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The influence of load carriage and foot stiffness on knee joint loading and metabolic cost during amputee walking
No full textIndividuals experience sudden load changes during activities of daily living. This added weight places an increased demand on the muscles providing body support, forward propulsion and balance control. For non-amputees, the mechanical output from the ankle muscles are seamlessly modulated to meet the altered demands of load carriage. However, for individuals with a lower-limb amputation, the stiffness properties of standard-of-care prosthetic feet are constant and do not change with varying load conditions. Thus, lower limb amputees often develop gait asymmetries to compensate for the loss of ankle muscles, which may be exacerbated by load carriage. These asymmetries may increase the risk for developing overuse injuries and osteoarthritis in the intact knee as well as elevate the metabolic cost of walking relative to non-amputees. Unfortunately, it is not well understood how prosthetic foot stiffness and load carriage technique influences joint loading asymmetries during amputee gait. The purpose of this study was to use a forward dynamics simulation framework to assess the influence of load carriage technique and prosthetic foot stiffness on knee joint loading and metabolic cost during amputee gait. Forward dynamics simulations were generated to track experimental amputee walking data for each loading condition (unloaded, with a backpack, and with a frontpack) and prosthetic foot condition (four commercially available elastic energy storage and return (ESAR) feet). The results of these simulations showed that amputees rely on their intact limb as a compensatory strategy to meet the increased demands of carrying a load. Carrying the load in a backpack was found to reduce metabolic cost but increase intact knee joint loading. When varying prosthetic foot stiffness, there was no consistent effect on metabolic cost or knee joint loading in any of the three loading conditions. Future work should focus on designing prosthetic components that help reduce the joint loading asymmetry and elevated metabolic cost during load carriage for lower limb amputees. In addition, the tradeoff between metabolic cost and joint loading should be considered when determining the appropriate load carriage technique.Mechanical Engineerin
MARKERLESS MOTION CAPTURE AND OPTIMAL CONTROL TO INFORM PITCHING MECHANICS AND REDUCE INJURY RISK
No full textThe objective of this study is to demonstrate the utility of predictive musculoskeletal simulations in baseball pitching. An optimal control analysis was developed that aimed to minimize injury risk while maintaining pitching performance. The optimization converged on a solution that reduced peak shoulder internal rotation by 27.1% while maintaining peak hand velocity within 1.7%. The optimized simulation suggested that 1) a lower arm slot 2) greater knee extension in the stride leg would lead to reduced injury risk without degrading performance. This study\u27s findings demonstrate the potential of biomechanical analyses in enhancing performance and reducing injury risks in baseball pitchers
The Influence of Load Carriage on Knee Joint Loading and Metabolic Cost on Walking with Lower-Limb Amputation: A Preliminary Modeling Study
No full textMagnesium Battery Electrolytes in Ionic Liquids
No full textabstract: A lack of adequate energy storage technologies is arguably the greatest hindrance to a modern sustainable energy infrastructure. Chemical energy storage, in the form of batteries, is an obvious solution to the problem. Unfortunately, today’s state of the art battery technologies fail to meet the desired metrics for full scale electric grid and/or electric vehicle role out. Considerable effort from scientists and engineers has gone into the pursuit of battery chemistries theoretically capable of far outperforming leading technologies like Li-ion cells. For instance, an anode of the relatively abundant and cheap metal, magnesium, would boost the specific energy by over 4.6 times that of the current Li-ion anode (LiC6).
The work presented here explores the compatibility of magnesium electrolytes in TFSI–-based ionic liquids with a Mg anode (TFSI = bis(trifluoromethylsulfonyl)imide). Correlations are made between the Mg2+ speciation conditions in bulk solutions (as determined via Raman spectroscopy) and the corresponding electrochemical behavior of the electrolytes. It was found that by creating specific chelating conditions, with an appropriate Mg salt, the desired electrochemical behavior could be obtained, i.e. reversible electrodeposition and dissolution. Removal of TFSI– contact ion pairs from the Mg2+ solvation shell was found to be essential for reversible electrodeposition. Ionic liquids with polyethylene glycol chains pendent from a parent pyrrolidinium cation were synthesized and used to create the necessary complexes with Mg2+, from Mg(BH4)2, so that reversible electrodeposition from a purely ionic liquid medium was achieved.
