Download or read book Influence of Thigh Muscle Forces on Anterior Cruciate Ligament Forces During Single leg Landing from Three Different Heights written by Jonathan M. Bulluck and published by . This book was released on 2010 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over 200,000 anterior cruciate ligament (ACL) injuries occur every year amounting to billions of dollars being spent on the ACL annually. While the quadriceps muscle produces an anterior shear force on the tibia that causes the ACL to strain, the hamstrings muscle can protect the ACL by producing a posterior shear force to the tibia reducing the strain. When the hamstrings contract simultaneously with the quadriceps, ACL strains are considerably less compared to isolated quadriceps forces, thus the balance of hamstring and quadriceps muscle forces play a critical role in determining the forces on the ACL. During dynamic landing tasks, quadriceps demands increase as the landing height increases, which may cause the ACL to be more susceptible to injury. The purpose of this study was to determine the relationship of the quadriceps and hamstring muscle forces on ACL forces during single-leg landing from three different heights. We hypothesized that the ratio between hamstrings and quadriceps muscle forces would be negatively correlated to peak ACL forces during landing from three different heights. We anticipated that the hamstring to quadriceps ratio would decrease as landing height increased primarily due to the increased quadriceps demands. Three males with an average height of [1].75"0.07m with an average mass of 74.08"8.66kg and three females with an average height of 1.70"0.04m and an average mass of 55.93"6.83kg landed on their right leg from three different heights, 15cm, 30cm, and 45cm. Musculoskeletal modeling was used to estimate muscle forces. Regression analyses predicted the ACL forces from all three heights, and the heights pooled together. The results showed that the quadriceps muscles forces were strongly positively correlated to the peak ACL force while the hamstrings muscle forces were not significantly correlated to peak ACL force. Linear analysis showed the hamstring to quadriceps ratio to be moderately negatively correlated with peak ACL force (r2 = 0.278), but nonlinear curve analysis showed a stronger relationship between these variables (r2 = 0.425). However, as the landing height increased, these linear and nonlinear relationships both decreased. This signifies that another factor was contributing to the peak ACL force especially at higher heights. The combined influence of ground reaction forces and the hamstring to quadriceps ratio revealed that as landing height increased the ground forces became more of a factor in predicting peak ACL forces compared to the hamstring to quadriceps ratio being the dominant predictor at the lowest heights. In conclusion, the data support our hypothesis the hamstring to quadriceps ratio was inversely related to the peak ACL force although the strength of this relationship was height dependent. Further, as landing height increases, the ground reaction forces become the stronger predictor of peak ACL forces compared to the hamstring to quadriceps force ratio.

Download or read book Predicting Risk Factors of Non Contact Anterior Cruciate Ligament Injuries During Single Leg Landing written by Ali Nicholas and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The literature suggests that body kinematics and musculoskeletal differences are major factors contributing to the high disparity in non-contact Anterior Cruciate Ligament (ACL) injury rate between genders. The literature also indicates that the incidence of non-contact ACL injury predominates during single-leg landing sports such as basketball, soccer, and handball. Despite this, there are few studies investigating kinematics or musculoskeletal differences between genders during single-leg landing from increasing vertical heights and horizontal distances. The objectives of this study are threefold: first, conduct a gap study identifying the barriers to predicting mechanisms and risk factors for non-contact ACL injury. Second, propose a new approach that can address some of the challenges encountered in some existing non-contact ACL injury study approaches. Finally, whilst determining whether or not gender differences explain the higher rate of ACL injuries among females, identify and correlate the biomechanical and musculoskeletal variables significantly impacted by gender, vertical landing height, and/or horizontal landing distance and their interactions to various ACL injury risk predictor variables during single-leg landing. Experiments using male and female subjects, inverse dynamics analysis using Visual3D, and musculoskeletal modeling simulation using AnyBody Modeling System were approaches used to explore these objectives. Salient findings from this dissertation includes but are not limited to, non-contact ACL injury that occurs during single-leg landing is mutifaceted entailing many factors that cannot be captured in any one existing ACL injury study approach. Non-contact ACL injury during single-leg landing may not be gender specific. Both vertical height and horizontal distance of landing increase the risk of non-contact ACL injury during single-leg landing. Body kinematics during single-leg landing may not be the sole determinant in attenuating ground reaction forces and consequently risk of ACL injury. The hamstring and gastrocnemius muscles were determined to strain shield the ACL while the quadriceps were found to have no significant effect on risk of ACL injury during single-leg landing. Within the findings and limitations of this study the knowledge garnered from this research may aid in tailoring future studies so as to enable more robust non-contact ACL injury prevention protocols.

