Maximum dorsiflexion increases Achilles tendon force during exercise for midportion Achilles tendinopathy

Rehabilitation is an important treatment for non-insertional Achilles tendinopathy. To date, eccentric loading exercises (ECC) have been the predominant choice; however, mechanical evidence underlying their use remains unclear. Other protocols, such as heavy slow resistance loading (HSR), have shown comparable outcomes, but with less training time. This study aims to identify the effect of external loading and other variables that influence Achilles tendon (AT) force in ECC and HSR. Ground reaction force and kinematic data during ECC and HSR were collected from 18 healthy participants for four loading conditions. The moment arms of the AT were estimated from MRIs of each participant. AT force then was calculated using the ankle torque obtained from inverse dynamics. In the eccentric phase, the AT force was not larger than in the concentric phase in both ECC and HSR. Under the same external load, the force through the AT was larger in ECC with the knee bent than in HSR with the knee straight due to increased dorsiflexion angle of the ankle. Multivariate regression analysis showed that external load and maximum dorsiflexion angle were significant predictors of peak AT force in both standing and seated positions. Therefore, to increase the effectiveness of loading the AT, exercises should apply adequate external load and reach maximum dorsiflexion during the movement. Peak dorsiflexion angle affected the AT force in a standing position at twice the rate of a seated position, suggesting standing could prove more effective for the same external loading and peak dorsiflexion angle

Model-free Optimization of Trajectory And Impedance Parameters on Exercise Robots With Applications To Human Performance And Rehabilitation

This dissertation focuses on the study and optimization of human training and its physiological effects through the use of advanced exercise machines (AEMs). These machines provide an invaluable contribution to advanced training by combining exercise physiology with technology. Unlike conventional exercise machines (CEMs), AEMs provide controllable trajectories and impedances by using electric motors and control systems. Therefore, they can produce various patterns even in the absence of gravity. Moreover, the ability of the AEMs to target multiple physiological systems makes them the best available option to improve human performance and rehabilitation. During the early stage of the research, the physiological effects produced under training by the manual regulation of the trajectory and impedance parameters of the AEMs were studied. Human dynamics appear as not only complex but also unique and time-varying due to the particular features of each person such as its musculoskeletal distribution, level of fatigue,fitness condition, hydration, etc. However, the possibility of the optimization of the AEM training parameters by using physiological effects was likely, thus the optimization objective started to be formulated. Some previous research suggests that a model-based optimization of advanced training is complicated for real-time environments as a consequence of the high level of v complexity, computational cost, and especially the many unidentifiable parameters. Moreover, a model-based method differs from person to person and it would require periodic updates based on physical and psychological variations in the user. Consequently, we aimed to develop a model-free optimization framework based on the use of Extremum Seeking Control (ESC). ESC is a non-model based controller for real-time optimization which its main advantage over similar controllers is its ability to deal with unknown plants. This framework uses a physiological effect of training as bio-feedback. Three different frameworks were performed for single-variable and multi-variable optimization of trajectory and impedance parameters. Based on the framework, the objective is achieved by seeking the optimal trajectory and/or impedance parameters associated with the orientation of the ellipsoidal path to be tracked by the user and the stiffness property of the resistance by using weighted measures of muscle activations

Development of a user-centred design methodology to accommodate changing hardware and software user requirements in the sports domain

The research presented in this thesis focuses on the development of wireless, real time performance monitoring technology within the resistance training domain. The functionality of current performance monitoring technology and differences in monitoring ability is investigated through comparative force platform, video and accelerometer testing and analysis. Determining the complexity of resistance training exercises and whether performance variable profiles such as acceleration, velocity and power can be used to characterise lifts is also investigated. A structured user-centred design process suitable for the sporting domain is proposed and followed throughout the research to consider the collection, analysis and communication of performance data. Identifying the user requirements and developing both hardware and software to meet the requirements also forms a major part of the research. The results indicate that as the exercise complexity increases, the requirement for sophisticated technology increases. A simple tri-axial accelerometer can be used to monitor simple linear exercises at the recreational level. Gyroscope technology is required to monitor complex exercises in which rotation of the bar occurs. Force platform technology is required at the elite level to monitor the distribution of force and resultant balance throughout a lift (bilateral difference). An integrated system consisting of an Inertial Measurement Unit (both accelerometer and gyroscope technology) and a double plate force platform is required to accurately monitor performance in the resistance training domain at the elite level

Kinetics in Individuals with Unilateral Transtibial Amputations Using Running-Specific Prostheses