The following document discusses findings from several electrochemical experiments on magnesium electrolytes in ionic liquids. Explanations for the failure of many of these systems to produce reversible Mg electrodeposition are provided. The key characteristics of ionic liquid systems that are capable of achieving reversible Mg electrodeposition are also given.Dissertation/ThesisDoctoral Dissertation Chemistry 201
The effect of feed additive program in steam-flaked corn diets containing wet distiller's grains on performance and carcass merit in yearling feedlot steers
No full text2011 Spring.Includes bibliographical references.Crossbred yearling steers (432, BW = 329 ± 10.5 kg) were used in an unbalanced randomized block design to examine the effect of feed additives on performance and carcass merit. Treatment factors were arranged as a 2 x 2 factorial and included ionophore and antibiotic [Rumensin/Tylan (R/T) or Cattlyst/Aureomycin (C/A)] and dietary S (constant or variable). High S diets were fed on random days to the variable (VAR) treatment. Low S diets were fed to the VAR treatment on remaining days and to the constant (CON) treatment all days. From d 0 through 35, the high S diet was achieved by using a high S granular supplement; however, since S concentration in wet distillers grains (WDG) is associated with distillers solubles (DS) added to WDG and H2SO4 added to the DS, the high S diet was achieved from d 36 through 159 by using a DS based liquid supplement with 2.35% S while the low S diet was achieved using a 0.99% S DS based liquid supplement. Cause of cattle death for study steers was verified by necropsy. No interaction between S and additive treatments existed for feedlot performance; therefore, only main effects are presented. Most of the sulfur comparisons from this study will be addressed in another manuscript. Feedlot performance and carcass merit were similar for feed additive treatments. The S by feed additive interaction was significant (P < 0.05) for dressing percentage indicating that S treatment had no effect on dressing percentage if R/T was fed but when steers were fed C/A, dressing percentage was reduced by 0.72% (P < 0.02) if VAR diets were fed. The results of this study indicate that performance and carcass characteristics for cattle fed Cattlyst and Aureomycin are similar to performance and carcass characteristics for cattle fed Rumensin and Tylan
Identifying special operative trainees at-risk for musculoskeletal injury using full body kinematics
No full textIntroduction: Non-combat musculoskeletal injuries (MSKIs) during military training significantly impede the US military’s functionality, with an annual cost exceeding $3.7 billion. This study aimed to investigate the effectiveness of a markerless motion capture system and full-body biomechanical movement pattern assessments to predict MSKI risk among military trainees.Methods: A total of 156 male United States Air Force (USAF) airmen were screened using a validated markerless biomechanics system. Trainees performed multiple functional movements, and the resultant data underwent Principal Component Analysis and Uniform Manifold And Projection to reduce the dimensionality of the time-dependent data. Two approaches, semi-supervised and supervised, were then used to identify at-risk trainees.Results: The semi-supervised analysis highlighted two major clusters with trainees in the high-risk cluster having a nearly five times greater risk of MSKI compared to those in the low-risk cluster. In the supervised approach, an AUC of 0.74 was produced when predicting MSKI in a leave-one-out analysis.Discussion: The application of markerless motion capture systems to measure an individual’s kinematic profile shows potential in identifying MSKI risk. This approach offers a novel way to proactively address one of the largest non-combat burdens on the US military. Further refinement and wider-scale implementation of these techniques could bring about substantial reductions in MSKI occurrence and the associated economic costs
Community-based postural control assessment in autistic individuals indicates a similar but delayed trajectory compared to neurotypical individuals
No full textAutistic individuals exhibit significant sensorimotor differences. Postural stability and control are foundational motor skills for successfully performing many activities of daily living. In neurotypical development, postural stability and control develop throughout childhood and adolescence. In autistic development, previous studies have focused primarily on individual age groups (e.g., childhood, adolescence, adulthood) or only controlled for age using age-matching. Here, we examined the age trajectories of postural stability and control in autism from childhood through adolescents using standardized clinical assessments. In study 1, we tested the postural stability of autistic (n = 27) and neurotypical (n = 41) children, adolescents, and young adults aged 7–20 years during quiet standing on a force plate in three visual conditions: eyes open (EO), eyes closed (EC), and eyes open with the head in a translucent dome (Dome). Postural sway variability decreased as age increased for both groups, but autistic participants showed greater variability than neurotypical participants across age. In study 2, we tested autistic (n = 21) and neurotypical (n = 32) children and adolescents aged 7–16 years during a dynamic postural control task with nine targets. Postural control efficiency increased as age increased for both groups, but autistic participants were less efficient compared to neurotypical participants across age. Together, these results indicate that autistic individuals have a similar age trajectory for postural stability and control compared to neurotypical individuals, but have lower postural stability and control overall.Lay SummaryAutistic and neurotypical children and adolescents performed a balance test and a body control test. Autistic participants had less stable balance than neurotypical participants. Autistic and neurotypical participants had less stable balance with their eyes closed and when wearing a dome on their head. Neurotypical participants had better body control than autistic participants. Autistic and neurotypical children had less stable balance and body control than adolescents.