Download or read book The Effect of Sagittal Plane Mechanics on Anterior Cruciate Ligament Strain During Jump Landing written by Ryan Bakker and published by . This book was released on 2014 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Anterior cruciate ligament (ACL) is an important ligament in the knee. Non-contact ACL injuries are a common occurrence among athletes, leading to large financial burdens and long term physical concerns. The underlying biomechanics leading to these non-contact ACL injuries are unknown, in part due to limited experimental studies investigating the mechanics of dynamic activities. Understanding these mechanics is critical for injury prevention and risk analysis. The primary objective of this study was to investigate the underlying sagittal plane mechanics leading to increasing ACL strain during jump landing. A hybrid in-vivo/computational/in-vitro approach was used to measure ACL strain in relation to these mechanics. Motion capture was performed on ten subjects performing a single leg jump landing and both whole-body kinematics and ground reaction forces were collected. Musculoskeletal models were driven using this data to estimate the lower limb muscle forces from the jump landing. Five cadaver knee specimens were instrumented to measure ACL strain and mounted on a dynamic knee simulator. Muscle forces and sagittal plane kinematics were then applied on the cadaver specimens, dynamically recreating the activity. Strain in the anterior cruciate ligament was measured for each simulation. Bivariate correlation and multivariate linear regression analyses were performed with both maximum ACL strain and time to maximum ACL strain with the sagittal plane mechanics measured during the motion capture. Correlation analysis found increasing ACL strain was correlated with increasing ground reaction forces, increasing body weight, decreasing hip flexion angles, increasing hip extension moments, and increasing trunk extension moments, among others. Time to max ACL strain was correlated with increasing knee flexion angles and increasing knee angle velocities. The multivariate linear regression revealed anatomical factors account for most of the variance in maximum ACL strain, but suggests landing softly by increasing joint angles and absorbing impact, are important strategies for reducing ACL strain. Time to max ACL strain regression was influenced by anatomic factors and knee velocities. An athlete may have little or no control over the anatomic factors contributing to ACL strain, but altering their landing strategy to reduce the chance of injury. The empirical relationship developed between increasing joint angles, energy absorption and ACL strain in this study could be used to estimate the relative strain between jumps and to develop training programs designed to reduce an athlete's risk of injury.

