Evaluation of the accuracy of a UWB tracker for in-home positioning for older adults.

The population of older adults is rapidly growing. In-home monitoring systems have been used to support aging-in-place. Ambient sensors or wearable localizers can be used but may be too low resolution, while camera systems are invasive to privacy. Ultra-wideband (UWB) localization offers precise positioning by placing anchors throughout the house and wearing a tag that is tracked by the anchors. In this study, the accuracy of UWB for indoor tracking was evaluated in a motion capture gait lab and in a mock condo in the Glenrose Rehabilitation Hospital. First, the configuration of UWB was tested, changing factors related to sampling time, anchor placement and line-of-sight. Comparing these factors to the configurations recommended by the manufacturer guidelines, accuracies remained within 14 cm. We then performed static and dynamic accuracy tests, with dynamic testing comprised of rolling and walking motions. In the motion capture lab, we found localization accuracies of 7.0 ± 11.1 cm while in the mock condo, we found accuracies of 27.3 ± 12.9 cm. Dynamic testing with rolling motions had an average of 19.1 ± 1.6 cm while walking was 20.5 ± 4.2 cm. The mean accuracy of UWB is within the 30 cm target for indoor localization.

Differences in angular kinematics when using thigh, implant, or medial knee markers in osseointegrated transfemoral prosthetic gait.

BACKGROUND: The Helen Hayes anatomical model is commonly used in clinical gait analysis with standard medial/lateral knee and thigh markers. METHODS: To quantify soft-tissue artifacts associated with the thigh marker following osseointegration surgery, we added an "implant marker" on the implant extending from the femur, with the objective of identifying the differences in the angular kinematics when using the standard versus implant marker. One female adult with an osseointegrated transfemoral prosthesis walked overground for three trials, and common kinematic measures were calculated from motion capture data. FINDINGS: The results indicated that, when using the thigh marker, a peak of knee varus occurred during the swing phase on the prosthetic side, which is unusual during gait and not feasible for hinge joint prostheses. When using the implant marker, knee varus/valgus was closer to normative. Using the thigh marker, the results showed an internal hip rotation at the start of stance and during the mid and terminal swing phases. In contrast, external hip rotation occurred in both stance and swing phases using the implant marker. Moreover, when selecting the medial knee marker instead of the thigh marker, the angular kinematics and range of motion of knee varus/valgus and hip rotation were comparable to those for the implant marker. INTERPRETATION: This finding suggests that when studying osseointegration gait, using an implant marker will result in more accurate femoral and knee joint motion than using the thigh marker. Changing the selection of markers can reduce the errors of knee varus/valgus and hip kinematics in osseointegrated transfemoral prosthetic gait.

Functional characterization of plantar pressure patterns in gait of typically developing children using dynamic pedobarography.

BACKGROUND: Abnormal foot posture is a common complaint presented in pediatric and pediatric orthopedic clinics. Functional, objective assessment of foot posture, with the potential for early identification of pathologic foot deformities, has, however, been lacking to date. While quantifying functional and regional impulses via dynamic pedobarography can improve the clinical assessment of children's feet, normative values have not yet been reported or characterized. RESEARCH QUESTION: The objectives of this study were to: (1) quantify and characterize the pattern and spectrum of foot impulses in walking-aged, typically developing children; and (2) compare these to impulses from non-disabled adults. METHODS: Foot impulses of 102 participants (52 female) in five pre-determined age groups (2-3, 4-6, 7-10, 11-14, 15-17 years) were examined using dynamic pedobarography. Each pressure map (3 per foot per child) was divided according to anatomical foot regions: the hallux, heel, medial forefoot, lateral forefoot, lesser toes (D2 to D5), and midfoot. The impulse was calculated for each region and used to generate regional percent impulses and impulse ratios to assess anteroposterior and mediolateral balance within the foot. RESULTS: The impulse through the midfoot was highest in the youngest age group, with a corresponding lower impulse through the medial forefoot. As age advanced, the midfoot impulse decreased (p = 0.001), and the forefoot balance shifted slightly more medially (%Medial Forefoot: p = 0.004; Medial-Lateral Forefoot Balance: p = 0.019). When compared to adults, there were no significant differences between 15-17 year old children and adults in any of the regional percent impulses and impulse ratios. This indicates that skeletal maturity of the foot by late adolescence results in functional characteristics seen in adults. SIGNIFICANCE: The age-standardized norms of functional and regional impulse measures in children reported in this study can be used as a comparative benchmark in the clinical assessment of children presenting with various foot deformities.

