Download or read book Evaluating Use of a Robotic Prosthetic Foot Emulator to Test drive Prosthetic Feet in People with Lower Limb Amputation written by Elizabeth Gabrielle Halsne and published by . This book was released on 2021 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: Selection of a prosthetic foot is an important decision for lower limb prosthesis prescription. Without objective evidence to guide foot prescription, clinicians (i.e., physicians and prosthetists) rely on their expertise to best match a foot to a patient’s functional goals. However, persons with lower limb amputation typically cannot usually try different prosthetic feet before one is ultimately selected. The robotic prosthetic foot emulator (PFE) is a technological advancement that could facilitate a test-driving approach to foot selection, in which the prosthesis user quickly trials several prosthetic feet and then contributes their experiential input to the decision-making process. This dissertation used quantitative and qualitative approaches to assess use of the PFE for test-driving prosthetic feet. First, quantitative procedures to emulate the angular stiffness of commercial feet used in the PFE were developed and validated. Mechanical testing procedures were used to collect angular stiffness data for a variety of commercial prosthetic forefeet. PFE foot profiles were created from these data and mechanical testing was repeated with the emulated feet to evaluate the accuracy of the emulation. Angular stiffness of emulated feet was significantly correlated with that of respective commercial feet. Mean differences in angular stiffness between emulated and commercial feet were less than 1%, and were independent of prosthetic foot type and example foot sizes or intended user body weights. Participants with lower limb amputation (LLA) then used both the PFE and commercial feet to complete a test-driving protocol, before completing qualitative, semi-structured interviews with an investigator. The purpose of the interviews was to develop a grounded theory of the experience of prosthetic foot prescription from the perspective of prosthesis users. The core category was the relationship between knowledge about prosthetic feet and decision-making power. Participants described prosthetic foot prescription as an educational journey. Relationships with clinicians and peers with LLA were recognized as highly valued and capable of influencing the quality of the foot prescription experience. Participants also noted the importance of their individuality and preferences for the extent of being engaged in decision-making. Test-driving accelerated users’ education about feet options and facilitated discussion with clinicians. Therefore, complementary findings from these two studies support the potential for future use of the PFE for test-driving. Further research may be warranted to evaluate the use of the PFE and test-driving to augment prosthetic foot prescription processes.

Download or read book Design of a Novel Mechatronic System to Test Prosthetic Feet Under Specific Walking Activity Loads and Evaluate Their Lower Leg Trajectory Error written by Heidi V. Peterson and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lower limb amputees, numbered at more than 40 million globally, are challenged with limited mobility due to prosthetic devices that do not fully restore the functionalities of their biological limbs. While commercially available energy storage and return feet do restore some of the functionalities of a missing limb, the development and use of these prosthetic devices are limited by the current design, evaluation, and prescription processes. This is because the connection between the combined mechanical characteristics of a foot and user outcomes, such as mobility, comfort, and walking effort, is not fully understood. The lower leg trajectory error (LLTE) is a novel prosthetic foot performance metric that provides a quantitative connection between the mechanical characteristics of a foot and the expected gait of an amputee. Thus far, the LLTE value of a foot has only been calculated via simulation, which limits the practical use of the metric in prosthetic foot design, evaluation, and prescription. One way to systematically measure the LLTE value of a physical prosthetic foot would be through a mechanical bench test, but the capabilities of existing bench testing devices are insufficient due to limited degrees of actuation and reported accuracy. The purpose of this work was to design the Prosthetic Foot Testing Device (PFTD), a mechatronic testing device that could apply specific and uncoupled GRFs to any CoP on a foot and measure its deflection, through which it could measure the LLTE value and thus predict walking performance of any passive prosthetic foot. First, we determined high-level functional requirements of the PFTD, including the ranges of reference loads and prosthetic foot deflections as well as the LLTE measurement accuracy, such that the PFTD could meaningfully measure the full range of commercially available prosthetic feet. Second, we derived the relationships between the variables used to calculate the LLTE metric and those controlled or measured by the PFTD. Third, we used these relationships to design the PFTD and perform sensitivity analysis to ensure it could meaningfully and accurately measure the LLTE value of any passive prosthetic foot. In future work, the PFTD will be built, validated, and used to measure and compare the LLTE values of various prosthetic feet. The PFTD and theory presented herein may become a new tool in the prosthetics industry to systematically and amputee-independently measure and compare the performance of prosthetic devices using the LLTE value as a universal metric, which could ultimately improve the development and prescription processes of prostheses.