Download or read book The Influence of Femoral Structure Hip Capsular Constraints and Gluteal Muscle Strength and Activation on Temporal Patterns of Functional Valgus Collapse written by Jennifer A. Hogg and published by . This book was released on 2018 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Functional valgus collapse (a combination of knee abduction and internal rotation and hip adduction and internal rotation) is a modifiable lower extremity movement pattern commonly associated with anterior cruciate ligament (ACL) injuries in females. Though the gluteus maximus and gluteus medius have frequently been named contributors to functional valgus collapse, evidence supporting their role in lower extremity movement has been inconsistent, and could in part be due to methodological differences between studies and the accepted practice of analyzing discrete variables instead of overall movement patterns. Better elucidation of gluteal muscle influence on lower extremity biomechanics may be a critical step for the reduction of ACL injury rates, as neuromuscular dysfunction is likely more responsive to injury prevention efforts than are other risk factors such as bony anatomy, ligament quality, or hormonal influences, that are more difficult to modify. Therefore, the purpose of this study was to 1) describe the neuromechanical profiles throughout the landing phase of single-leg and double-leg forward landings in males and females, 2) quantify the contributions of gluteal muscle strength and activation to peak angles and moments of functional valgus collapse after controlling for one's femoral alignment, and 3) explore the association between gluteal muscle function and overall functional valgus collapse throughout the landing phase. To accomplish this, 45 females and 45 males with no history of knee surgery were measured for femoral anteversion, hip ROM, and hip strength and then underwent biomechanical testing during single-leg and double-leg forward landings to examine muscle activation and 3-dimensional biomechanics. Data were analyzed using conventional group and correlative analyses and also with statistical parametric mapping (SPM), which allowed for a more comprehensive examination of the entire biomechanical time series. Biomechanical variables of interest included joint angles and moments comprising functional valgus collapse: hip adduction and internal rotation and knee abduction and internal rotation. In the comparison between single-leg and double-leg landings by sex, sex differences in the frontal plane were task dependent, though females maintained greater absolute knee abduction and hip adduction throughout the landing phases. Sex by task interactions revealed that females landed with smaller knee adduction angles than males, particularly during the single-leg landing (p=.03), while females' knee abduction excursion was greater than males', particularly during the double-leg landing (p=.01). Across task, females displayed 4.1° greater peak knee abduction than males (p=.002), and this was specific to 37-46% of the landing phase (p=.05). Females went through 1.0° more hip abduction than males (p=.05), and used a smaller proportion of their gluteus maximus (p=.01) in both tasks. Examination of gluteal muscle contribution to individual and overall levels of functional valgus collapse in females revealed that at the 18% and 20% time points during the landing phase, less hip abduction strength and greater gluteus medius activation predicted greater peak hip adduction angles (R2 change = .10; p = .02) and higher external hip adduction moments (R2 change = .14, p = .06). Greater hip extension strength predicted greater peak hip abduction angles (R2 change = .08; p = .05), while greater gluteus maximus activation strengthened the prediction of greater initial (R2 change = .10, p = .03) and peak (R2 change = .14, p = .01) knee internal rotation angles. From 7% - 8% of the landing phase, greater external rotation ROM was associated with greater external hip adduction moment (R2 change = .18, p = .01). In males, less hip abduction strength strengthened the prediction of greater initial (R2 change = .12, p = .01) and peak knee internal rotation angles (R2 change = .14, p = .01), lesser peak knee external rotation angles (R2 change = .07, p =.09), and lesser peak knee abduction moments (R2 change = .06, p =.11). Less hip extension strength with greater gluteus maximus activation predicted greater peak hip external rotation moments (R2 change = .14, p = .01). Specifically from the 3% - 9% time points of the landing phase, greater hip extension strength was associated with greater knee abduction moment (R2 change = .17, p = .01) and less hip adduction moment (R2 change = .24, p = .001). At 0% and from 2% - 3% of the landing phase, greater internal and external rotation ROM were associated with greater knee abduction angle (R2 change = .27, p = .01) and greater hip adduction angle (R2 change = .23, p = .02). These results indicate that lower extremity biomechanics during a single-leg landing task are appreciably different than those observed during a double-leg landing task, and that a single-leg landing task elicits more profound sex differences, particularly during the early stage of single-leg load acceptance when ACL injuries are thought to occur (30-40ms post initial ground contact). As such, a single-leg landing task may be more appropriate for biomechanical screening of ACL injury risk. Gluteal strength and activation explained a unique proportion of variance in lower extremity biomechanics beyond what was explained by femoral alignment. In females, weaker gluteal muscles predicted riskier frontal plane hip kinematics. In males, gluteal function was more associated with kinetics. This implies that our male cohort used their musculature to create torque about a joint, whereas our female cohort was unable to create torque. Though femoral alignment (total ROM) explained considerably greater proportions of biomechanical variance than did gluteal function, observed associations between gluteal muscle function and biomechanics occurred 10-20ms after associations between femoral alignment and biomechanics. While the gluteal muscles may act mechanically independent of femoral alignment, it is possible that gluteal muscle function could be temporally linked to one's femoral alignment. With these findings in mind, it may be beneficial for clinicians to implement gluteal strengthening programs and to encourage gluteal muscle pre-activation in individuals with excessive hip ROM to lessen their propensity for functional valgus collapse."--Abstract from author supplied metadata.

