Deborah D. Espy

Inoculation Against Falls: Rapid Adaptation by Young and Older Adults to Slips During Daily Activities

OBJECTIVE To determine whether aging diminishes ones ability to rapidly learn to resist falls on repeated-slip exposure across different activities of daily living. DESIGN Quasi-experimental controlled trial. SETTING Two university-based research laboratories. PARTICIPANTS Young (n=35) and older (n=38) adults underwent slips during walking. Young (n=60) and older (n=41) adults underwent slips during a sit-to-stand task. All (N=174) were healthy and community dwelling. INTERVENTION Low-friction platforms induced unannounced blocks of 2 to 8 repeated slips interspersed with blocks of 3 to 5 nonslip trials during the designated task. MAIN OUTCOME MEASURES The incidence of falls and balance loss. Dynamic stability (based on center of mass position and velocity) and limb support (based on hip height) 300 ms after slip onset. RESULTS Under strictly controlled, identical low-friction conditions, all participants experienced balance loss, but older adults were over twice as likely as young to fall on the first, unannounced, novel slip in both tasks. Independent of age or task, participants adapted to avoid falls and balance loss, with most adaptation occurring in early trials. By the fifth slip, the incidence of falls and balance loss was less than 5% and 15%, respectively, regardless of age or task. Reductions in falls and balance loss for each task were accomplished through improved control of stability and limb support in both age groups. A rapidly reversible age- and task-dependent waning of motor learning occurred after a block of nonslip trials. Adaptation to walk slips reached a steady state in the second slip block regardless of age. CONCLUSIONS The ability to rapidly acquire fall-resisting skills on repeated-slip exposure remains largely intact at older ages and across functional activities. Thus, repeated-slip exposure might be broadly effective in inoculating older adults against falls.

Dynamic gait stability, clinical correlates, and prognosis of falls among community-dwelling older adults

OBJECTIVE To establish an accurate measure for prognostic assessment of fall risk in community-dwelling older adults, this study examined the prediction accuracy of a dynamic gait stability measure and common clinical tests for slip-related falls among these adults. DESIGN Participants were tested for their fall-risk likelihood on a slip-test. SETTING Biomechanics research laboratory. PARTICIPANTS Community-dwelling older adults (N=119; ≥65y). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Participants performed a battery of clinical tests, including Berg Balance Scale, Timed Up & Go (TUG) test, static posturography, isometric muscle strength, and bone density. They were then exposed to an unannounced slip during gait. The dynamic stability during unperturbed gait was measured based on the center of mass position and velocity relative to the limits of stability against backward falling. Accuracy of each measure was examined for prediction of slip outcome (fall or recovery). RESULTS On the slip, 59 participants fell, 56 recovered their balance, and 4 were harness-assisted. Dynamic stability predicted fall outcome with 69% accuracy. Except for TUG and bone density, no other measure could differentiate fallers from nonfallers; TUG predicted 56% of fall outcomes. CONCLUSIONS Reproduction of actual falls provides a new benchmark for evaluating the prognostic power of different performance-based assessment tools. The TUG was able to better predict fall outcome than other clinical measures; however, the new dynamic gait stability measure was more sensitive than TUG in its prediction of falls. Ultrasound bone scan could be used to screen older adults for fall risk.

Realtime Motion Assessment For Rehabilitation Exercises: Integration Of Kinematic Modeling With Fuzzy Inference

Abstract This article describes a novel approach to realtime motion assessment for rehabilitation exercises based on the integration of comprehensive kinematic modeling with fuzzy inference. To facilitate the assessment of all important aspects of a rehabilitation exercise, a kinematic model is developed to capture the essential requirements for static poses, dynamic movements, as well as the invariance that must be observed during an exercise. The kinematic model is expressed in terms of a set of kinematic rules. During the actual execution of a rehabilitation exercise, the similarity between the measured motion data and the model is computed in terms of their distances, which are then used as inputs to a fuzzy interference system to derive the overall quality of the execution. The integrated approach provides both a detailed categorical assessment of the overall execution of the exercise and the degree of adherence to individual kinematic rules.

A Kinect-based rehabilitation exercise monitoring and guidance system

In this paper, we describe the design and implementation of a Kinect-based system for rehabilitation exercises monitoring and guidance. We choose to use the Unity framework to implement our system because it enables us to use virtual reality techniques to demonstrate detailed movements to the patient, and to facilitate examination of the quality and quantity of the patient sessions by the clinician. The avatar-based rendering of motion also preserves the privacy of the patients, which is essential for healthcare systems. The key contribution of our research is a rule-based approach to realtime exercise quality assessment and feedback. We developed a set of basic rule elements that can be used to express the correctness rules for common rehabilitation exercises.

