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Browsing by Author "Schmitt, Daniel"

Now showing 1 - 4 of 4
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    Development and Validation of Clinically Feasible Methods to Assess Landing Mechanics in Patients Following Anterior Cruciate Ligament Reconstruction
    Peebles, Alexander Thomas (Virginia Tech, 2020-06-09)
    Patients returning to sport after anterior cruciate ligament (ACL) reconstruction surgery currently have a high risk for sustaining a second ACL injury and having early signs of knee osteoarthritis. Assessing lower extremity kinetics and kinematics during landing can provide information about a patient's risk for sustaining a second ACL injury and having further joint trauma. However, currently accepted methods to assess kinetics and kinematics are not feasible to use in most non-research settings as they are expensive, time consuming, and take up a lot of space. The goal of this project was to identify methods to assess landing mechanics which are reliable and feasible to use in non-research settings. First, we found that the loadsol®, a wireless force sensing shoe insole, is valid relative to embedded force plates and repeatable between days for assessing kinetics and kinetic symmetry during bilateral and unilateral landing tasks. Second, we developed a new method to collect continuous kinematic data using a low-cost videocamera, disposable markers, and an automated point tracking program. This method was validated against a 3D motion capture system for measuring a fixed angle and for measuring sagittal plane running kinematics. Third, we found that the new video analysis method is valid relative to 3D motion capture and is repeatable between days for assessing frontal and sagittal plane knee kinematics during landing. Finally, we used the loadsol® and automated 2D video analysis to assess landing mechanics in both patients following ACL reconstruction and healthy uninjured control participants in a non-research setting. We found that, relative to controls, patients following ACL reconstruction had reduced kinetic symmetry during bilateral landing, where they offloaded their surgical limb and relied more heavily on their non-surgical limb. Additionally, patients following ACL reconstruction had reduced knee flexion range of motion symmetry during unilateral landing, where they had reduced knee flexion when landing on their surgical limb. Collectively, these projects developed methods to quantitatively assess landing mechanics that are feasible to use in non-research settings, documented the validity and between-day repeatability of these methods, and demonstrated that they could be used to identify kinetic and kinematic deficits in patients following ACL reconstruction. This project is an important step toward being able to assess landing mechanics in patients recovering from an ACL reconstruction.
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    Exploration of Movement Variability and Limb Loading Asymmetry During Simulated Daily Functional Tasks
    Streamer, Jill Evans (Virginia Tech, 2022-06-14)
    The human body is a complicated dynamic system that is difficult to model because of the numerous interactions that occur between limbs during various tasks. There are documented movement differences when assessing movement in various populations, for example, joint angle and loading symmetry differences when comparing a clinical and healthy population. Symmetry deficits can impact quality of life and in some cases have been associated with an increase in injury risk. Therefore, it is essential to understand movement and loading symmetry in healthy individuals to facilitate the identification of rehabilitation targets. The purpose of this research was to assess the impact that task type and sex have on movement variability and load symmetry in healthy younger adults. The tasks included in this study represent activities of daily living such as level walking, stair ascent, stair descent and standing up from a chair. A wireless, single-sensor in-shoe force sensor allowed for data collection in a non-laboratory setting so that peak impact force and average loading rate could be evaluated across the different daily tasks. To assess movement variability, the coefficients of variation (CV) were determined for each task. The peak impact force (PIF) did not show a significant interaction between sex and task (p=0.627) or between sexes (p=0.685). The PIF did show significant between-task differences (p < 0.001), where the highest mean CV was observed in the sit-to-stand task and the lowest CV was observed during level walking. The variation between movements could be a result of the differential motor skill required to perform the task. The average loading rate (ALR) did not show a significant interaction between sex and task (p=0.069) or between sexes (p=0.624). The average loading rate showed significant between-task differences (p < 0.001), where the highest mean CV was observed in the sit-to-stand task and the lowest CV was observed during level walking. Based on these results, differences in movement type needs to be considered when evaluating average loading rate. To assess the impact of task type on load symmetry, the absolute symmetry index was calculated for the peak impact force and the average loading rate. For both parameters, only between task differences were identified (p < 0.001) and further analysis showed that sit-to-stand was significantly different from the other three movement tasks. The acceptable threshold for a healthy level of asymmetry has been defined in a clinical population to be less than 10%. Based on a chi square analysis, the 10% threshold accurately represents 95% of the population when used to measure peak impact force in level walking, stair ascent and stair descent. However, when assessing peak impact force symmetry during sit-to-stand or assessing average loading rate symmetry between tasks, the 10% threshold does not consistently represent 95% of the population. These results indicate that a threshold for a healthy symmetry may need to be redefined for bilateral movements and that the symmetry threshold may need to be specific to the outcome measure of interest.