Spatial and temporal relation of kinematics and muscle activity during unstable sitting.

Recent work suggests that kinematics-based electrical stimulation may restore dynamic trunk stability following spinal cord injury. However, to ensure fatigue-resistant control, knowledge of the relation between body motion and the activity of relevant muscles during non-impaired, unstable sitting may be beneficial. Therefore, our objective was to quantify the spatial and temporal relationships between (1) characteristic angular kinematics (i.e., the kinematics characterizing trunk stabilization) and (2) trunk and upper leg muscle activity in unstable sitting as elicited via a wobble board. Wobble board motion and bilateral electromyograms from fourteen trunk and upper leg muscles were recorded in fifteen non-disabled participants (i.e., individuals with no history of neurological or musculoskeletal impairments or pain, gait or balance difficulties, or use of a walking aid) sitting on a wobble board. The relationship between wobble board tilt and the electromyograms was quantified using cross-correlation analysis. During unstable sitting, the trunk was stabilized through direction-specific activation of the trunk and upper leg muscles, preceding wobble board displacement by 110-230 ms. Direction-specific activation implies the presence of active neural control, while preceding activation may be needed to account for known torque generation time delays. Furthermore, the specific muscles activated for each direction of wobble board displacement suggest the use of stiffness control in the anterior-posterior, but not medial-lateral direction. Future work will use the gained insights in defining the muscle stimulation patterns of kinematics-based neuroprostheses that can restore trunk stability following impairment.

Contributions of Voice and Nonverbal Communication to Perceived Masculinity-Femininity for Cisgender and Transgender Communicators.

Purpose The purpose of this study was twofold: (a) to identify a set of communication-based predictors (including both acoustic and gestural variables) of masculinity-femininity ratings and (b) to explore differences in ratings between audio and audiovisual presentation modes for transgender and cisgender communicators. Method The voices and gestures of a group of cisgender men and women (n = 10 of each) and transgender women (n = 20) communicators were recorded while they recounted the story of a cartoon using acoustic and motion capture recording systems. A total of 17 acoustic and gestural variables were measured from these recordings. A group of observers (n = 20) rated each communicator's masculinity-femininity based on 30- to 45-s samples of the cartoon description presented in three modes: audio, visual, and audio visual. Visual and audiovisual stimuli contained point light displays standardized for size. Ratings were made using a direct magnitude estimation scale without modulus. Communication-based predictors of masculinity-femininity ratings were identified using multiple regression, and analysis of variance was used to determine the effect of presentation mode on perceptual ratings. Results Fundamental frequency, average vowel formant, and sound pressure level were identified as significant predictors of masculinity-femininity ratings for these communicators. Communicators were rated significantly more feminine in the audio than the audiovisual mode and unreliably in the visual-only mode. Conclusions Both study purposes were met. Results support continued emphasis on fundamental frequency and vocal tract resonance in voice and communication modification training with transgender individuals and provide evidence for the potential benefit of modifying sound pressure level, especially when a masculine presentation is desired.

Validity of using wearable inertial sensors for assessing the dynamics of standing balance.

Observational balance tests (e.g., Berg Balance Scale) are used to evaluate fall-risk. However, they tend to be subjective, and their reliability and sensitivity can be limited. The use of in-lab equipment for objective balance evaluation has not been common in clinical practice, due to the requirement of an equipped lab space. While inertial measurement units (IMUs) enable objective out-of-lab balance assessment, their accuracy has not been validated. This study aims to investigate the accuracy of IMUs against in-lab equipment for characterizing standing balance. Ten non-disabled individuals participated in a two-minute standing test on a force-plate. Four approaches were used for estimating inter-segmental moments and center of pressure (COP) position in a four-segment model: (1) camera-based bottom-up approach; (2) camera-based top-down approach; (3) IMU-based (accelerometer) top-down approach; and (4) IMU-based (accelerometer and gyroscope) top-down approach. Approaches 2 to 4 resulted in high accuracy compared to the reference, Approach 1. The root-mean-square errors in estimating the segments' orientation, ground reaction forces, COP position, and joint moments were smaller than 0.3°, 0.2 N/kg, 1.5 mm, and 0.016N·m/kg, respectively. Since no significant differences were observed between the accuracy of Approaches 3 and 4, only accelerometer recordings are needed and could be recommended for monitoring standing balance.