A feasibility study of using a single Kinect sensor for rehabilitation exercises monitoring: A rule based approach

In this paper, we present a feasibility study for using a single Microsoft Kinect sensor to assess the quality of rehabilitation exercises. Unlike competing studies that have focused on the validation of the accuracy of Kinect motion sensing data at the level of joint positions, joint angles, and displacement of joints, we take a rule based approach. The advantage of our approach is that it provides a concrete context for judging the feasibility of using a single Kinect sensor for rehabilitation exercise monitoring. Our study aims to answer the following question: if it is found that Kinects measurement on a metric deviates from the ground truth by some amount, is this an acceptable error? By defining a set of correctness rules for each exercise, the question will be answered definitively with no ambiguity. Defining appropriate context in a validation study is especially important because (1) the deviation of Kinect measurement from the ground truth varies significantly for different exercises, even for the same joint, and (2) different exercises have different tolerance levels for the movement restrictions of body segments. In this study, we also show that large but systematic deviations of the Kinect measurement from the ground truth are not as harmful as it seems because the problem can be overcome by adjusting parameters in the correctness rules.

Rule based realtime motion assessment for rehabilitation exercises

In this paper, we describe a rule based approach to realtime motion assessment of rehabilitation exercises. We use three types of rules to define each exercise: (1) dynamic rules, with each rule specifying a sequence of monotonic segments of the moving joint or body segment, (2) static rules for stationary joints or body segments, and (3) invariance rules that dictate the requirements of moving joints or body segments. A finite state machine based approach is used in dynamic rule specification and realtime assessment. In addition to the typical advantages of the rule based approach, such as realtime motion assessment with specific feedback, our approach has the following advantages: (1) increased reusability of the defined rules as well as the rule assessment engine facilitated by a set of generic rule elements; (2) increased customizability of the rules for each exercise enabled by the use of a set of generic rule elements and the use of extensible rule encoding method; and (3) increased robustness without relying on expensive statistical algorithms to tolerate motion sensing errors and subtle patient errors.

“Kinect-ing” With Clinicians: A Knowledge Translation Resource to Support Decision Making About Video Game Use in Rehabilitation

Microsofts Kinect for Xbox 360 virtual reality (VR) video games are promising rehabilitation options because they involve motivating, full-body movement practice. However, these games were designed for recreational use, which creates challenges for clinical implementation. Busy clinicians require decision-making support to inform game selection and implementation that address individual therapeutic goals. This article describes the development and preliminary evaluation of a knowledge translation (KT) resource to support clinical decision making about selection and use of Kinect games in physical therapy. The knowledge-to-action framework guided the development of the Kinecting With Clinicians (KWiC) resource. Five physical therapists with VR and video game expertise analyzed the Kinect Adventure games. A consensus-building method was used to arrive at categories to organize clinically relevant attributes guiding game selection and game play. The process and results of an exploratory usability evaluation of the KWiC resource by clinicians through interviews and focus groups at 4 clinical sites is described. Subsequent steps in the evaluation and KT process are proposed, including making the KWiC resource Web-based and evaluating the utility of the online resource in clinical practice.

Feasible Stability Region in the Frontal Plane During Human Gait

The inability to adequately control the motion of the center of mass (COM) in the frontal plane may result in a loss of balance causing a sideways fall during human gait. The primary purposes of this study were (1) to derive the feasible stability region (FSR) in the mediolateral direction, and (2) to compare the FSR with the COM motion state taken from 193 trials among 39 young subjects at liftoff during walking at different speeds. The lower boundary of the FSR was derived, at a given initial COM location, as the minimum rightward COM velocity, at liftoff of the left foot, required to bring the COM into the base of support (BOS), i.e., the right (stance) foot, as the COM velocity diminishes. The upper boundary was derived as the maximum rightward COM velocity, beyond which the left foot must land to the right of the right foot (BOS) in order to prevent a fall. We established a 2-link human model and employed dynamic optimization to estimate these threshold values for velocity. For a range of initial COM positions, simulated annealing algorithm was used to search for the threshold velocity values. Our study quantified the extent to which mediolateral balance can still be maintained without resorting to a crossover step (the left foot lands to the right of the BOS) for balance recovery. The derived FSR is in good agreement with our gait experimental results.

LiftingDoneRight: A Privacy-Aware Human Motion Tracking System for Healthcare Professionals

This article describes the design and implementation of LiftingDoneRight, a novel system for healthcare professionals to enhance their compliance with best practices and regulations regarding proper body mechanics for lifting and pulling activities. The system uses Microsoft Kinect to track the motion of consented users non-intrusively. The system relies on the use of a smartwatch to deliver an alert via vibration and text display whenever a wrong activity that violated the proper body mechanics has been detected. A core contribution of this study is a registration mechanism for a healthcare professional to explicitly give permission to the system to monitor his or her activities. Furthermore, a non-intrusive biometrics-based single sign-on mechanism is incorporated into the system to allow a user to be automatically identified for tracking as long as the user has manually registered with the system before. Finally, the system offers a number of configurations to accommodate different usability needs and privacy requirements.