Download or read book Experimental Validation of the Lower Leg Trajectory Error an Optimization Metric for Prosthetic Feet written by Victor Prost (S.M.) and published by . This book was released on 2017 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: In India alone, there are about one million people with lower limb amputation who require significantly more effort to walk than able-bodied individuals. They are subject to social stigmas preventing them from employment and independent living. There is a gap between the high-performance prosthetic feet in the United States that come at a cost of thousands of dollars and affordable prostheses in the developing world, which lack quality, durability and performance. The aim of this project was to design a high-performance, mass-manufacturable passive prosthetic foot for Indian amputees that complies with international standards at an affordable cost. This work was conducted in collaboration with Bhagwan Mahaveer Viklang Sahayata Samiti (BMVSS, the Jaipur Foot organization), in Jaipur, India. Through a novel, quantitative method called Lower Leg Trajectory Error (LLTE) which maps the mechanical design of a prosthetic foot to its biomechanical performance, we can optimize the compliance and geometry of a passive prosthesis to replicate able-bodied gait and loading on the foot using affordable materials. This thesis is focused on evaluating the accuracy and validity of the LLTE as a novel design tool. To validate feet designed using the LLTE, field trials and clinical testing were performed on prosthetic feet prototypes with varying stiffnesses and geometries. The novel merits of these prototypes are that they can replicate a similar quasi-stiffness and range of motion of a physiological ankle using interchangeable custom U-shaped constant stiffness springs ranging from 1.5 to 24 Nm/deg and having up to 30' of range of motion. Initial testing conducted using these feet validated the consitutive model of the LLTE and suggested that prosthetic feet designed with lower LLTE values could offer benefits to the user. In future work, the validated design tool will be used to create high-performance, low-cost and mass-manufacturable prosthetic feet for amputees, throughout the developing world and in the developed world.

Download or read book Effectiveness Evaluation and Functional Theoretical Modeling of Dynamic Elastic Response Lower Limb Prosthetics written by Mark Daniel Geil and published by . This book was released on 1997 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Advances in materials technology have brought about a class of prosthetic foot and ankle components for the lower limb amputee, called Dynamic Elastic Response (DER). These components are designed to store energy during the stance phase of gait in a leaf spring keel, and return a portion of the stored energy at the end of stance phase to contribute to the forward progression of the limb. This energy storage and return is designed to partially replace the push-off of active ankle plantarflexor muscles in late stance. Typical subjective responses to DER feet are favorable. However, the majority of research investigations seeking to compare different DER designs have concluded that the feet offer no advantage over a conventional lower limb prosthesis. One goal of this research is to improve upon several of the techniques used in the literature to evaluate DER feet, contributing to a better understanding of their function. The second goal of this research is the complete characterization of the material properties of an existing DER foot with the eventual goal of functional theoretical modeling to serve alternative amputee populations, including the largest patient group of elderly amputees secondary to peripheral vascular disease or diabetic neuropathy. Materials testing was performed on the DER foot in question, the Carbon Copy High Performance (HP), to determine model inputs and to evaluate the errors in the common processing method, inverse dynamics. Results indicated hysteresis in the foot structure not accounted for by inverse dynamics as well as cantilever beam deformation in the anterior of the foot apart from the anatomical ankle joint, another deficiency with the standard approach. A new method is proposed to calculate energy storage and return, utilizing power flow into the proximal foot and out of the distal foot. The method contains several theoretical advantages over existing techniques. Material properties of the foot deformation plates and the surrounding cosmetic foam were quantified and formulated into coefficients appropriate for a rigid-body model. The foot geometry was characterized through a novel set of imaging and processing techniques to enable the accurate representation of geometry in the model.