Functional, impulse-based quantification of plantar pressure patterns in typical adult gait.

BACKGROUND: Dynamic pedobarography is used to measure the change in plantar pressure distribution during gait. Clinical methods of pedobarographic analysis lack, however, a standardized, functional segmentation or require costly motion capture technology and expertise. Furthermore, while commonly used pedobarographic measures are mostly based on peak pressures, progressive foot deformities also depend on the duration the pressure is applied, which can be quantified via impulse measures. RESEARCH QUESTION: Our objectives were to: (1) develop a standardized method for functionally segmenting pedobarographic data during gait without the need for motion capture; (2) compute pedobarographic measures that are based on each segment's vertical impulse; and (3) obtain a normative set of such pedobarographic measures for non-disabled gait. METHODS: Pedobarographic data was collected during gait from sixty adults with normal feet. Using the maximum pressure map for each trial, an expert and novice rater independently identified the hallux, heel, medial forefoot, and lateral forefoot and computed nine normalized vertical impulse measures. RESULTS: From the computed impulse measures, the Heel-to-Forefoot Balance was 33.3 ± 5.5%, the Medial-Lateral Forefoot Balance (with hallux) 59.2 ± 8.0%, the Medial-Lateral Forefoot Balance (without hallux) 53.5 ± 7.7%, and the Hallux-to-Medial Forefoot Balance 21.0 ± 8.9% (mean ± standard deviation). The intra- and inter-rater reliability ranged between 0.93 and 1.00 and between 0.89 and 0.99, respectively (ICC(2,1)). SIGNIFICANCE: We developed a simple, stand-alone method for pedobarographic segmentation that is mechanistically linked to relevant anatomical regions of the foot. The normative impulse measures exhibited excellent reliability. This normative dataset is currently used in the clinical assessment of different foot deformities and gait impairments, and in the evaluation of treatment outcomes.

The utility of normative foot floor angle data in assessing toe-walking.

Initial heel contact is an important attribute of gait, and failure to complete the heel rocker reduces gait stability. One common goal in treating toe-walking is to restore heel strike and prevent or reduce early heel rise. Foot floor angle (FFA) is a measure of toe-walking that is valuable for quantifying foot orientation at initial contact when using ankle dorsiflexion angle alone is misleading. However, no age-standardized FFA norms exist for clinical evaluation. Our objectives were to: (1) obtain normative FFA in typically developing children; and (2) examine its utility in the example of toe-walking secondary to unilateral cerebral palsy. Gait kinematics were acquired and FFA trajectories computed for 80 typically developing children (4-18 years). They were also obtained retrospectively from 11 children with toe-walking secondary to unilateral cerebral palsy (4-10 years), before and after operative intervention, and compared to 40 age-matched, typically developing children. FFA at initial contact was significantly different (P<.001) between pre-surgery toe-walking (-14.7±9.7°; mean±standard deviation) and typical gait (18.7±2.8°). Following operative lengthening of the gastrocnemius-soleus complex on the affected side, FFA at initial contact (-0.9±5.3°) was significantly improved (P<.001). Furthermore, several cases were identified for which the sole use of ankle dorsiflexion angle to capture toe-walking is misleading. The assessment of FFA is a simple method for providing valuable quantitative information to clinicians regarding foot orientation during gait. The demonstrated limitations of using ankle dorsiflexion angle alone to estimate foot orientation further emphasize the utility of FFA in assessing toe-walking.

Normative data for modified Box and Blocks test measuring upper-limb function via motion capture.

