitude and structure of variability of the sagittal plane angular kinematics of the right lower extremity was analyzed using both linear (magnitude; standard deviati...
Chaos is a central feature of human locomotion and has been suggested to be a window to the contr... more Chaos is a central feature of human locomotion and has been suggested to be a window to the control mechanisms of locomotion. In this investigation, we explored how the principles of chaos can be used to control locomotion with a passive dynamic bipedal walking model that has a chaotic gait pattern. Our control scheme was based on the scientific evidence that slight perturbations to the unstable manifolds of points in a chaotic system will promote the transition to new stable behaviors embedded in the rich chaotic attractor. Here we demonstrate that hip joint actuations during the swing phase can provide such perturbations for the control of bifurcations and chaos in a locomotive pattern. Our simulations indicated that systematic alterations of the hip joint actuations resulted in rapid transitions to any stable locomotive pattern available in the chaotic locomotive attractor. Based on these insights, we further explored the benefits of having a chaotic gait with a biologically inspired artificial neural network (ANN) that employed this chaotic control scheme. Remarkably, the ANN was quite robust and capable of selecting a hip joint actuation that rapidly transitioned the passive dynamic bipedal model to a stable gait embedded in the chaotic attractor. Additionally, the ANN was capable of using hip joint actuations to accommodate unstable environments and to overcome unforeseen perturbations. Our simulations provide insight on the advantage of having a chaotic locomotive system and provide evidence as to how chaos can be used as an advantageous control scheme for the nervous system.
Parkinson's disease (PD) is a progressive debilitating neurodegenerative disorder clinically ... more Parkinson's disease (PD) is a progressive debilitating neurodegenerative disorder clinically manifest by motor, posture and gait abnormalities. Human neurophysiological studies recording local field potentials within the subthalamic nucleus and scalp-based electroencephalography have shown pathological beta synchrony throughout the basal ganglia-thalamic-cortical motor network in PD. Notably, suppression of this pathological beta synchrony by dopamine replacement therapy or deep-brain stimulation has been associated with improved motor function. However, due to the invasive nature of these studies, it remains unknown whether this "pathological beta" is actually stronger than that observed in healthy demographically matched controls. We used magnetoencephalography to investigate neuronal synchrony and oscillatory amplitude in the beta range and lower frequencies during the resting state in patients with PD and a matched group of patients without neurological disease. Pa...
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