Download or read book Development and Validation of a Passive Prosthetic Foot Design Framework Based on Lower Leg Dynamics written by Victor Prost and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: People with lower limb amputations face considerable challenges to everyday mobility that affect their quality of life. This is especially the case in low and middle income countries (LMIC) where the lack of affordable high-performance prosthetic devices forces people to use inadequate limbs that require more effort and exhibit unnatural walking motions. This thesis develops methods for designing customized, high-performance, low-cost, and durable passive prosthetic feet that enable users to replicate able-bodied walking patterns. The current development process of prosthetic feet relies on extensive user testing and iterative design rather than a predictive and quantitative design methodology that would facilitate the development of improved prosthetic devices. Here, we further developed the lower leg trajectory error (LLTE) framework, a novel design methodology that connects the mechanical characteristics of a prosthetic foot to the user's walking pattern. We extended the methodology to describe the entire prosthetic step for multiple walking activities and foot architectures, including durability requirements, and efficient constitutive modelling of prosthetic foot designs. These developments resulted in more than a two-fold improvement in the walking performance of LLTE-designed prosthetic feet that fulfilled the international standards durability requirements, and a ten-times reduction in computational time compared to the original LLTE methodology. The LLTE design framework and foot architectures described in this work should provide designers, engineers, and clinicians with a practical, predictive, and quantitative tool for designing and evaluating prosthetic feet. Using the LLTE framework, low-cost, customized passive prosthetic feet prototypes were designed and clinically evaluated for level ground walking against conventional carbon fiber prostheses. The LLTE feet performed as predicted with no iteration for a wide variety of patients. In addition, these prosthetic feet demonstrated 14% closer replication of able-bodied walking motion, 46% higher propulsion, 13% lower peak leg loading, and higher user preference compared to a standard commercial carbon fiber foot for less than a tenth of its cost. These results suggest that the LLTE framework can be used to design customized, low-cost prostheses that enable able-bodied walking pattern, with reduced effort and risk of long-term injuries. A systematic sensitivity investigation of five foot prototypes designed using the LLTE framework showed that users' most closely replicated the target able-bodied walking pattern with the predicted LLTE-optimal foot, experimentally demonstrating that the predicted optimum was a true optimum. In addition, the predicted LLTE performance of the prototype feet was correlated to the user's ability to replicate the target walking pattern, user's preference, and conventional clinical outcomes. This sensitivity study illustrated the utility of the LLTE framework as an systematic and robust evaluation methodology for prosthetic feet, potentially improving the development and prescription of prosthetic devices. A rugged prosthetic foot with a cosmetic overmold was also designed using the LLTE framework to accommodate the economic, environmental, and cultural requirements for users in India. The foot was distributed to 16 prosthetic users in India to be used for several months. Users walked 16% faster with the foot compared to their daily-use prosthesis, the Jaipur foot, and commented on the reduced effort of walking. The rugged foot endured one million cycles of fatigue testing, and the wear and tear of daily living without alterations in its mechanical performance. This mass-manufacturable, high-performance rugged foot could replace conventional feet used in low-resource settings and significantly improve the mobility and quality of life of LMIC prosthesis users.

Download or read book Biomechanical Evaluation of Prosthetic Feet written by James C. H. Goh and published by . This book was released on 1982 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An evaluation method was developed which can be used generally for the assessment of any prosthetic feet. The two most common prosthetic feet prescribed to below-knee and above-knee amputees are the Uniaxial and SACH feet. A review of prescription practices shows that in the United Kingdom about 80% of the below-knee and above-knee amputees are fitted with a Uniaxial foot, whereas in the United States about 80% are fitted with the SACH foot. These contradictory prescription practices between the two countries, prompted the project to be concentrated on the evaluation of the SACH and Uniaxial feet. The method developed includes a subjective assessment procedure and a biomechanical evaluation on the function of the two prosthetic feet and their effects on whole body gait kinematics and lower limb kinetics. A review of the methods used in gait analysis is presented in the thesis. This forms a basis for the selection of a suitable gait recording system for the project. A background study of lower limb prosthetics in general and a review of prosthetic ankle/foot assemblies in particular are also presented. The methodology and instrumentation used in the project are given. Altogether, six below-knee and five above-knee amputees were tested. Due to insufficient supply of heel bumper stiffness by the manufacturer for the Uniaxial foot, heel bumpers of varying stiffnesses had to be made in the Bioengineering Unit. The development of the analytical procedure for the three-dimensional analysis is presented. A suite of computer programs was written to facilitate the handling of the large amount of data, details of which are included in the Appendix. Results from the analysis of the tests performed are discussed. Although some apparent differences were observed between the SACH and Uniaxial feet, no conclusion can be drawn as to which is better for the function of the amputee.

