Tesi sul tema "Biomechanical"

Human psychophysiology forms mutually agreed unity where targeted development of one of the components can ensure the development of the other. Mass character and attractiveness of physical culture and sports as leisure components make urgent the task to develop intellectual abilities. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34847

Goldmann Applanation Tonometry (GAT) is the recognised ‘Gold Standard’ tonometer. However this status is refuted by eminent authors. These contradictory views have driven the initial goal to assess, from first principles, the evolution of GAT and to experimentally evaluate its utility and corrections. Subsequently, an important caveat became the evaluation of Corneal Hysteresis and Corneal Resistance Factor. Chapter 1. Biomechanical building blocks are defined and constitutive principles incorporated into continuum modelling. The Imbert-Fick construct is re-interpreted a simple biomechanical model. GAT corrections are also appraised within a continuum framework; CCT, geometry and stiffness. These principles enable evaluation of alternative tonometer theory and the evolving biomechanical markers, Corneal Hysteresis (ORA-CH) and Corneal Resistance Factor (ORA-CRF). Chapter 2 appraises corneal biomechanical markers, CCT, curvature, ORA-CH and ORA-CRF in 91 normal eyes and the impact these have on three tonometers: GAT, Tonopen and Ocular Response Analyser (ORA). Tonopen was the sole tonometer not affected by biomechanics. CCT was confirmed the sole measurable parameter affecting GAT. ORA did not demonstrate improved utility. ORA-CH and ORA-CRF do not appear robust biomechanical measures. Chapter 3 assessed agreement between GAT, the ORA measures and Tonopen. Tonopen is found to measure highest and raises the question should a development goal emphasise GAT agreement or improvement? Chapter 4 assessed repeatability of the three tonometers and biomechanical measures keratometry, pachymetry, ORA-CH and ORA-CRF on 35 eyes. Coefficients of Repeatability (CoR) of all tonometers are wide. Effects assessed in Chapter 5 may be masked by general noise. ORA does not appear to enhance utility over GAT. Isolation of corneal shape change via Orthokeratology (Chapter 5) demonstrate ORACH and ORA-CRF reflect, predominantly, a response to corneal flattening. It is proposed they do not significantly reflect corneal biomechanics. After reviewing models for tear forces (Chapter 6), a refined mathematical model is presented. Tear bridge attraction is minimal and cannot explain under-estimation of IOP by GAT in thin corneas. CCT corrections and the Imbert-Fick rules are incompatible. Chapter 7 summarises findings. The supremacy of GAT is likely to remain for some time, reflecting the sheer magnitude of overturning 60 years of convention, historical precedent, expert opinion as well as the logistical and educational difficulties of redefining standards and statistical norms.

Due to recent advances in aquatic research, technology, and facilities, many modes of aquatic therapy now exist. These aquatic modes assist individuals (e.g., osteoarthritis patients) in the performance of activities that may be too difficult to complete on land. However, the biomechanical requirements of each aquatic therapy mode may elicit different physiological and functional responses. Therefore, the purpose of this thesis was to: (a) provide a review of the physiological and biomechanical differences between aquatic and land based exercises, and (b) examine the acute effects of underwater and land treadmill exercise on oxygen consumption (VO2), rating of perceived exertion (RPE), perceived pain, mobility, and gait kinematics for patients with osteoarthritis (OA). Methods consisted of the retrieval of experimental studies examining the physiological and biomechanical effects of deep water running (DWR), shallow water running (SWR), water calisthenics, and underwater treadmill therapy. The methods also examined the physiological and biomechanical effects on 19 participants during and after three consecutive exercise sessions on an underwater treadmill and on a land-based treadmill. Based on the studies reviewed, when compared to a similar land-based mode, VO2 values are lower during both DWR and SWR, but can be higher during water calisthenics and underwater treadmill exercise. RPE responses during DWR are similar during max effort, and stride frequency and stride length are both lower in all four aquatic modes than on land. Pain levels are no different between most water calisthenics, and most studies reported improvements in mobility after aquatic therapy, but no difference between the aquatic and land-based modes. The OA participants achieved VO2 values that were not different between conditions during moderate intensities, but were 37% greater during low intensity exercise on land than in water (p = 0.001). Perceived pain and Time Up & Go scores were 140% and 240% greater, respectively, for land than underwater treadmill exercise (p = 0.01). Patients diagnosed with OA may walk on an underwater treadmill at a moderate intensity with less pain and equivalent energy expenditures compared to walking on a land-based treadmill.

