Characterizing upper extremity kinematics in typically developing children during box and blocks test.

Upper extremity kinematics are important for understanding functional ability and performance improvements. The Box and Blocks test (BBT) is a standardized functional test used to measure manual dexterity when evaluating children or patients following a stroke. The BBT measures the number of blocks moved in one minute and therefore, kinematic measures and compensatory strategies cannot be assessed. This study examined the correlation between upper extremity kinematics and cycle time per block movement during the BBT in three age groups (7-, 9-, and 11-year-olds). Participants completed one BBT session while test scores and kinematic measures (hand velocity and position and shoulder, elbow, and wrist range of motion and peak joint angles) were captured using standard three-dimensional motion capture techniques. Kinematic measures were determined for block movements during the middle of each BBT trial. A mixed-effects model was used to identify group differences (α = 0.05). BBT score was different (p = 0.005) between the 7- (44.88 ± 6.03) and the 11-year-old age group (56.95 ± 8.37) along with peak shoulder flexion (p = 0.024) and abduction (p = 0.022). Peak elbow flexion was different (p = 0.049) between the 9- and 11-year-old age groups. No differences were seen between the 7- and 9-year-old age groups. Pearson's Correlation Coefficients were determined between cycle time and each significant kinematic measure, where the cycle time is specific to each block movement (BBT score) and is correlated to the BBT score. This resulted in weak correlations for all the comparisons. Therefore, using BBT score alone is not representative of UE kinematics and both should be collected during this task to provide insight into movement mechanics in a pediatric population.

Approximate Bayesian Techniques for Statistical Model Selection and Quantifying Model Uncertainty-Application to a Gait Study.

Frequently, biomedical researchers need to choose between multiple candidate statistical models. Several techniques exist to facilitate statistical model selection including adjusted R2, hypothesis testing and p-values, and information criteria among others. One particularly useful approach that has been slow to permeate the biomedical literature is the notion of posterior model probabilities. A major advantage of posterior model probabilities is that they quantify uncertainty in model selection by providing a direct, probabilistic comparison among competing models as to which is the "true" model that generated the observed data. Additionally, posterior model probabilities can be used to compute posterior inclusion probabilities which quantify the probability that individual predictors in a model are associated with the outcome in the context of all models considered given the observed data. Posterior model probabilities are typically derived from Bayesian statistical approaches which require specialized training to implement, but in this paper we describe an easy-to-compute version of posterior model probabilities and inclusion probabilities that rely on the readily-available Bayesian information criterion. We illustrate the utility of posterior model probabilities and inclusion probabilities by re-analyzing data from a published gait study investigating factors that predict required coefficient of friction between the shoe sole and floor while walking.

A new method for assessing landing kinematics in non-laboratory settings.

OBJECTIVES: 1) Determine the concurrent validity of using automated 2D video analysis relative to 3D motion capture for assessing frontal and sagittal-plane knee kinematics during landing, 2) compare the accuracy of visually estimating joint center locations (2D Manual) with computing joint center locations using anatomical markers (2D Automatic), and 3) compare landing kinematics between a controlled laboratory setting and a non-laboratory setting. DESIGN: Validity/repeatability study. SETTINGS: Biomechanics research laboratory and non-laboratory athletic facility. PARTICIPANTS: Thirty uninjured recreational athletes. MAIN OUTCOME MEASURES: Peak knee flexion, knee flexion range of motion, peak knee frontal plane projection angle, and knee frontal plane projection angle range of motion during bilateral and unilateral landing were measured simultaneously in 3D using motion capture and in 2D using two low-cost video cameras during the first study session (biomechanics research laboratory), and in 2D only during the second study session (non-laboratory athletic facility). RESULTS: There was good to excellent agreement between 3D motion capture and both 2D Manual (ICC = 0.86-0.99) and 2D Automatic (ICC = 0.89-0.99) video analysis methods. There was good to excellent agreement between data collected in a laboratory and non-laboratory setting (ICC = 0.75-0.95). CONCLUSION: The methods introduced in this study are inexpensive, reliable, and feasible for use in non-laboratory settings.

Web Conferencing Facilitation Within Problem-Based Learning Biomedical Engineering Courses.

Problem-based learning (PBL) has been effectively used within BME education, though there are several challenges in its implementation within courses with larger enrollments. Furthermore, the sudden transition to online learning from the COVID-19 pandemic introduced additional challenges in creating a similar PBL experience in an online environment. Online constrained PBL was implemented through asynchronous modules and synchronous web conferencing with rotating facilitators. Overall, facilitators perceived web conferencing facilitation to be similar to in-person, but noted that students were more easily "hidden" or distracted. Students did not comment on web conferencing facilitation specifically, but indicated the transition to online PBL was smooth. Course instructors identified that a fully synchronous delivery as well as modifications of Group Meeting Minutes assignments as potential modifications for future offerings. Future work will aim to address the perceptions and effectiveness of web conferencing facilitation for PBL courses within an undergraduate BME curriculum, as web conferencing could prove to be another significant breakthrough in addressing challenges of problem-based learning courses.