Download or read book Biomechanical Evaluation of Prosthetic Feet written by C. H. James and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Analysis and Computational Simulation of Unilateral Transtibial Amputee Walking to Evaluate Prosthetic Device Design Characteristics and Amputee Gait Mechanics written by Jessica Dawn Ventura and published by . This book was released on 2010 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over one million amputees are living in the United States with major lower limb loss (Ziegler-Graham et al. 2008). Lower limb amputation leads to the functional loss of the ankle plantar flexor muscles, which are important contributors to body support, forward propulsion, and leg swing initiation during walking (Neptune et al. 2001; Liu et al. 2006). Effective prosthetic component design is essential for successful rehabilitation of amputees to return to an active lifestyle by partially replacing the functional role of the ankle muscles. The series of experimental and computer simulation studies presented in this research showed that design characteristics of energy storage and return prosthetic ankles, specifically the elastic stiffness, significantly influence residual and intact leg ground reaction forces, knee joint moments, and muscle activity, thus affecting muscle output. These findings highlight the importance of proper prosthetic foot stiffness prescription for amputees to assure effective rehabilitation outcomes. The research also showed that the ankle muscles serve to stabilize the body during turning the center of mass. When amputees turn while supported by their prosthetic components, they rely more on gravity to redirect the center of mass than active muscle generation. This mechanism increases the risks of falling and identifies a need for prosthetic components and rehabilitation focused on increasing amputee stability during turning. A proper understanding of the effects of prosthetic components on amputee walking mechanics is critical to decreasing complications and risks that are prevalent among lower-limb amputees. The presented research is an important step towards reaching this goal.

Download or read book Performance Evaluation of Man machine Systems written by Siddhartha Ganguli and published by . This book was released on 1982 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Generative Design of an Additively Manufactured Passive Prosthetic Foot for Multiple Forms of Ambulation written by Megan McGuire and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over 2.1 million people in the United States are living with limb loss. The majority of those individuals have a loss of a lower limb (Ziegler‐Graham et al, 2008), and over 150,000 people undergo lower limb amputation per year (Dillingham et al, 2005; Owings et al, 1996). Those with transtibial or transfemoral limb loss utilize lower-limb prostheses, which commonly includes a passive prosthetic foot. Prosthetic feet can be costly, limited in their functionality, and can be difficult to integrate with the addition of a sock, prosthetic cover (i.e. shell), and shoe. This study explores the use of computer-aided generative design to create usable additively manufactured (AM) mechanically-passive prosthetic feet that are optimized for multiple forms of ambulation including level, upstairs, downstairs, and sloped walking. Using the generative design framework, the foot is not only optimized for safety during multiple forms of ambulation, but also redesigned for reduced mass and cost using AM, as well as greater ease of use – forgoing the need for a separate shell or shoe by combining the prosthetic foot and customized sole into a single integrated unit. The result of this design study is a customizable 3D-printed foot model and sole, verified for safety through compressive loads to simulate multiple ambulation tasks, as well as different phase within these tasks. The models were tested against existing carbon fiber and 3D printed passive foot models, with and without a shell and shoe, under compression to simulate different forms of ambulation. For these conditions, we evaluate stiffness profiles and failure modes experimentally, as well as examine the distributions of stress and displacement within the finite element simulations of the generative design to understand how these designs function during different phases and modes of ambulation. This creation and validation of an AM, customizable foot and shoe prosthetic could open the door for the increased accessibility and performance of foot prostheses, as well as improve the quality of life for lower-limb amputees