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    The Impact of Anterior Cruciate Ligament Reconstruction, Sex, and Sport-specific, Game-like Factors on Limb Stiffness and Limb Stiffness Asymmetry during Landing
    Teater, Michael Anthony (Virginia Tech, 2023-06-30)
    Non-contact injuries can occur when athletes use poor or inconsistent mechanics during typical sport-related movements like landing from a jump. Anterior cruciate ligament (ACL) injuries are especially devastating, and certain populations like female athletes and athletes with a previous ACL reconstruction (ACLR) are at greater risk of suffering an ACL injury, with altered biomechanical strategies being one proposed reason. Asymmetric landings where one limb experiences greater landing force can decrease joint stability and place the overloaded limb at greater risk for ACL injury. Additionally, a stiff landing, characterized by increased ground reaction force (GRF), extended joints at initial ground contact, and decreased joint flexion throughout the landing, has been proposed to increase ACL injury risk. While load distribution between limbs is a common landing assessment to determine injury risk, it is unclear what role limb stiffness plays in the likelihood of experiencing an ACL injury. Limb stiffness is simply the deformation of the limb in response to the downward force applied to the lower limb during ground contact, which can be approximated using GRF. Limb stiffness has been commonly used to assess performance in running, hopping, and jumping, however, its relationship with injury risk during landings is relatively unexplored. Past research has revealed that the ACL experiences peak strain prior to initial ground contact when the knee is at or near full extension. Additionally, expert video analyses have determined that ACL injuries most likely occur within 50 milliseconds of ground contact. It is possible that limb stiffness and limb stiffness asymmetry can be used during the early impact phase of landings to reveal ACLR- and sex-specific landing mechanics differences when the ACL appears to be most vulnerable. Moreover, game-like, sport-specific landing tasks with a greater horizontal component that load the ACL and those that divert attention away from landing strategies may uncover differences that do not appear in standard, controlled laboratory tasks. The overall goal of this project was to use limb stiffness, limb stiffness asymmetry, and related measures to analyze the early landing phase mechanics of groups at greater risk for ACL injury during game-like, sport-specific landings. First, in an ACLR cohort, greater knee power and knee work asymmetries were found when compared to healthy recreational athletes, supporting previous literature that found that athletes with an ACLR land unevenly by offloading their surgical limb. However, limb stiffness asymmetry was not different between groups, implying that the groups may have modulated limb stiffness differently between limbs. Second, minimal sex-by-task interactions were determined for landings that varied by horizontal approach prior to initial ground contact. Significant differences were found for most measures across tasks overall, however, male and female athletes displayed similar landing mechanics, indicating that expected sex-specific differences may not exist during the immediate landing phase when ACL injuries are thought to occur. Last a landing task that mimicked a ball in mid-air and diverted attention away from landing mechanics produced a sex-by-task interaction for peak impact force but no other measure. When comparing each sex-task pairing, a trend for greater peak impact force by female athletes during the distracted landing (p=0.098) was found which may indicate that future tasks with additional external focuses or another game-like component will reveal anticipated sex-specific differences. Increased time between limbs for initial ground contact for female athletes also revealed that a time-synchronized assessment of between-limb coordination may be beneficial for future research.
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    The Impact of Race and Related Factors on Movement Mechanics
    Hughes-Oliver, Cherice (Virginia Tech, 2020-05-06)
    Purpose: Race has rarely been the focus of biomechanics investigations, despite affecting the incidence of musculoskeletal injury and disease. Existing racial differences in movement mechanics could drive disease development and help identify factors contributing to racial health disparities. This study aimed to 1) Identify racial differences in walking, running, and landing mechanics between African Americans and white Americans and 2) Determine whether racial differences can be explained by anthropometric, strength, and health status factors. Methods: Venous blood samples, anthropometric measures, lower extremity strength, and a health status assessment were collected for 92 participants (18-30y) in an IRB approved study. After measuring self-selected walking speed, 3D motion capture and force plate data were recorded during 7 trials in the following conditions: regular walking (1.35m/s), fast walking (1.6m/s), running (3.2m/s), and drop vertical jump (31cm box height). Fundamental gait measures and running and landing measures associated with overuse and impact injury risk were extracted using Visual3D and custom Matlab scripts. Multivariate and post-hoc univariate ANOVA models were fit to determine main and interaction effects of gender and race (JMP Pro 15, α=0.05) after which data was separated by gender. Stepwise linear regression models evaluated whether anthropometric, strength, and health status factors explained racial effects. Results: Several racial differences in walking, running, and landing mechanics were observed in both men and women, but differed between genders. Effect sizes of observed racial differences indicate the potential for both statistical and clinical significance. Although several racial differences during all tasks were explained by anthropometric, strength, and health status factors in women, none were explained by these factors in men. In women, explanatory factors were a combination of innate and modifiable. Conclusion: Future steps should include the development of racially diverse databases and the identification of potential factors to target in interventions aimed at reducing racial health disparities.