Download or read book Dynamic Simulations and Data Mining of Single leg Jump Landing written by Kristin Denise Morgan and published by . This book was released on 2014 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is estimated that 400,000 anterior cruciate ligament (ACL) injuries occur in the United States each year with the cost of ACL reconstruction surgery and rehabilitation exceeding $1 billion annually. The majority of ACL injuries are non-contact injuries occurring during cutting and jump landing movements. Because the majority of the injuries are non-contact injuries there is the potential to develop programs to reduce the risk of injury. Given our understanding of the joint kinematics and kinetics that place an individual at high risk for ACL, researchers have developed neuromuscular training programs that focus on improving muscle function in order to help the muscles support and stabilize the knee during the dynamic movements that increase the strain on the ACL. Yet, despite the implementation of these neuromuscular-based ACL injury training intervention programs ACL rates continue to rise. Thus the objective of this dissertation is to determine the cause and effect relationship between joint biomechanics and muscle function with respect ACL injury. There are four studies in this dissertation. The first two studies rely heavily on the development of subject-specific musculoskeletal models to analyze muscle contribution during single-leg jump landing. These studies will generate forward dynamic simulations to estimate muscle force production and contribution to movement. The results of these studies will aid in the development of muscle-targeted ACL injury training intervention programs. The last two studies will employ data mining techniques; such as, principal component analysis (PCA) and wavelet analysis along with stability methods from control theory, to evaluate an individual’s risk of ACL injury and determine how muscle function differs for individuals at varying levels of injury risk. The goal will be to use this information to develop a more robust ACL injury prescreening tool. The use of both dynamic simulations and data mining techniques provides a unique approach to investigating the relationship between joint biomechanics and muscle function with respect to ACL injury. And this approach has the potential to gain much needed insight about the underlying mechanism of ACL injury and help progress ACL research forward.

Download or read book The Influence of Hamstring Musculo articular Stiffness on Biomechanical Factors Indicative of Anterior Cruciate Ligament Loading written by Justin Phillip Waxman and published by . This book was released on 2017 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Noncontact anterior cruciate ligament (ACL) injuries commonly occur upon initial foot contact (IC) with the ground during single-leg cutting or jump-landing maneuvers. Because these injuries occur in the absence of physical contact with another player or object, it is believed that some of these injuries may be avoided through intervention strategies aimed to target modifiable injury risk factors. In this regard, hamstring musculo-articular stiffness (KHAM) may play a critical role in protecting the ACL during functional athletic movements by helping resist biomechanical characteristics indicative of ACL loading, such as proximal tibia anterior shear force (PTASF), anterior tibial translation (ATT), and anterior tibial acceleration (ATA). However, current evidence regarding the influence of KHAM on knee joint biomechanics is limited to studies of non-weight bearing perturbations and double-leg landing tasks, which may not adequately represent the single-leg landing situations in which noncontact injuries commonly occur. Additionally, males and females have been included in the same analyses without accounting for between-sex differences that may confound reported relationships. Thus, the purposes of this study were to: 1) compare the neuromuscular and biomechanical demands of a double-leg stop-jump (DLSJ) task to that of a single-leg stop-jump (SLSJ) task in males and females; 2) determine, within each sex, the extent to which KHAM predicts ACL-loading characteristics during a SLSJ, after controlling for initial body positioning (i.e. trunk center-of-mass position and hip and knee flexion angles at IC); and 3) examine the extent to which a select group of anatomical, neuromuscular, and biomechanical characteristics collectively predict ACL-loading characteristics during a SLSJ. Eighty healthy, physically-active, males (n = 40) and females (n = 40) completed a 5-min warm-up, were measured for anterior knee laxity (AKL), quadriceps and hamstring maximal voluntary isometric contractions (MVIC), and KHAM, and then performed the DLSJ and SLSJ tasks, during which biomechanical and neuromuscular activation data were collected. Compared to the DLSJ, males and females performed the SLSJ with a more posterior trunk center-of-mass position (P