Download or read book Bulletin of Prosthetics Research written by and published by . This book was released on 1968 with total page 1330 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Interfacing Humans and Machines for Rehabilitation and Assistive Devices written by Carlos A. Cifuentes and published by Frontiers Media SA. This book was released on 2022-01-24 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dr Jan Veneman is employed by Hocoma AG. All other Topic Editors declare no competing interests with regards to the Research Topic subject.

Download or read book Design and Evaluation of a Cantilever Beam type Prosthetic Foot for Indian Persons with Amputations written by Kathryn M. Olesnavage and published by . This book was released on 2014 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this work is to design a low cost, high performance prosthetic foot in collaboration with Bhagwan Mahaveer Viklang Sahayata Samiti (BMVSS), in Jaipur, India. In order to be adopted, the foot must cost less than $10 USD, be mass-manufacturable, and meet or exceed the performance of the Jaipur Foot, BMVSS' current prosthetic foot. This thesis investigates different metrics that are used to design and evaluate prosthetic feet and presents an analysis and evaluation of a solid ankle, cantilever beam - type prosthetic foot. Methods of comparing prosthetic feet in industry and in academia are discussed using a review of literature. These comparisons can be categorized into mechanical, metabolic, subjective, and gait analysis comparisons. The mechanical parameters are the most useful for designing a new prosthetic foot, as they are readily translated into engineering design requirements; however, these are the furthest removed from the performance of the foot. On the other end of the spectrum are metabolic and subjective parameters, which are useful in evaluating prosthetic feet because the objectives of minimizing energy expenditure and earning user approval are clear. Somewhere between these is gait analysis. The literature review reveals that not enough information is available to bridge these categories, that is, there is no consensus on how any particular mechanical parameter affects the subjective ranking of a prosthetic foot. Two mechanical parameters emerge as necessary, but not sufficient: the rollover shape and the energy storage and return capacity of a prosthetic foot. A simple model of a solid ankle, cantilever beam - type prosthetic foot is analyzed in the context of these two parameters. By applying beam bending theory and published gait analysis data, it is found that an unconstrained cantilever beam maximizes energy storage and return, but does not replicate a physiological roll-over shape well regardless of bending stiffness. Finite element analysis is used to find the roll-over shape and energy storage capacity from the same model when a mechanical constraint is added to prevent over deflection. The results show that for very compliant beams, the roll-over shape is nearly identical to the physiological rollover shape, but the energy storage capacity is low. For stiff beams, the opposite is true. Thus there is a trade-off between roll-over shape and energy storage capacity for cantilever beam type feet that fit this model. Further information is required to determine the relative importance of each of these parameters before an optimal bending stiffness can be found. A proof-of-concept prototype was built according to this model and tested in India at BMVSS. It was found that another parameter - perception of stability, which is perhaps dependent on the rate of forward progression of the center of pressure is equally important as, if not more than, the other parameters investigated here. Perception of stability increased with bending stiffness. The prototype foot received mixed feedback and has potential to be further refined. However, the solid ankle model is inappropriate for persons living in India, as it does not allow enough true dorsiflexion to permit squatting, an important activity that is done many times a day in the target demographic. Future work will use a similar method to design and optimize a prosthetic foot with a rotational ankle joint to allow this motion.