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/176082/1/aur2889_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/176082/2/aur2889.pd
RELATIONSHIP BETWEEN KINEMATIC SEQUENCE CHARACTERISTICS, UPPER EXTREMITY JOINT WORK, AND FREE-THROW SHOOTING ACCURACY
No full textThis study investigates the relationship between kinematic sequence variables and upper extremity joint work in basketball free-throw shooting. Thirty-four participants performed free-throw shots, analyzed using a 3D markerless motion capture system (ENABLE). The study focused on the timing of peak segmental angular velocities and their relation to joint work in the shooting shoulder and elbow. Significant correlations were found between the timing of peak angular velocities and upper extremity joint work. The findings suggest that proficient basketball shooters demonstrate a more efficient kinematic sequence, characterized by longer duration of time between knee, pelvis, and elbow peak angular velocities and reduced upper extremity workload. This study underscores the importance of understanding the biomechanics of shooting for training and skill development in basketball
Biomechanical characteristics of proficient free-throw shooters—markerless motion capture analysis
No full textThe winning game outcome in basketball is partially contingent on the team's ability to secure and make more free-throw shooting attempts, especially close to the end of the game. Thus, the purpose of the present study was to perform a comprehensive biomechanical analysis of the free-throw shooting motion to examine differences between (a) proficient (≥70%) and non-proficient shooters (<70%) and (b) made and missed free-throw shoots within the proficient group of shooters. Thirty-four recreationally active males with previous basketball playing experience attempted ten consecutive free-throw shots (4.57 m), with a 10–15 s rest interval between each shot. An innovative three-dimensional markerless motion capture system (SwRI Enable, San Antonio, TX, USA) composed of nine high-definition cameras recording at 120 Hz was used to capture and analyze the biomechanical parameters of interest. Independent t-tests and Mann–Whitney U tests were used to examine a presence of statistically significant differences. The findings of the present study reveal that proficient free-throw shooters performed the shooting motion in a more controlled manner by having significantly lower knee and center of mass peak and mean angular velocities. Also, proficient shooters attained a significantly greater release height and had less forward trunk lean when compared to non-proficient shooters at the time point of the ball release. Moreover, despite being beneficial for improvements in shooting accuracy, our findings suggest that overemphasizing the release height may be in certain instances counterproductive, as it may lead to more missed than made free-throw shots within the proficient group of shooters
Characterizing goal-directed whole-body movements in autistic children and children with developmental coordination disorder
No full textBackground Motor difficulties are highly prevalent in neurodevelopmental conditions. Both autistic children and children with developmental coordination disorder exhibit clinically-significant motor difficulties with substantial differences in postural control. Postural control has been examined extensively in these groups independently, but there has been little research comparing them in the same study. Methods We examined dynamic postural control in autistic children, children with developmental coordination disorder, and neurotypical children using an immersive virtual reality task. Children moved a user-controlled ball to a static target using whole-body movements. Results Children in all three groups were able to move their ball to the target successfully, but there were significant differences in their movement characteristics (e.g., trial duration, path efficiency, log dimensionless jerk, movement types). There was a similar trend for each of the movement characteristics: autistic children performed significantly worse than neurotypical children, and children with developmental coordination disorder had varied performance compared to neurotypical and autistic children. Conclusion These findings provide clear support for our hypotheses that autistic children have difficulty with goal-directed whole-body movements, and that these movements are similarly different from neurotypical children’s movements. They provide mixed support for our hypothesis that children with developmental coordination disorder differ in their goal-directed body movements. By understanding the similarities and differences in motor difficulties across neurodevelopmental conditions, we can begin to develop motor interventions specifically targeted to the unique motor profiles of these populations