Download or read book ACL Strain During Single leg Jump Landing written by Anna Maria Polak and published by . This book was released on 2018 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: The anterior cruciate ligament (ACL) is a commonly-injured ligament in the human knee joint. ACL injury repair is a costly procedure; however, left unrepaired, ACL injuries can lead to complications later in life. In order to understand ACL injury, metrics such as strain in the ACL are measured under various loading conditions. A motion which has potential to cause ACL injury, a single leg jump landing, was replicated and ACL strain was recorded. Two common approaches for this purpose are in-vitro studies involving cadavers, and finite element (FE) modelling of the knee joint. Once ACL strain during the potentially injurious motion is evaluated, it is easier to work towards potential improvements to protective or rehabilitative equipment, such as knee braces. The objective of the current study was to measure ACL strain during a single leg jump landing using two different methods: 1. In-vitro experiments involving cadavers: - ACL strain vs. time was measured with unbraced and braced cadaver knees. 2. Finite element modelling of the human knee: - The finite element model was assessed using the in-vitro experiments, and can potentially be used to evaluate braced knee conditions in the future. The inputs for the experiments and finite element model were taken from motion capture, which was done in-vivo on two participants in a previous study. The two participants provided input kinetics and kinematics of a single-leg jump landing. The kinematic and kinetic inputs were then applied to three cadaveric specimens using the dynamic knee simulator (DKS) at the University of Waterloo, and ACL strain relative to the beginning of the trial was measured. The cadaver knees were also tested wearing an Össur CTi Custom knee brace, and the effect of the knee brace on relative ACL strain was measured. A finite element model of the human knee joint was also investigated by extracting the right leg of an existing full human body model, the Global Human Body Model Consortium (GHBMC) average-sized male (M50) model, and updating some of the tissue mechanical properties. The same boundary conditions from the experimental iv study were applied to the GHBMC right leg model, and relative ACL strain was calculated and compared against the experimental data. The experimental maximum relative ACL strain for an unbraced full jump landing was 0.032 and 0.057 for participant #1 input and 0.062 for participant #2 input. The computational maximum relative ACL strain was 0.042 for participant #1 input and 0.139 for participant #2 input. The finite element model was able to replicate the experimental ACL strain vs. time curves reasonably well, with a mean squared error of less than 0.01 for all loading scenarios. The results of the unbraced vs. braced jump landing experiments showed that the knee brace had no effect on ACL strain. The mean squared error between unbraced and braced ACL strain vs. time curves was less than 0.0011 for all loading cases, which is a low error value when compared to strains in the range of 0.015- 0.089. The jump landing finite element model is an important first step in using finite elements to predict relative ACL strain during jump landing. Future research directions include study of factors affecting ACL strain, incorporating the knee brace into the finite element model to investigate possible improvements to the brace, and investigating the benefits of adopting a subject-specific geometry for the model.

Download or read book Examination of Lower Extremity Mechanics During Three Landing Tasks and Injury Prediction Ability of Those Models as Compared to a Functional Test written by Timothy George Coffey and published by . This book was released on 2015 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: Anterior cruciate ligament (ACL) ruptures are one of the most common knee ligament injuries suffered by both male and female athletes. These injuries are severe in nature and also have long-term impacts on activities of daily living. Significant research has been conducted utilizing a drop landing task to attempt to better understand the mechanics behind the injury and to help identify at-risk athletes for targeted intervention. However, there have not been any published standards for the height of the drop landing activity, and previous researchers have also raised some concerns about the ability of a drop landing task to replicate the landing mechanics of a sport-specific task. To examine possible differences in performance based on specific landing tasks, the first study compared the landing mechanics of male and female high school athletes in three different landing conditions (drop landing, DL; adjusted height drop landing, AHDL; and a vertical jump task, VJL) (Chapter 3). Thirty-seven (37) athletes completed bilateral landings in the three conditions, and their kinetic and kinematic landing mechanics were compared across conditions. For the male participants, maximum knee flexion during landing was greater in AHDL condition as compared to the DL and VJL conditions. Both male and female participants demonstrated greater hip adduction at impact and overall maximum value in the VJL condition as compared to the two drop landings. As drop landing tasks have been used to identify at-risk athletes, it was important to examine the three different tasks' ability to predict lower extremity ligamentous injuries, and whether those 3D motion analysis predictors were more precise than a quick clinical symmetry screening tool (Chapter 4). One-hundred-and-sixty-five (165) athletes completed the clinical symmetry screen, and a subgroup of thirty-seven (37) athletes completed the 3D motion analysis. All of these participants were surveyed for lower extremity ligamentous injuries over the course of a season. Due to a small number of reported injuries, none of the injury predictor models based on 3D motion analysis landing mechanics or the clinical symmetry screening tool were able to produce accurate predictor models of injury. Knee abduction moment has been shown to be one of the strongest predictors of ACL injuries, and due to the collection of bilateral kinetics for a previous study (Chapter 3), there was a need to examine differences in KAM between the three different landing tasks (Chapter 5). Ten (10) recreational athletes completed bilateral landings in the three conditions, with foot placement relative to force plates to enable KAM calculation. The participants did not demonstrate any difference in KAM between the three landing conditions; however, a test for constant variance showed that the AHDL resulted in significantly less variance in KAM than DL or VJL. The results of these studies suggest that while easy to standardize, a set height drop landing task does not produce identical landing mechanics to those from an adjusted height drop landing task or a vertical jump task. Further research is needed to create or justify standardized landing tasks for researchers to utilize that produce consistent results that best duplicate the landing mechanics athletes performed during sporting activities. While the landing mechanics demonstrated in the three tasks and the results from the clinical screening were not able to predict injuries, future studies should examine quick clinical screening tools to identify athletes at a high risk of injury.