Motion analysis is an important tool for examining upper-limb function. Based on previous work demonstrating a modified Box and Blocks (BB) test with motion capture to assess prosthetic performance, we collected data in 16 nondisabled participants to establish normative kinematics for this test. Four motions of the modified BB test were analyzed to establish kinematic data for upper-limb and trunk motion. The test was repeated for right and left arms in standing and seated positions. Data were compared using a nonparametric Friedman test. No differences were found between right- and left-hand performance other than for task completion time. Small but significant differences were found for standing and seated performance, with slightly greater ranges in standing for axial trunk rotation, medial-lateral sternum displacement, and anterior-posterior hand displacement. The kinematic trajectories, however, were very consistent. The consistency in our nondisabled data suggests that normative kinematic trajectories can be defined for this task. This motion capture procedure may add to the understanding of movement in upper-limb impairment and may be useful for measuring the effect of interventions to improve upper-limb function.

Leg dominance may not be a predictor of asymmetry in peak joint moments and ground reaction forces during sit-to-stand movements.

Sit-to-stand transfer is a common prerequisite for many daily tasks. Literature often assumes symmetric behavior across the left and right side. Although this assumption of bilateral symmetry is prominent, few studies have validated this supposition. This pilot study uniquely quantifies peak joint moments and ground reaction forces (GRFs), using a Euclidian norm approach, to evaluate bilateral symmetry and its relation to lower limb motor-dominance during sit to stand in ten healthy males. Peak joint moments and GRFs were determined using a motion capture system and inverse dynamics. This analysis included joint moment contributions from all three body planes (sagittal, coronal, and axial) as well as vertical and shearing GRFs. A paired, one-tailed t test was used, suggesting asymmetrical joint moment development in all three lower extremity joints as well as GRFs (P < .05). Furthermore, using an unpaired two-tailed t test, asymmetry developed during these movements does not appear to be predictable by participants' lower limb motor-dominance (P < .025). Consequently, when evaluating sit-to-stand it is suggested the effects of asymmetry be considered in the interpretation of data. The absence of a relationship between dominance and asymmetry prevents the suggestion that one side can be tested to infer behavior of the contralateral.

Characterizing asymmetry across the whole sit to stand movement in healthy participants.

Sit-to-stand transfer (STS) is a common yet critical prerequisite for many daily tasks. Literature conducted on healthy STS often assume the body to behave symmetrically across the left and right side; yet only a few studies have been conducted to investigate this supposition. These studies have focused on a single numerical indicator such as peak joint moment (JM) values to describe symmetricity; however, STS is a dynamic and time dependent movement. This study addresses the validity of peak value analyses through the introduction of a time based peak-offset measure and proposes two time-dependent techniques to further characterize asymmetry and assesses their feasibility in ten (10) healthy male participants. JM and joint power (JP) over the whole STS movement was determined using motion capture and inverse dynamics. Using a paired one-tailed t-test differences were found in the time at which the left and right side reached peak values in all lower extremity joints (p<0.05) with exception of the hip JM. Using a measure of JM and JP straight-difference it was determined that the ankle joint displayed the largest number of JM and JP development strategies of all the lower extremity joints. Finally, through numerical integration of the JM and JP data with respect to time, it was found that the longer one side spends dominating the movement, the larger the excess angular impulse and work that can be expected from that side. The results suggest that when analyzing STS movements, one must be aware of the potential asymmetry present even in healthy movements. Furthermore, a simple peak JM or JP analysis may not fully describe the extent of these asymmetries.

Case report of modified Box and Blocks test with motion capture to measure prosthetic function.

This case study report demonstrates the use of motion analysis with a modification of the Box and Blocks test. The goal was to quantify observed improvements in compensatory movements and simultaneous control in a subject using different prostheses before and after targeted muscle reinnervation (TMR) surgery. This is a single case study with data collection using a body-powered prosthesis pre-TMR surgery and 6 mo postfitting with a TMR myoelectric prosthesis. The Box and Blocks test was modified for cyclical motion within a motion capture laboratory. With the TMR myoelectric prosthesis, the subject was able to simultaneously activate the hand and elbow. Task performance was slower, but there was improved elbow flexion and less trunk compensatory motion than with the body-powered prosthesis. There are several limitations to the case study because there is no direct comparison of myoelectric performance before and after TMR surgery; however, the current report presents a potential method to quantify quality of motion and compensatory movements of prosthetic users. With further study, this test procedure has the potential to be a useful outcome measure for future standardized assessments of upper-limb prosthetic function.