Papers by Young-Hui Chang
Prosthetics & Orthotics International, 2021
Study Design: A mechanical testing protocol was used to compare the material properties of commer... more Study Design: A mechanical testing protocol was used to compare the material properties of commercially available foams with that of a newly designed granular jamming orthosis prototypes. Background: Foot orthoses have an inherent limitation of predetermined mechanical material properties coupled with a fixed orthotic interface shape that cannot be readily changed. Objectives: To develop and test a novel orthotic insole design concept that incorporates principles of granular jamming. Methods: Granular media were used in combination with vacuum pressure to create a variable stiffness granular foot orthosis. Four types of granular media (rice, poppy seeds, micropolystyrene, and polystyrene beads) were tested in different prototype configurations varying in volume fill and particulate size. Stress–strain curves were obtained from uniaxial compression tests to characterize granular foot orthosis prototypes in comparison with commercial orthotic foams. Results: Increasing vacuum pressure...
Background Manual tuning of robotic lower limb prostheses can be time consuming for both the pati... more Background Manual tuning of robotic lower limb prostheses can be time consuming for both the patient and the clinician and requires in-person visits to a clinic. An automated process for the tuning parameters of a robotic lower limb prosthesis could result in a substantial savings in healthcare resources. A critical challenge to an automated parameter tuning algorithm is the quantification of a person’s gait quality. There is not good agreement in the literature of an objective outcome measure that can rapidly assess gait quality in lower limb amputees. As a first step, we investigated the ability of four common gait quality metrics to detect differences in gait quality: Prosthetic Observational Gait Score (POGS), Gait Deviation Index (GDI), Lateral Sway, and Impulse Asymmetry. Methods We systematically applied four unilateral lower limb joint constraint conditions (baseline/no constraint, ankle constraint, knee constraint, and knee + ankle constraint) to nine able-bodied participan...
Journal of Experimental Biology, 1997
We describe a transducer system and analysis strategy that allows the determination of dynamic fo... more We describe a transducer system and analysis strategy that allows the determination of dynamic forces and moments applied by an arm-swinging animal during locomotion. We have employed readily available technology and analysis procedures to produce a low-cost but effective system. The solutions to several problems in the design of the system are provided, and the functional characteristics of the system are demonstrated using both an inert pendulum and an actively brachiating gibbon (Hylobates lar).
Osteoarthritis and Cartilage, 2019
Effects of treadmill running and limb immobilization on knee cartilage degeneration and locomotor... more Effects of treadmill running and limb immobilization on knee cartilage degeneration and locomotor joint kinematics in rats following knee meniscal transection, Osteoarthritis and Cartilage,
Journal of Applied Biomechanics, 2018
Clinically, measuring gait kinematics and ground reaction force (GRF) is useful to determine the ... more Clinically, measuring gait kinematics and ground reaction force (GRF) is useful to determine the effectiveness of treatment. However, it is inconvenient and expensive to maintain a laboratory-grade gait analysis system in most clinics. The purpose of this study was to validate a Wii Balance Board, Kinovea motion-tracking software, and a video camera as a portable, low-cost system, and overground gait analysis system. We validated this low-cost system against a multicamera Vicon system and research-grade force platform (Advanced Mechanical Technology, Inc). After validation trials with known weights and angles, 5 subjects walked across an instrumented walkway for multiple times (n = 8/subject). We collected vertical GRF and segment angles. Average GRF data from the 2 systems were similar, with peak GRF errors below 3.5%BW. However, variability in the balance board’s sampling rate led to large GRF errors early and late in stance, when the GRF changed rapidly. The thigh, shank, and foo...
Journal of Applied Physiology, 1998
We constructed a force treadmill to measure the vertical, horizontal and lateral components of th... more We constructed a force treadmill to measure the vertical, horizontal and lateral components of the ground-reaction forces (Fz, Fy, Fx, respectively) and the ground-reaction force moments (Mz, My, Mx), respectively exerted by walking and running humans. The chassis of a custom-built, lightweight (90 kg), mechanically stiff treadmill was supported along its length by a large commercial force platform. The natural frequencies of vibration were >178 Hz for Fzand >87 Hz for Fy, i.e., well above the signal content of these ground-reaction forces. Mechanical tests and comparisons with data obtained from a force platform runway indicated that the force treadmill recorded Fz, Fy,Mxand Myground-reaction forces and moments accurately. Although the lowest natural frequency of vibration was 88 Hz for Fx, the signal-to-noise ratios for Fxand Mzwere unacceptable. This device greatly decreases the time and laboratory space required for locomotion experiments and clinical evaluations. The modu...
Biology open, Jan 6, 2018
The ability to recover purposeful movement soon after debilitating neuromuscular injury is essent... more The ability to recover purposeful movement soon after debilitating neuromuscular injury is essential to animal survival. Various neural and mechanical mechanisms exist to preserve whole-limb kinematics despite exhibiting long-term deficits of individual joints following peripheral nerve injury. However, it is unclear whether functionally relevant whole-limb movement is acutely conserved following injury. Therefore, the objective of this longitudinal study of the injury response from four individual cats was to test the hypothesis that whole-limb length is conserved following localized nerve injury of ankle extensors in cats with intact nervous systems. The primary finding of our study was that whole-limb kinematics during walking was not immediately preserved following peripheral nerve injuries that paralyzed subsets of ankle extensor muscles. Instead, whole-limb kinematics recovered gradually over multiple weeks, despite having the mechanical capacity of injury-spared muscles acros...
Journal of Applied Physiology, 1999
Previous studies have suggested that generating vertical force on the ground to support body weig... more Previous studies have suggested that generating vertical force on the ground to support body weight (BWt) is the major determinant of the metabolic cost of running. Because horizontal forces exerted on the ground are often an order of magnitude smaller than vertical forces, some have reasoned that they have negligible cost. Using applied horizontal forces (AHF; negative is impeding, positive is aiding) equal to −6, −3, 0, +3, +6, +9, +12, and +15% of BWt, we estimated the cost of generating horizontal forces while subjects were running at 3.3 m/s. We measured rates of oxygen consumption (V˙o2) for eight subjects. We then used a force-measuring treadmill to measure ground reaction forces from another eight subjects. With an AHF of −6% BWt,V˙o2increased 30% compared with normal running, presumably because of the extra work involved. With an AHF of +15% BWt, the subjects exerted ∼70% less propulsive impulse and exhibited a 33% reduction inV˙o2. Our data suggest that generating horizont...
The Journal of experimental biology, Jan 8, 2017
Minimizing whole body metabolic cost has been suggested to drive the neural processes of locomoto... more Minimizing whole body metabolic cost has been suggested to drive the neural processes of locomotor adaptation. Mechanical work performed by the legs should dictate the major changes in whole body metabolic cost of walking while providing greater insight into temporal and spatial mechanisms of adaptation. We hypothesized changes in mechanical work by the legs during an asymmetric split-belt walking adaptation task could explain previously observed changes in whole body metabolic cost. We predicted subjects would immediately increase mechanical work performed by the legs when first exposed to split-belt walking, followed by a gradual decrease throughout adaptation. Fourteen subjects walked on a dual-belt, instrumented treadmill. Baseline trials were followed by a ten-minute split-belt adaptation condition with one belt running three times faster than the other. A post-adaptation trial with both belts moving at 0.5m/s demonstrated neural adaptation. As predicted, summed mechanical work...
Encyclopedia of Computational Neuroscience, 2014
Journal of neurophysiology, 2015
During movement, errors are typically corrected only if they hinder performance. Preferential cor... more During movement, errors are typically corrected only if they hinder performance. Preferential correction of task-relevant deviations is described by the minimal intervention principle but has not been demonstrated in the joints during locomotor adaptation. We studied hopping as a tractable model of locomotor adaptation of the joints within the context of a limb-force-specific task space. Subjects hopped while adapting to shifted visual feedback that induced them to increase peak ground reaction force (GRF). We hypothesized subjects would preferentially reduce task-relevant joint torque deviations over task-irrelevant deviations to increase peak GRF. We employed a modified uncontrolled manifold analysis to quantify task-relevant and task-irrelevant joint torque deviations for each individual hop cycle. As would be expected by the explicit goal of the task, peak GRF errors decreased in early adaptation before reaching steady state during late adaptation. Interestingly, during the earl...
Journal of advanced smart convergence, 2012
The conventional method for filtering force plate data, low-pass filtering, does not always give ... more The conventional method for filtering force plate data, low-pass filtering, does not always give accurate results when applied to force data from a custom-made, instrumented treadmill. Therefore, this study compares low-pass filtered data to the same data passed through a wavelet filter. We collected data with the treadmill running. However these include motor noise with ground reaction force at two force plates. We found that he proposed wavelet method eliminated motor noise to result in more accurate force plate data than the conventional low-pass filter, particularly at high speed motor operation. In this study we suggested the convolution wavelet (CNW) which was compared to that of a low-pass filter. The CNW showed better performance as compared to band-pass filtering particularly for low signal-to-noise ratios, and a lower computational load.
1993 IEEE Annual Northeast Bioengineering Conference
Surface strains recorded from multiple rosette gauges at different sites on the left forehooves o... more Surface strains recorded from multiple rosette gauges at different sites on the left forehooves of horses and donkeys during walks at 1.8 m/s are discussed. The strain pattern of the wall was manipulated by adding 12 mm cleat wedges to the heels of the horseshoes. Principal strains were repeatable for each gauge site and cleat situation on an individual. Substantial inter-individual variation existed. Peak principal strains were always in compression. Under normal circumstances (no cleats attached) peak strains were on the order of 1000-3000 με, depending on gauge site. Biaxial compression dominated in the wall, but the degree of horizontal compression was reduced by altering the mediolateral balance of the foot. The strain pattern of the hoof wall correlates well with the complex fiber orientation of the wall material and appears to result from well coordinated distortion of different regions of the structure
Journal of Neuroscience Methods, 2010
The sophistication of current rodent injury and disease models outpaces that of the most commonly... more The sophistication of current rodent injury and disease models outpaces that of the most commonly used behavioral assays. The first objective of this study was to measure rat locomotion using highspeed x-ray video to establish an accurate baseline for rat hindlimb kinematics. The second objective was to quantify the kinematics errors due to skin movement artefacts by simultaneously recording and comparing hindlimb kinematics derived from skin markers and from direct visualization of skeletal landmarks. Joint angle calculations from skin-derived kinematics yielded errors as high as 39° in the knee and 31° in the hip around paw contact with respect to the x-ray data. Triangulation of knee position from the ankle and hip skin markers provided closer, albeit still inaccurate, approximations of bone-derived, x-ray kinematics. We found that soft tissue movement errors are the result of multiple factors, the most impressive of which is overall limb posture. Treadmill speed had surprisingly little effect on kinematics errors. These findings illustrate the significance and context of skin movement error in rodent kinematics.
Frontiers in Bioscience, 2012
Introduction 2.1. The neonatal rodent spinal cord maintained in vitro for studies on locomotion 2... more Introduction 2.1. The neonatal rodent spinal cord maintained in vitro for studies on locomotion 2.2. Provision of a MATLAB-based code to analyze important measures of locomotion 3. Afferent activity-based recruitment, modulation and feedback control of locomotion 3.1. Introduction 3.2. General methods 3.3. Effects of sacral dorsal column stimulation on activated locomotor-like activity 3.4. Effects of sacral dorsal column stimulation during ongoing neurochemical locomotion 3.5. Afferent stimulation in closed-loop feedback strategies for locomotor control 4. Methodologies to study circuit operation with intact hindlimbs: The in vitro spinal cord hindlimbs-restrained preparation 4.1. Introduction 4.2. General methods 4.3. Recording muscle EMG recruitment patterns during locomotion: complex phasing and expression of spontaneous burst deletions 4.4. Afferent activity can perturb ongoing locomotion: Activation of nociceptive flexion reflexes 5. Methodologies to study circuit operation with intact hindlimbs: Unrestrained hindlimb locomotion. 5.1. Introduction 5.2. General methods 5.3. Studies on sensory modulation and reinforcement in the spinal cord-hindlimbs pendant preparation 5.4. Intracellular recordings during unrestrained hindlimb stepping in the spinal cord-hindlimbs pendant preparation 6. Conclusions 7. Acknowledgements 8. References
Experimental Brain Research, 2009
Biology Letters, 2013
Locomotion persists across all manner of internal and external perturbations. The objective of th... more Locomotion persists across all manner of internal and external perturbations. The objective of this study was to identify locomotor compensation strategies in rodent models of peripheral nerve injury. We found that hip-to-toe limb length and limb angle was preferentially preserved over individual joint angles after permanent denervation of rat ankle extensor muscles. These findings promote further enquiry into the significance of limb-level function for neuromechanical control of legged locomotion.
American Journal of Physical Anthropology, 2001
How do arm‐swinging apes locomote effectively over a variety of speeds? One way to reduce the met... more How do arm‐swinging apes locomote effectively over a variety of speeds? One way to reduce the metabolic energy cost of locomotion is to transfer energy between reversible mechanical modes. In terrestrial animals, at least two transfer mechanisms have been identified: 1) a pendulum‐like mechanism for walking, with exchange between gravitational potential energy and translational kinetic energy, and 2) a spring‐like mechanism for running, where the elastic strain energy of stretched muscle and tendon is largely returned to reaccelerate the animal. At slower speeds, a brachiator will always have at least one limb in contact with the support, similar to the overlap of foot contact in bipedal walking. At faster speeds, brachiators exhibit an aerial phase, similar to that seen in bipedal running. Are there two distinct brachiation gaits even though the animal appears to simply swing beneath its overhead support? If so, are different exchange mechanisms employed? Our kinetic analysis of br...
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Papers by Young-Hui Chang