Download or read book The Effect of Arm Posture and Descent Height on Landing Forces written by Anoop Kumar Polsani and published by . This book was released on 2006 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: Operators of mobile construction equipment (e.g., bulldozers, scrapers, etc.) often opt to descend out of the cabin in an irregular fashion without using proper egress methods, despite being trained on proper egress methods. The main objective of this research was to quantify and compare the effect of arm posture, landing style, and descent height on ground reaction forces, and acceleration at the ankle and knee by performing a laboratory study. Fifteen male subjects descended from three different descent heights (38.1, 50.8, and 63.5cm) using three different arm postures (arms to the side, arms front, and arms crossed) and landing on both legs at the same time, right leg first, and left leg first. The results demonstrated that with the increase in descent heights, the ground reaction forces, and accelerations at the ankle and knee increased. Landing with the arms out stretched horizontally in front of the body (arms front) resulted in higher ground reaction forces, peak resultant acceleration at the knee, and higher transmissibility between the ankle and the knee compared to the arms hanging to the side of the body. Although having the arms out front when landing may slightly reduce impact forces, this posture may help in maintaining balance upon landing. Landing with "both legs at same time" increased the GRF, whereas landing on one leg first followed by the other leg seemed to distribute the landing force over a longer period of time. Landing on one or two legs at the heights tested in this study resulted in ground reaction forces lower than injury threshold values for the ankle from previous research. However, descending from higher heights may result in impact forces approaching or exceeding injury threshold levels. Results from this study on the effect of arm posture and landing style may be helpful for training OE on egress at lower level heights, however, engineering controls may be needed at higher egress heights.

Download or read book Alpine Skiing Injuries written by Herbert Schoenhuber and published by Springer. This book was released on 2018-07-17 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides detailed information on the different forms of injury that are associated with training for and participation in Alpine skiing, covering risk factors and epidemiology, incidence, injury patterns, and, above all, preventive strategies and current management approaches. Conditions addressed in individual chapters include concussion, traumatic dislocations due to high-energy trauma or inappropriate movements, overuse injuries resulting from dry-land training or skiing on snow, the fractures typically associated with present-day Alpine skiing accidents, and musculoskeletal disorders. The importance of a sound understanding of biomechanics and physiological systems for the design of suitable training protocols and trauma prevention is clearly explained, and in-depth information and guidance are provided on training and testing for elite skiers and return to sporting activity following injury. Among the other topics addressed in individual chapters are the relationship of changes in skiing equipment over recent decades to particular types of injury and the potential consequences of exposure to hypobaric hypoxia and other stressors at high altitude. The book will be of great value to all medical professionals who work with or care for Alpine skiers, as well as for trainers and the skiers themselves.