Improvements in rehabilitation and prosthetic design are needed to help promote activities such as running that increase physical activity levels of individuals with lower extremity amputation (ILEA). However, effectively developing these improvements requires a detailed understanding of prosthetic and ILEA running biomechanics. Running-specific prostheses (RSPs) have been developed to improve running performance for ILEA runners, but altered running kinetics may still be necessary to accommodate for the loss of musculoskeletal function caused by lower extremity amputation. The few studies investigating ILEA running with RSPs focus on maximal performance, but our understanding of how ILEA using RSPs modulate kinetics to run at submaximal velocities remains limited. The purpose of this study was to characterize changes in kinetics and mechanical energy across a range of running velocities in ILEA wearing RSPs. This dissertation investigated six specific aims through six corresponding experiments that improve our knowledge of mechanical and anthropometric properties of RSPs and the kinetic profiles of ILEA running at submaximal velocities. Four common RSP designs were tested for mechanical and anthropometric properties. ILEA with unilateral transtibial amputations who wear RSPs and an able-bodied control group participated in the running experiments. Mechanical and anthropometric results indicated that RSP marker placement had little effect on joint kinetic estimations proximal to the prostheses, and trifilar pendulums can measure moments of inertia with <1% error. The running experiments provided the first 3D kinetic descriptions of ILEA running. The prosthetic limb typically generated lower peak kinetic parameters and 50% lower total mechanical work than the intact and control limbs, indicating a greater reliance on the intact limb. To counter the prosthetic limb deficiencies, ILEA increased stride frequencies compared to control subjects. Additionally, the prosthetic limb demonstrated prolonged periods of anterior ground reaction force to increase propulsive impulse and prolonged hip stance phase extension moments that generated increased hip concentric work. The data indicated that ILEA wearing RSPs run differently than able-bodied runners and use several adaptive mechanisms to run at the same velocity and to increase running velocity. These mechanisms are discussed and future directions of research are suggested

Assessment and enhancement of lower extremity power of athletes

STUDY 1: RELIABILITY OF PERFORMANCE MEASUREMENTS DERIVED FROM GROUND REACTION FORCE DATA DURING COUNTERMOVEMENT JUMP AND INFLUENCE OF SAMPLING FREQUENCY. STUDY 2: COMPARISON OF FOUR DIFFERENT METHODS TO MEASURE POWER OUTPUT DURING THE HANG POWER CLEAN AND THE WEIGHTED JUMP SQUAT. STUDY 3: DOES PERFORMANCE OF HANG POWER CLEAN DIFFERENTIATE PERFORMANCE OF JUMPING, SPRINTING, AND CHANGING OF DIRECTION? STUDY 4: COMPARISON OF WEIGHTED JUMP SQUAT TRAINING WITH AND WITHOUT ECCENTRIC BRAKING

Biomechanical Spectrum of Human Sport Performance

Writing or managing a scientific book, as it is known today, depends on a series of major activities, such as regrouping researchers, reviewing chapters, informing and exchanging with contributors, and at the very least, motivating them to achieve the objective of publication. The idea of this book arose from many years of work in biomechanics, health disease, and rehabilitation. Through exchanges with authors from several countries, we learned much from each other, and we decided with the publisher to transfer this knowledge to readers interested in the current understanding of the impact of biomechanics in the analysis of movement and its optimization. The main objective is to provide some interesting articles that show the scope of biomechanical analysis and technologies in human behavior tasks. Engineers, researchers, and students from biomedical engineering and health sciences, as well as industrial professionals, can benefit from this compendium of knowledge about biomechanics applied to the human body

Aerospace medicine and biology. A continuing bibliography with indexes, supplement 195

This bibliography lists 148 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1979

A Biomechanical Analysis of Back Squats: Motion Capture, Electromyography, and Musculoskeletal Modeling

Previous literature evaluating maximal back squats have failed to identify key components of the study decisions and procedures that would allow for duplication. Firstly, the existence of a sticking region in maximally weighted resistance exercises is frequently discussed and has been described as a force-reduced transition phase between an acceleration phase and a strength phase of a lift. However, the etiology has yet to be agreed upon. Second, Electromyography (EMG) is frequently used to assess muscle activations. However, no best practice for EMG normalization has been proposed. Two methods are commonly implemented for normalizing EMG: a maximum voluntary isometric contraction (MVIC) and a dynamic maximum during the task being performed (DMVC). Finally, musculoskeletal modeling software has been increasingly utilized to evaluate muscle forces during weighted back squats. The quality of analyses of muscle forces, excitation, etc. are dependent upon inverse kinematics (IK). However, the methods used when examining IKs have also been short on details making duplication impossible. This dissertation is in a multiple-article (n=3) format. The first two studies are published in refereed journals. These studies 1) determined the effects of load on lower extremity biomechanics during back squats, 2) examined the influence of normalization method on rectus femoris, vastus medialis, and biceps femoris activations during back squats, and 3) compared different inverse kinematic strategies for calculating hip, knee, ankle, and foot kinematics utilized in modeling of the back squat. For all studies, participants performed the NSCA’s one-repetition maximum (1RM) testing protocol. Three-dimensional motion capture (trunk, pelvis, and lower extremity), force dynamometry (force plates), and EMG were recorded during all squats. The results of these studies found 1) vertical acceleration was a better discriminative measure than velocity for identifying the sticking region and there is a clear transition from knee to hip dominance for successful maximal squats, 2) the DMVC was more reliable and less variable than MVIC for normalizing EMG, and 3) creating a weld constraint between the foot and the floor results in the most closely matched foot kinematics to the DK results of the methods assessed. These results indicate that 1) submaximum squats performed at increased velocities can provide similar moments at the ankle and knee, but not hip, as maximal loads, 2) significant emphasis on hip strength is necessary for heavy back squats, 3) normalization to DMVC is the superior method for weighted exercises, and 4) while the Weld model IKs most closely matched the foot DK results, the untenable ankle kinematics the Weld model produced demonstrated it might be the superior choice for modeling foot IKs, but not ankle IKs in maximally weighted back squats

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 349)

This bibliography lists 149 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during April, 1991. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance