Comparison of Trunk Activity during Gait Initiation and Walking in Humans

To understand the role of trunk muscles in maintenance of dynamic postural equilibrium we investigate trunk movements during gait initiation and walking, performing trunk kinematics analysis, Erector spinae muscle (ES) recordings and dynamic analysis. ES muscle expressed a metachronal descending pattern of activity during walking and gait initiation. In the frontal and horizontal planes, lateroflexion and rotation occur before in the upper trunk and after in the lower trunk. Comparison of ES muscle EMGs and trunk kinematics showed that trunk muscle activity precedes corresponding kinematics activity, indicating that the ES drive trunk movement during locomotion and thereby allowing a better pelvis mobilization. EMG data showed that ES activity anticipates propulsive phases in walking with a repetitive pattern, suggesting a programmed control by a central pattern generator. Our findings also suggest that the programs for gait initiation and walking overlap with the latter beginning before the first has ended

Asymmetry measures for quantification of mechanisms contributing to dynamic stability during stepping-in-place gait

The goal of this study is to introduce and to motivate the use of new quantitative methods to improve our understanding of mechanisms that contribute to the control of dynamic balance during gait. Dynamic balance refers to the ability to maintain a continuous, oscillating center-of-mass (CoM) motion of the body during gait even though the CoM frequently moves outside of the base of support. We focus on dynamic balance control in the frontal plane or medial–lateral (ML) direction because it is known that active, neurally-mediated control mechanisms are necessary to maintain ML stability. Mechanisms that regulate foot placement on each step and that generate corrective ankle torque during the stance phase of gait are both known to contribute to the generation of corrective actions that contribute to ML stability. Less appreciated is the potential role played by adjustments in step timing when the duration of the stance and/or swing phases of gait can be shortened or lengthened to allow torque due to gravity to act on the body CoM over a shorter or longer time to generate corrective actions. We introduce and define four asymmetry measures that provide normalized indications of the contribution of these different mechanisms to gait stability. These measures are ‘step width asymmetry’, ‘ankle torque asymmetry’, ‘stance duration asymmetry’, and ‘swing duration asymmetry’. Asymmetry values are calculated by comparing corresponding biomechanical or temporal gait parameters from adjacent steps. A time of occurrence is assigned to each asymmetry value. An indication that a mechanism is contributing to ML control is obtained by comparing asymmetry values to the ML body motion (CoM angular position and velocity) at the time points associated with the asymmetry measures. Example results are demonstrated with measures obtained during a stepping-in-place (SiP) gait performed on a stance surface that either remained fixed and level or was pseudorandomly tilted to disturb balance in the ML direction. We also demonstrate that the variability of asymmetry measures obtained from 40 individuals during unperturbed, self-paced SiP were highly correlated with corresponding coefficient of variation measures that have previously been shown to be associated with poor balance and fall risk

Age Related Changes in Balance and Gait

abstract: Gait and balance disorders are the second leading cause of falls in the elderly. Investigating the changes in static and dynamic balance due to aging may provide a better understanding of the effects of aging on postural control system. Static and dynamic balance were evaluated in a total of 21 young (21-35 years) and 22 elderly (50-75 years) healthy subjects while they performed three different tasks: quiet standing, dynamic weight shifts, and over ground walking. During the quiet standing task, the subjects stood with their eyes open and eyes closed. When performing dynamic weight shifts task, subjects shifted their Center of Pressure (CoP) from the center target to outward targets and vice versa while following real-time feedback of their CoP. For over ground walking tasks, subjects performed Timed Up and Go test, tandem walking, and regular walking at their self-selected speed. Various quantitative balance and gait measures were obtained to evaluate the above respective balance and walking tasks. Total excursion, sway area, and mean frequency of CoP during quiet standing were found to be the most reliable and showed significant increase with age and absence of visual input. During dynamic shifts, elderly subjects exhibited higher initiation time, initiation path length, movement time, movement path length, and inaccuracy indicating deterioration in performance. Furthermore, the elderly walked with a shorter stride length, increased stride variability, with a greater turn and turn-to-sit duration. Significant correlations were also observed between measures derived from the different balance and gait tasks. Thus, it can be concluded that aging deteriorates the postural control system affecting static and dynamic balance and some of the alterations in CoP and gait measures may be considered as protective mechanisms to prevent loss of balance.Dissertation/ThesisM.S. Bioengineering 201

Biomechanics of assisted locomotion in elderly osteoarthritis patients

Osteoarthritis is the most widespread musculoskeletal disease worldwide among the elderly. It causes joint pain that can affect locomotion and reduce mobility. For osteoarthritis patients, maintaining walking ability is considered the most beneficial way to preserve their quality of life. Walking sticks are widely used by elderly adults and have been shown to have a supportive role on locomotion. In this thesis I carried out four experiments: The first study investigated how footwear affects the locomotion of elderly patients suffering from this disease. In the second chapter the gait of elderly walking stick users was analysed in conjunction with their responses to a questionnaire with a view to understanding the causes and context of walking stick use in their everyday environments. My findings demonstrated that the majority of participants experienced greater pain after prolonged use of their walking stick. In the last two experiments I investigated how the use of a walking stick combined with aspects of the individual’s locomotor environment (e.g. indoor and outdoor, level and sloped surfaces) to influence gait. Overall, osteoarthritis, advanced age and challenging locomotor environments can influence their quality of life and the risk of falling

Biomechanics of assisted locomotion in elderly osteoarthritis patients

Osteoarthritis is the most widespread musculoskeletal disease worldwide among the elderly. It causes joint pain that can affect locomotion and reduce mobility. For osteoarthritis patients, maintaining walking ability is considered the most beneficial way to preserve their quality of life. Walking sticks are widely used by elderly adults and have been shown to have a supportive role on locomotion. In this thesis I carried out four experiments: The first study investigated how footwear affects the locomotion of elderly patients suffering from this disease. In the second chapter the gait of elderly walking stick users was analysed in conjunction with their responses to a questionnaire with a view to understanding the causes and context of walking stick use in their everyday environments. My findings demonstrated that the majority of participants experienced greater pain after prolonged use of their walking stick. In the last two experiments I investigated how the use of a walking stick combined with aspects of the individual’s locomotor environment (e.g. indoor and outdoor, level and sloped surfaces) to influence gait. Overall, osteoarthritis, advanced age and challenging locomotor environments can influence their quality of life and the risk of falling

Postural Sway and Sway-adaptation During Exposure to Optic Flow: the Effect of Stimulus Periodicity and Concurrent Cognitive Tasks

Stable upright stance is achieved through an active postural control process that requires the accurate integration of sensory feedback signals from the visual, graviceptive and proprioceptive systems. Previous studies have shown that this integration process may involve "reweighting", whereby the relative contributions of the various sensory signals are dynamically altered in order to minimize reliance on unreliable signals. In addition, evidence suggests that feedback control by itself cannot explain experimental observations of postural behavior. In light of these observations, the current study proposed that a predictive mechanism exists within the postural control system that can identify the highly repetitive pattern within a predictable sensory input, and can use this information to facilitate the sensory reweighting process. The objectives of the current work were to: (1) uncover experimental evidence of such a predictive mechanism, through examination of postural sway responses in healthy young adults exposed to various types of predictable and unpredictable moving visual scenes; (2) examine how this predictive mechanism manifested itself in individuals who were particularly reliant on visual sensory information; and (3) determine if this predictive mechanism was influenced by cognitive tasks, which are thought to interact with the sensory reweighting process.Data revealed that in healthy young adults predictable stimuli elicited improved sway performance compared to unpredictable stimuli, as indicated by significant decreases in both overall sway magnitude, and the time required for sensory reweighting to occur. This effect was enhanced during the performance of a concurrent cognitive task, but was not observed in visually dependent individuals, apparently due to an inability to perform sensory reweighting. Taken together, these observations support the existence of a predictive component to postural control that can alter the dynamic reweighting of sensory inputs during exposure to predictable stimuli. These findings may have implications for the design of experiments involving moving visual scenes, as well as for the treatment of individuals suffering from certain balance disorders