Download or read book Sex Specific Neuromuscular and Kinematic Analysis of Unanticipated Single leg Landings In Young Athletes written by Nicholas Romanchuk and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Despite the higher incidence of anterior cruciate ligament injuries in pediatric female populations, limited research has investigated sex-differences in youth biomechanics. Furthermore, research involving jump mechanics typically requires participant to follow a set protocol, such as sticking the landing. To reduce variability and improve reliability, trails where participants fail to meet the required protocol are discarded; however, significant clinical findings may be elucidated from these trials. The purpose of this thesis was to provide a complete biomechanical analysis of unanticipated single-leg drop-jump landings in youth athletes. Thirty-two healthy youth athletes completed unanticipated single-leg drop-jump landings on their dominant limb. Trials where participants shifted foot position or touched the ground with the contralateral leg were categorized as failed. Drop-jump landings were time-normalized using landmarks within the drop-jump task. Statistical parametric mapping (SPM) determined time-varying sex-differences in muscle onset time, co-activation, kinematics and kinetics. Wilcoxon signed-rank tests and paired sample t-tests compared lower-limb kinematics, centre-of-mass excursion and muscle activation amplitudes during the successful and failed landings. A logistic regression model was also fit to predict the likelihood of a successful landing. SPM identified significantly greater trunk flexion angle in males during the deceleration, flight, and landing phase of the drop-jump. Greater quadriceps-gastrocnemius co-activation was identified during the flight phase in female participants and independent sample t-test identified longer muscle onset time in the vastus lateralis of male participants. When comparing failed and successful landings greater hip abduction and less external rotation angles were observed during the successful trials. In addition, greater preparatory muscle activation was observed in the rectus femoris and semitendinosus during the flight phase of the failed landings. A logistic regression model, which included eight kinematic and neuromuscular variables, offered a training classification accuracy of 70% and a leave-one-out cross-validation accuracy of 65%. In conclusion, females land in a more erect posture and may be less effective at dissipating landing forces. In addition, greater co-activation and shorter pre-activations of the lower limb musculature may indicate a less effective muscle activation strategy in females. Furthermore, hip kinematics and the surrounding musculature play an important role in controlling successful and failed unanticipated landings. The variables included in the logistic regression model indicate which key factors are linked to landing a jump successfully. Training modalities aimed at improving landing mechanics should therefore focus on modifying these variables.

Download or read book The Influence of Residual Fatigue on Lower Limb Stiffness During Jump Landing written by Lindsay Victoria Slater and published by . This book was released on 2010 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Background: Anterior cruciate ligament (ACL) injuries have become commonplace among female athletes in today's society. With more than 70% of injuries resulting from noncontact mechanisms such as jump landing, the relationship between fatigue and altered movements patterns has become an important topic of research. Purpose: The main purpose of this study was to investigate the influence of residual fatigue on lower extremity kinematics and vertical leg stiffness at landing as experienced by female athletes. Method: The participants in this study were 12 NCAA female intercollegiate soccer players. Participants completed five single-leg drop jumps on their dominant leg every day for 4 days. The first day was completed without intervention to obtain pre-fatigue data and drop jumps on days two through four were completed after a fatigue protocol. Results: A repeated measures MANOVA did not reveal significant differences in post-fatigue peak knee flexion angle, vertical ground reaction forces, or vertical leg stiffness. Despite lack of statistical significance, vertical leg stiffness was increased during post-fatigue testing when compared to pre-fatigue values. Implications: The increased vertical leg stiffness may indicate altered landing techniques in post-fatigue states. If fatigue results in compromised movement patterns, it may explain the increased number of ACL injuries during the end of soccer matches. Suggestions for Future Research: Future research with a larger sample size should include post-fatigue dominant and nondominant leg comparison due to previous conflicting findings regarding which limb is most often injured. Future researchers should also quantify the magnitude of fatigue induced by the fatiguing protocol to document the strength of the independent variable.

Download or read book Anatomical and Neuromuscular Contributions to Anterior Knee Shear Force During Single leg Landings in Females written by Thomas C. Windley and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "This research investigated the collective interactions between hamstrings extensibility, anterior knee laxity, and hamstrings and quadriceps muscle activation as predictors of anterior knee shear forces during single-leg landings in females. Forty-five healthy, recreationally active females participated in a single data collection session during which hamstrings muscle extensibility and anterior knee laxity were measured, followed by measurement of surface electromyography of the quadriceps and hamstrings and estimation of anterior knee shear forces during single-leg landings. Five single-leg drop landings were conducted from a 30 cm platform positioned 30% of the height of the participant behind the center of a force plate. Electromyographic data were normalized to maximum volitional isometric contractions at 30' of knee flexion, and forces were normalized to body weight. Multiple linear regression analyses were used to evaluate the ability of hamstrings extensibility, anterior knee laxity, and hamstrings and quadriceps pre- and post-landing activation amplitudes to predict initial, rate, and peak anterior knee shear forces during the landings. The primary findings were that hamstrings pre-landing activation negatively predicted anterior knee shear force at initial ground contact and positively predicted the rate of anterior knee shear force development following landing. Furthermore, peak anterior knee shear force following the landings was positively predicted by hamstrings post-landing activation and negatively predicted by hamstrings pre-landing activation. Anterior knee laxity, hamstrings extensibility, and quadriceps pre- and post-landing activations did not significantly add to the prediction of anterior knee shear forces. Hence, it was concluded that hamstrings activation was the primary predictor of anterior knee shear forces during single-leg landings in females."--Abstract from author supplied metadata.

Download or read book The Effect of Gluteus Medius Muscle Activation on Lower Limb Three dimensional Kinematics and Kinetics in Male and Female Athletes During Three Drop Jump Heights written by Stephanie Christine Nowak and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Women are four to eight times more likely to injure their anterior cruciate ligament (ACL) compared to men. It is most commonly injured through a non-contact mechanism during game time situations. During landings, women display valgus collapse, where a less active gluteus medius muscle (GMed) may be unable to control the internal rotation of the thigh, causing an increase in knee joint abduction angle, augmenting the risk of ACL injury. This study's purpose was to determine the difference between 12 male and 12 female athletes in muscle activity, specifically the GMed, and the 3D kinematics and kinetics of the lower-limb during drop jump landings from three heights; maximum vertical jump height, tibial length, and a commonly used height of 40cm. Results showed that females had greater hip adduction and knee abduction angles compared to men. The GMed activity showed no significant differences between sexes at each drop jump height.

Download or read book Human Muscle Fatigue written by Craig Williams and published by Routledge. This book was released on 2009-06-18 with total page 529 pages. Available in PDF, EPUB and Kindle. Book excerpt: When human muscle fatigues, athletic performance becomes impaired. For those individuals suffering muscle or metabolic diseases the effects of muscle fatigue can make everyday tasks difficult. Understanding the scientific processes responsible for skeletal muscle fatigue is therefore central to the study of the physiology of sport, exercise and health. Written by a team of leading international exercise scientists, this book explores the mechanisms of muscle fatigue and presents a comprehensive survey of current research on this important topic. Examining the wide variety of protocols, assessment methods and exercise models used to study muscle fatigue, the book explores the differential effects of fatigue as influenced by: age gender fitness and training the use of ergogenic aids medical conditions including cerebral palsy, muscular dystrophy and glycogenosis. Human Muscle Fatigue covers both clinical and applied approaches in sport and exercise physiology and devotes an entire section to the conceptual framework underpinning research in this area, helping readers from a wide range of backgrounds to engage with the topic. Accessible and detailed, this book is a key text for students and practitioners working in exercise and sports science, medicine, physical therapy and health.

Download or read book ACL Injuries in Female Athletes written by Robin West and published by Elsevier Health Sciences. This book was released on 2018-12-07 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: This easy-to-read reference presents a succinct overview of clinically-focused topics covering the prevention, treatment, and rehabilitation of ACL injuries in the female athlete. Written by two professional team physicians, it provides practical, focused information for orthopaedic and sports medicine surgeons and physicians. Covers ACL injury risk factors and prevention, including biomechanics, biology, and anatomy of the female athlete. Discusses graft choices, the biology of healing, rehabilitation and return to play, future options for treatment, and more. Addresses special considerations such as pediatric ACL and revision ACL. Consolidates today’s available information and experience in this timely area into one convenient resource.

Download or read book Understanding and Preventing Noncontact ACL Injuries written by American Orthopaedic Society for Sports Medicine and published by Human Kinetics Publishers. This book was released on 2007 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt: Grade level: 11, 12, i, s, t.