INTRODUCTION Several studies have attempted prediction of traumatic falls in the elderly, with mi... more INTRODUCTION Several studies have attempted prediction of traumatic falls in the elderly, with mixed results. One study included self-reports of imbalance, a history of falls, and measures of function in daily living, reporting prediction accuracy up to 79% [1]. Another model restricted selection of predictive variables to measures of static posture [2], neglecting dynamic measures of balance function during locomotion.
Gait patterns of the elderly are often adjusted to accommodate for reduced function in the balanc... more Gait patterns of the elderly are often adjusted to accommodate for reduced function in the balance control system. Recent work has demonstrated the effectiveness of artificial neural network (ANN) modeling in mapping gait measurements onto descriptions of whole body motion during locomotion. Accurate risk assessment is necessary for reducing incidence of falls. Further development of the balance estimation model has been used to test the feasibility of detecting balance impairment using tasks of sample categorization and falls risk estimation. Model design included an ANN and a statistical discrimination method. Sample categorization results reached accuracy of 0.89. Relative risk was frequently assessed at high or very high risk for experiencing falls in a sample of balance impaired older adults. The current model shows potential for detecting balance impairment and estimating falls risk, thereby indicating the need for referral for falls prevention intervention.
Zero-velocity assumption has been used for estimation of foot trajectory and stride length during... more Zero-velocity assumption has been used for estimation of foot trajectory and stride length during running from the data of foot-mounted inertial measurement units (IMUs). Although the assumption provides a reasonable initialization for foot trajectory and stride length estimation, the other source of errors related to the IMU’s orientation still remains. The purpose of this study was to develop an improved foot trajectory and stride length estimation method for the level ground running based on the displacement of the foot. Seventy-nine runners performed running trials at 5 different paces and their running motions were captured using a motion capture system. The accelerations and angular velocities of left and right feet were measured with two IMUs mounted on the dorsum of each foot. In this study, foot trajectory and stride length were estimated using zero-velocity assumption with IMU data, and the orientation of IMU was estimated to calculate the mediolateral and vertical distanc...
Introduction: Loading of a residual limb within a prosthetic socket can cause tissue damage such ... more Introduction: Loading of a residual limb within a prosthetic socket can cause tissue damage such as ulceration. Computational models and simulations may be useful tools for estimating tissue loading within the socket and thus provide insights into how interventions (e.g. prosthesis designs or rehabilitation techniques) affect residual limb-socket interface dynamics. The purpose of this study was to model and simulate residual limb-socket interface dynamics and evaluate the effects of varied prosthesis stiffness on interface dynamics during gait. Methods: A spatial contact model of a residual limb-socket interface was developed and integrated into a gait model with a below-knee amputation. Gait trials were simulated for four subjects walking with low, medium, and high prosthesis stiffness settings. The effects of prosthesis stiffness on interface kinematics, normal pressure, and shear stresses were evaluated. Mean group responses and a subject-specific case study were analyzed. Resul...
Computational Tools and Techniques for Biomedical Signal Processing
Signal processing in biomedical engineering is essentially required for classification while serv... more Signal processing in biomedical engineering is essentially required for classification while serving mainly two aims. The first is noise removal and the second is signal representation. Signal representation deals with transforming the signal in such a way that the signal is most informative in that particular domain for the application at hand. This chapter will describe signal processing methods like spectrogram with specific applications to locomotion and transition classification using Electromyography (EMG) data. A wavelet analysis application on foot acceleration signals for automatic identification of toe off in locomotion and the ramp transition is also shown. Finally, the performance of EMG and accelerometer performance across different time windows of a gait cycle in locomotion and transition classification is presented with an emphasis on fusing the data from both sensors for better classification.
ASME 2012 Summer Bioengineering Conference, Parts A and B, 2012
ABSTRACT Matching a prosthetic foot to meet the activity requirements of the user can be a diffic... more ABSTRACT Matching a prosthetic foot to meet the activity requirements of the user can be a difficult process. The ideal stiffness characteristics of different functional activities may vary. This variation dictates that the prescribed foot must be a compromise of multiple ideals due to functional necessity. The effects of lower limb stiffness have been studied in regards to their ability to reproduce “normal” lower limb mechanics [1,2]. Other studies have tracked gait stability and performance measures for lower limb amputees during gait initiation and termination [3–5]. However, it remains unknown what effects prosthetic stiffness may have on amputee function during gait initiation and termination. The objective of this study was to compare the effects of different component stiffness ranges on locomotion and stability measures during gait initiation and termination
The development of lightweight portable sensors and algorithms for the identification of gait eve... more The development of lightweight portable sensors and algorithms for the identification of gait events at steady-state running speeds can be translated into the real-world environment. However, the output of these algorithms needs to be validated. The purpose of this study was to validate the identification of running gait events using data from Inertial Measurement Units (IMUs) in a semi-uncontrolled environment. Fifteen healthy runners were recruited for this study, with varied running experience and age. Force-sensing insoles measured normal foot-shoe forces and provided a standard for identification of gait events. Three IMUs were mounted to the participant, two bilaterally on the dorsal aspect of the foot and one clipped to the back of each participant’s waistband, approximating their sacrum. The identification of gait events from the foot-mounted IMU was more accurate than from the sacral-mounted IMU. At running speeds <3.57 m s−1, the sacral-mounted IMU identified contact du...
Wearable sensors and machine learning algorithms are becoming a viable alternative for biomechani... more Wearable sensors and machine learning algorithms are becoming a viable alternative for biomechanical analysis outside of the laboratory. The purpose of this work was to estimate gait events from inertial measurement units (IMUs) and utilize machine learning for the estimation of ground reaction force (GRF) waveforms. Sixteen healthy runners were recruited for this study, with varied running experience. Force sensing insoles were used to measure normal foot-shoe forces, providing a proxy for vertical GRF and a standard for the identification of gait events. Three IMUs were mounted on each participant, two bilaterally on the dorsal aspect of each foot and one clipped to the back of each participant’s waistband, approximating their sacrum. Participants also wore a GPS watch to record elevation and velocity. A Bidirectional Long Short Term Memory Network (BD-LSTM) was used to estimate GRF waveforms from inertial waveforms. Gait event estimation from both IMU data and machine learning al...
Progression of age can influence gait characteristics. Previous research has investigated lower e... more Progression of age can influence gait characteristics. Previous research has investigated lower extremity joint mechanics between young and elderly people in locomotion, however little is known about whether differences exist between young and middle age people. Ten young healthy subjects (22.8 ± 5.3 years) and ten middle age healthy subjects (50.7 ± 6.0 years) engaged in treadmill walking (from 0.8 to 2.0 m/s) and running (from 1.8 to 3.8 m/s). The middle age group had higher ankle plantar flexor moment angular impulse (p = 0.002), total support moment impulse (p = 0.016), and hip stance positive work (p = 0.029) across walking speeds. Additionally, the middle age group had higher knee flexion angle at ground contact in walking (p = 0.005) and running (p = 0.037). These findings indicate that moderate age affects changes in ankle and hip kinetic characteristics in walking, and knee kinematic patterns in both walking and running.
INTRODUCTION Fly fishing has long been a popular form of recreation among outdoor enthusiasts, an... more INTRODUCTION Fly fishing has long been a popular form of recreation among outdoor enthusiasts, and is increasing in popularity internationally. A recent study revealed shoulder and elbow pathologies associated with repetitive, high velocity, overhand movements common to fly-casting [1]. However, no study has formally documented the upper extremity movement patterns during fly-casting. The aim of this study was to determine kinematic patterns of the fly-casting stroke. Documenting the movement patterns common to fly-casting will allow greater understanding of the underlying mechanisms of upper extremity pathologies.
Passive energy storage and return (ESR) feet are current performance standard in lower limb prost... more Passive energy storage and return (ESR) feet are current performance standard in lower limb prostheses. A recently developed semi-active variable-stiffness foot (VSF) prosthesis balances the simplicity of a passive ESR device with the adaptability of a powered design. The purpose of this study was to model and simulate the ESR properties of the VSF prosthesis. The ESR properties of the VSF were modeled as a lumped parameter overhung beam. The overhung length is variable, allowing the model to exhibit variable ESR stiffness. Foot-ground contact was modeled using sphere-to-plane contact models. Contact parameters were optimized to represent the geometry and dynamics of the VSF and its foam base. Static compression tests and gait were simulated. Simulation outcomes were compared to corresponding experimental data. Stiffness of the model matched that of the physical VSF (R2: 0.98, root-mean-squared error (RMSE): 1.37 N/mm). Model-predicted resultant ground reaction force (GRFR) matched ...
The hip and ankle strategies that affect learning of a novel gait have not been fully determined,... more The hip and ankle strategies that affect learning of a novel gait have not been fully determined, and could be of importance in design of clinical gait interventions. The authors' purpose was to determine the effects of asymmetric split-belt treadmill walking on ankle and hip work during propulsion. Participants were randomized into either a gradual training group or a sudden training group and later returned for a retention test. The gradual training group performed significantly more work at the hip joint of the slow limb during acquisition, and decreased the hip joint work performed during retention. These findings reveal the hip joint on the slow limb during initial swing as a possible site of adaptation to a novel locomotor pattern.
When humans make errors in stepping during walking due to a perturbation, they may adapt their ga... more When humans make errors in stepping during walking due to a perturbation, they may adapt their gait as a way to correct for discrepancies between predicted and actual sensory feedback. This study sought to determine if increased contextual interference during acquisition of a novel asymmetric gait pattern would change lower-limb mechanical strategies generalized to different walking contexts. Such knowledge could help to clarify the role of contextual interference in locomotor adaptation, and demonstrate potential use in future gait rehabilitation paradigms. One belt on a split-belt treadmill was driven at a constant velocity while the other was driven at changing velocities according to one of three practice paradigms: serial, random blocked, or random training. Subjects returned to complete one of two different transfer tests. Results indicate that during acquisition, random practice requires unique gait mechanics to adapt to a challenging walking environment. Also, results from o...
INTRODUCTION Several studies have attempted prediction of traumatic falls in the elderly, with mi... more INTRODUCTION Several studies have attempted prediction of traumatic falls in the elderly, with mixed results. One study included self-reports of imbalance, a history of falls, and measures of function in daily living, reporting prediction accuracy up to 79% [1]. Another model restricted selection of predictive variables to measures of static posture [2], neglecting dynamic measures of balance function during locomotion.
Gait patterns of the elderly are often adjusted to accommodate for reduced function in the balanc... more Gait patterns of the elderly are often adjusted to accommodate for reduced function in the balance control system. Recent work has demonstrated the effectiveness of artificial neural network (ANN) modeling in mapping gait measurements onto descriptions of whole body motion during locomotion. Accurate risk assessment is necessary for reducing incidence of falls. Further development of the balance estimation model has been used to test the feasibility of detecting balance impairment using tasks of sample categorization and falls risk estimation. Model design included an ANN and a statistical discrimination method. Sample categorization results reached accuracy of 0.89. Relative risk was frequently assessed at high or very high risk for experiencing falls in a sample of balance impaired older adults. The current model shows potential for detecting balance impairment and estimating falls risk, thereby indicating the need for referral for falls prevention intervention.
Zero-velocity assumption has been used for estimation of foot trajectory and stride length during... more Zero-velocity assumption has been used for estimation of foot trajectory and stride length during running from the data of foot-mounted inertial measurement units (IMUs). Although the assumption provides a reasonable initialization for foot trajectory and stride length estimation, the other source of errors related to the IMU’s orientation still remains. The purpose of this study was to develop an improved foot trajectory and stride length estimation method for the level ground running based on the displacement of the foot. Seventy-nine runners performed running trials at 5 different paces and their running motions were captured using a motion capture system. The accelerations and angular velocities of left and right feet were measured with two IMUs mounted on the dorsum of each foot. In this study, foot trajectory and stride length were estimated using zero-velocity assumption with IMU data, and the orientation of IMU was estimated to calculate the mediolateral and vertical distanc...
Introduction: Loading of a residual limb within a prosthetic socket can cause tissue damage such ... more Introduction: Loading of a residual limb within a prosthetic socket can cause tissue damage such as ulceration. Computational models and simulations may be useful tools for estimating tissue loading within the socket and thus provide insights into how interventions (e.g. prosthesis designs or rehabilitation techniques) affect residual limb-socket interface dynamics. The purpose of this study was to model and simulate residual limb-socket interface dynamics and evaluate the effects of varied prosthesis stiffness on interface dynamics during gait. Methods: A spatial contact model of a residual limb-socket interface was developed and integrated into a gait model with a below-knee amputation. Gait trials were simulated for four subjects walking with low, medium, and high prosthesis stiffness settings. The effects of prosthesis stiffness on interface kinematics, normal pressure, and shear stresses were evaluated. Mean group responses and a subject-specific case study were analyzed. Resul...
Computational Tools and Techniques for Biomedical Signal Processing
Signal processing in biomedical engineering is essentially required for classification while serv... more Signal processing in biomedical engineering is essentially required for classification while serving mainly two aims. The first is noise removal and the second is signal representation. Signal representation deals with transforming the signal in such a way that the signal is most informative in that particular domain for the application at hand. This chapter will describe signal processing methods like spectrogram with specific applications to locomotion and transition classification using Electromyography (EMG) data. A wavelet analysis application on foot acceleration signals for automatic identification of toe off in locomotion and the ramp transition is also shown. Finally, the performance of EMG and accelerometer performance across different time windows of a gait cycle in locomotion and transition classification is presented with an emphasis on fusing the data from both sensors for better classification.
ASME 2012 Summer Bioengineering Conference, Parts A and B, 2012
ABSTRACT Matching a prosthetic foot to meet the activity requirements of the user can be a diffic... more ABSTRACT Matching a prosthetic foot to meet the activity requirements of the user can be a difficult process. The ideal stiffness characteristics of different functional activities may vary. This variation dictates that the prescribed foot must be a compromise of multiple ideals due to functional necessity. The effects of lower limb stiffness have been studied in regards to their ability to reproduce “normal” lower limb mechanics [1,2]. Other studies have tracked gait stability and performance measures for lower limb amputees during gait initiation and termination [3–5]. However, it remains unknown what effects prosthetic stiffness may have on amputee function during gait initiation and termination. The objective of this study was to compare the effects of different component stiffness ranges on locomotion and stability measures during gait initiation and termination
The development of lightweight portable sensors and algorithms for the identification of gait eve... more The development of lightweight portable sensors and algorithms for the identification of gait events at steady-state running speeds can be translated into the real-world environment. However, the output of these algorithms needs to be validated. The purpose of this study was to validate the identification of running gait events using data from Inertial Measurement Units (IMUs) in a semi-uncontrolled environment. Fifteen healthy runners were recruited for this study, with varied running experience and age. Force-sensing insoles measured normal foot-shoe forces and provided a standard for identification of gait events. Three IMUs were mounted to the participant, two bilaterally on the dorsal aspect of the foot and one clipped to the back of each participant’s waistband, approximating their sacrum. The identification of gait events from the foot-mounted IMU was more accurate than from the sacral-mounted IMU. At running speeds <3.57 m s−1, the sacral-mounted IMU identified contact du...
Wearable sensors and machine learning algorithms are becoming a viable alternative for biomechani... more Wearable sensors and machine learning algorithms are becoming a viable alternative for biomechanical analysis outside of the laboratory. The purpose of this work was to estimate gait events from inertial measurement units (IMUs) and utilize machine learning for the estimation of ground reaction force (GRF) waveforms. Sixteen healthy runners were recruited for this study, with varied running experience. Force sensing insoles were used to measure normal foot-shoe forces, providing a proxy for vertical GRF and a standard for the identification of gait events. Three IMUs were mounted on each participant, two bilaterally on the dorsal aspect of each foot and one clipped to the back of each participant’s waistband, approximating their sacrum. Participants also wore a GPS watch to record elevation and velocity. A Bidirectional Long Short Term Memory Network (BD-LSTM) was used to estimate GRF waveforms from inertial waveforms. Gait event estimation from both IMU data and machine learning al...
Progression of age can influence gait characteristics. Previous research has investigated lower e... more Progression of age can influence gait characteristics. Previous research has investigated lower extremity joint mechanics between young and elderly people in locomotion, however little is known about whether differences exist between young and middle age people. Ten young healthy subjects (22.8 ± 5.3 years) and ten middle age healthy subjects (50.7 ± 6.0 years) engaged in treadmill walking (from 0.8 to 2.0 m/s) and running (from 1.8 to 3.8 m/s). The middle age group had higher ankle plantar flexor moment angular impulse (p = 0.002), total support moment impulse (p = 0.016), and hip stance positive work (p = 0.029) across walking speeds. Additionally, the middle age group had higher knee flexion angle at ground contact in walking (p = 0.005) and running (p = 0.037). These findings indicate that moderate age affects changes in ankle and hip kinetic characteristics in walking, and knee kinematic patterns in both walking and running.
INTRODUCTION Fly fishing has long been a popular form of recreation among outdoor enthusiasts, an... more INTRODUCTION Fly fishing has long been a popular form of recreation among outdoor enthusiasts, and is increasing in popularity internationally. A recent study revealed shoulder and elbow pathologies associated with repetitive, high velocity, overhand movements common to fly-casting [1]. However, no study has formally documented the upper extremity movement patterns during fly-casting. The aim of this study was to determine kinematic patterns of the fly-casting stroke. Documenting the movement patterns common to fly-casting will allow greater understanding of the underlying mechanisms of upper extremity pathologies.
Passive energy storage and return (ESR) feet are current performance standard in lower limb prost... more Passive energy storage and return (ESR) feet are current performance standard in lower limb prostheses. A recently developed semi-active variable-stiffness foot (VSF) prosthesis balances the simplicity of a passive ESR device with the adaptability of a powered design. The purpose of this study was to model and simulate the ESR properties of the VSF prosthesis. The ESR properties of the VSF were modeled as a lumped parameter overhung beam. The overhung length is variable, allowing the model to exhibit variable ESR stiffness. Foot-ground contact was modeled using sphere-to-plane contact models. Contact parameters were optimized to represent the geometry and dynamics of the VSF and its foam base. Static compression tests and gait were simulated. Simulation outcomes were compared to corresponding experimental data. Stiffness of the model matched that of the physical VSF (R2: 0.98, root-mean-squared error (RMSE): 1.37 N/mm). Model-predicted resultant ground reaction force (GRFR) matched ...
The hip and ankle strategies that affect learning of a novel gait have not been fully determined,... more The hip and ankle strategies that affect learning of a novel gait have not been fully determined, and could be of importance in design of clinical gait interventions. The authors' purpose was to determine the effects of asymmetric split-belt treadmill walking on ankle and hip work during propulsion. Participants were randomized into either a gradual training group or a sudden training group and later returned for a retention test. The gradual training group performed significantly more work at the hip joint of the slow limb during acquisition, and decreased the hip joint work performed during retention. These findings reveal the hip joint on the slow limb during initial swing as a possible site of adaptation to a novel locomotor pattern.
When humans make errors in stepping during walking due to a perturbation, they may adapt their ga... more When humans make errors in stepping during walking due to a perturbation, they may adapt their gait as a way to correct for discrepancies between predicted and actual sensory feedback. This study sought to determine if increased contextual interference during acquisition of a novel asymmetric gait pattern would change lower-limb mechanical strategies generalized to different walking contexts. Such knowledge could help to clarify the role of contextual interference in locomotor adaptation, and demonstrate potential use in future gait rehabilitation paradigms. One belt on a split-belt treadmill was driven at a constant velocity while the other was driven at changing velocities according to one of three practice paradigms: serial, random blocked, or random training. Subjects returned to complete one of two different transfer tests. Results indicate that during acquisition, random practice requires unique gait mechanics to adapt to a challenging walking environment. Also, results from o...
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