Required friction during overground walking is lower among obese compared to non-obese older men, but does not differ with obesity among women.

Obesity and aging have been independently associated with altered required friction during walking, but it is unclear how these factors interact to influence the likelihood of slipping. Therefore, the purpose of this study was to determine whether there are differences related to obesity and aging on required friction during overground walking. Fourteen older non-obese, 11 older obese, 20 younger non-obese, and 20 younger obese adults completed walking trials at both a self-selected and hurried speed. When walking at a hurried speed, older obese men walked at a slower gait speed and exhibited lower frictional demands compared both to older non-obese men and to younger obese men. No differences in required friction were found between non-obese and obese younger adults. These results suggest that the increased rate of falls among obese or older adults is not likely due to a higher risk of slip initiation.

An evaluation of irreversible electroporation thresholds in human prostate cancer and potential correlations to physiological measurements.

Irreversible electroporation (IRE) is an emerging cancer treatment that utilizes non-thermal electric pulses for tumor ablation. The pulses are delivered through minimally invasive needle electrodes inserted into the target tissue and lead to cell death through the creation of nanoscale membrane defects. IRE has been shown to be safe and effective when performed on tumors in the brain, liver, kidneys, pancreas, and prostate that are located near critical blood vessels and nerves. Accurate treatment planning and prediction of the ablation volume require a priori knowledge of the tissue-specific electric field threshold for cell death. This study addresses the challenge of defining an electric field threshold for human prostate cancer tissue. Three-dimensional reconstructions of the ablation volumes were created from one week post-treatment magnetic resonance imaging (MRIs) of ten patients who completed a clinical trial. The ablation volumes were incorporated into a finite element modeling software that was used to simulate patient-specific treatments, and the electric field threshold was calculated by matching the ablation volume to the field contour encompassing the equivalent volume. Solutions were obtained for static tissue electrical properties and dynamic properties that accounted for electroporation. According to the dynamic model, the electric field threshold was 506 ± 66 V/cm. Additionally, a potentially strong correlation (r = -0.624) was discovered between the electric field threshold and pre-treatment prostate-specific antigen levels, which needs to be validated in higher enrollment studies. Taken together, these findings can be used to guide the development of future IRE protocols.

A Comparison of Body Segment Inertial Parameter Estimation Methods and Joint Moment and Power Calculations During a Drop Vertical Jump in Collegiate Female Soccer Players.

Athletic individuals may differ in body segment inertial parameter (BSIP) estimates due to differences in body composition, and this may influence calculation of joint kinetics. The purposes of this study were to (1) compare BSIPs predicted by the method introduced by de Leva1 with DXA-derived BSIPs in collegiate female soccer players, and (2) examine the effects of these BSIP estimation methods on joint moment and power calculations during a drop vertical jump (DVJ). Twenty female NCAA Division I soccer players were recruited. BSIPs of the shank and thigh (mass, COM location, and radius of gyration) were determined using de Leva's method and analysis of whole-body DXA scans. These estimates were used to determine peak knee joint moments and power during the DVJ. Compared with DXA, de Leva's method located the COM more distally in the shank (P = .008) and more proximally in the thigh (P < .001), and the radius of gyration of the thigh to be further from the thigh COM (P < .001). All knee joint moment and power measures were similar between methods. These findings suggest that BSIP estimation may vary between methods, but the impact on joint moment calculations during a dynamic task is negligible.

Tripping Elicits Earlier and Larger Deviations in Linear Head Acceleration Compared to Slipping.

Slipping and tripping contribute to a large number of falls and fall-related injuries. While the vestibular system is known to contribute to balance and fall prevention, it is unclear whether it contributes to detecting slip or trip onset. Therefore, the purpose of this study was to investigate the effects of slipping and tripping on head acceleration during walking. This information would help determine whether individuals with vestibular dysfunction are likely to be at a greater risk of falls due to slipping or tripping, and would inform the potential development of assistive devices providing augmented sensory feedback for vestibular dysfunction. Twelve young men were exposed to an unexpected slip or trip. Head acceleration was measured and transformed to an approximate location of the vestibular system. Peak linear acceleration in anterior, posterior, rightward, leftward, superior, and inferior directions were compared between slipping, tripping, and walking. Compared to walking, peak accelerations were up to 4.68 m/s2 higher after slipping, and up to 10.64 m/s2 higher after tripping. Head acceleration first deviated from walking 100-150ms after slip onset and 0-50ms after trip onset. The temporal characteristics of head acceleration support a possible contribution of the vestibular system to detecting trip onset, but not slip onset. Head acceleration after slipping and tripping also appeared to be sufficiently large to contribute to the balance recovery response.