Download or read book Progress in Prosthetics written by Bess Furman and published by . This book was released on 1962 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effect of Prosthetic Foot Component Stiffness on Initiation and Termination of Transtibial Amputee Gait written by Travis J. Peterson and published by . This book was released on 2012 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: \Lower limb loss is an increasingly common clinical problem in our society. Along with the loss of limb, amputees must also learn to use their new prosthetic device for their daily activities. The ideal stiffness characteristics of prosthetic feet for different functional activities may vary depending on each activity. Therefore the prescribed foot must be a compromise of multiple ideals out of functional necessity. Quantification of gait and stability characteristics is necessary to provide vital information into the design and prescription of future prosthetics to align with prosthetic users' needs and activity profiles. The purpose of this study was to determine the effects of varying component stiffness of the prosthetic foot on locomotion and stability measures during gait initiation and termination. It was hypothesized that the leading sound condition would display greater excursions than the leading prosthetic condition for both mediolateral and anteroposterior excursions of the center of mass and center of pressure. It was also hypothesized that there would be differences between compliant and stiff heel components in each excursion measure. Six male unilateral transtibial amputees participated in this study (41 ± 13.7 years, 1.82 ± 0.06 m, and 85.8 ± 15.5 kg). Subjects completed gait initiation and termination trials while force plates recorded ground reaction forces and motion capture was used to measure body kinematics. Center of mass (COM) and center of pressure (COP) measures were derived from the data gathered. The originally captured data were filtered to obtain a clear signal to noise ratio. Specific gait events from the analysis provided consistent intervals to measure center of mass and center of pressure excursions in the two gait activities studied. Results indicated that leading with the sound limb during initiation and termination increased the COM excursion in the anteroposterior direction. A lack of significant results in the COP and all M/L directions between leading foot conditions indicates there are multiple strategies to achieve initiation and termination. A reliance on the sound limb agrees with previous studies, and appears to be functionally necessary to transtibial amputee gait. However, prosthetic foot stiffness levels have varied effects and should be taken into account for the design and prescription of future prosthetic feet.

Download or read book The Mechanical Response and Parametric Optimization of Ankle foot Devices written by Kevin Christopher Smith and published by . This book was released on 2016 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: To improve the mobility of lower limb amputees, many modern prosthetic ankle-foot devices utilize a so called energy storing and return (ESAR) design. This allows for elastically stored energy to be returned to the gait cycle as forward propulsion. While ESAR type feet have been well accepted by the prosthetic community, the design and selection of a prosthetic device for a specific individual is often based on clinical feedback rather than engineering design. This is due to an incomplete understanding of the role of prosthetic design characteristics (e.g. stiffness, roll-over shape, etc.) have on the gait pattern of an individual. Therefore, the focus of this work has been to establish a better understanding of the design characteristics of existing prosthetic devices through mechanical testing and the development of a prototype prosthetic foot that has been numerically optimized for a specific gait pattern. The component stiffness, viscous properties, and energy return of commonly prescribed carbon fiber ESAR type feet were evaluated through compression testing with digital image correlation at select loading angles following the idealized gait from the ISO 22675 standard for fatigue testing. A representative model was developed to predict the stress within each of the tested components during loading and to optimize the design for a target loading response through parametric finite element analysis. This design optimization approach, along with rapid prototyping technologies, will allow clinicians to better identify the role the design characteristics of the foot have on an amputee's biomechanics during future gait analysis.

Download or read book Design and Testing of an Ankle foot Prosthesis and a Hip Exoskeleton to Improve Balance related Outcomes and Prevent Falls written by Vincent Louie Chiu and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Falling is a serious issue that affects millions of people, including people with lower limb amputation and older adults. Falls can lead to serious injury or death, and even the fear of falling results in restrictions on mobility and reductions in quality of life. Assistive devices could address this need by augmenting the three primary strategies humans use to maintain balance: applying ankle torque to modulate center of pressure and pushoff work, using hip torque to change center of mass position and velocity, and placing the foot to alter base of support. In my doctoral research, I have designed and tested devices intended to assist people with these three balance strategies. First, I designed a prosthetic foot with actuation in the frontal and sagittal planes, which is capable of modulating the center of pressure between the foot and the ground. I then used this foot to test the biomechanical effects of a prosthesis controller designed to mitigate the effects of uneven terrain. Finally, I designed a bilateral hip exoskeleton with actuation in the frontal and sagittal planes, which can be used to modulate hip torques and assist with foot placement. These projects have led to a better understanding of the relative efficacy of different balance enhancement techniques and have yielded new experimental tools for future studies of fall prevention.