Background Right ventricular (RV) diastolic function has been associated with outcomes for patients with pulmonary hypertension; however, the relationship between biomechanics and hemodynamics in the right ventricle has not been studied. Methods and Results Rat models of RV pressure overload were obtained via pulmonary artery banding (PAB; control, n=7; PAB, n=5). At 3 weeks after banding, RV hemodynamics were measured using a conductance catheter. Biaxial mechanical properties of the RV free wall myocardium were obtained to extrapolate longitudinal and circumferential elastic modulus in low and high strain regions (E-1 and E-2, respectively). Hemodynamic analysis revealed significantly increased end-diastolic elastance (E-ed) in PAB (control: 55.1 mm Hg/mL [interquartile range: 44.785.4 mm Hg/mL]; PAB: 146.6 mm Hg/mL [interquartile range: 105.8155.0 mm Hg/mL]; P=0.010). Longitudinal E1 was increased in PAB (control: 7.2 kPa [interquartile range: 6.718.1 kPa]; PAB: 34.2 kPa [interquartile range: 18.144.6 kPa]; P=0.018), whereas there were no significant changes in longitudinal E-2 or circumferential E-1 and E-2. Last, wall stress was calculated from hemodynamic data by modeling the right ventricle as a sphere: (stress = Pressure x radius/2 x thickness Conclusions RV pressure overload in PAB rats resulted in an increase in diastolic myocardial stiffness reflected both hemodynamically, by an increase in E-ed, and biomechanically, by an increase in longitudinal E-1. Modest increases in tissue biomechanical stiffness are associated with large increases in E-ed. Hemodynamic measurements of RV diastolic function can be used to predict biomechanical changes in the myocardium.

This thesis analyzes the wrist joint of the human hand by using a realistic threedimensional wrist model. Load distributions among carpal bones, forces on ligaments and joints were examined by using three-dimensional model. Wrist injuries and required surgical operations were examined with the model. The most crucial point of the study was that, using three-dimensional model of the wrist, hand surgeons would be able to predict results of surgical operation. Surgery planning may be done and mechanical results may be Evaluated on the wrist model.

Humans show stunning performance on a variety of manipulation tasks. However, little is known about the computation that the human brain performs to accomplish these tasks. Recently, anatomically correct tendon-driven models of the human hand have been developed, but controlling them remains an issue. In this thesis, we present a computationally efficient feedback controller, capable of dealing with the complexity of these models. We demonstrate its abilities by successfully performing tracking and reaching tasks for an elaborated model of the human index finger. The controller, called One-Step-Ahead controller, is designed in a hierarchical fashion, with the high-level controller determining the desired trajectory and the low-level controller transforming it into muscle activations by solving a constrained linear least squares problem. It was proposed to use equilibrium controls as a feedforward command, and learn the controller's parameters online by stabilizing the plant at various configurations. The conducted experiments suggest the feasibility of the proposed learning approach for the index finger model.

Parkinson's disease is a chronic neurological disorder affecting hundreds of thousands of Americans. The current best practice for assessment of this disease is a clinical examination and subjective rating using the Unified Parkinson's Disease Rating Scale. Such ratings are coarse scaled, subject to rater bias, and costly. Instruments which provide objective measurements of disease state can eliminate rater bias, provide repeatable data, and increase the frequency and responsiveness of subject assessments, expediting the validation of new therapies and treatments. This thesis describes the design and implementation of a battery of bio-mechanical devices suitable for clinical and in home use, including descriptions of the instruments and the functionality of the data acquisition software, as well as the overall system used for data collection. A data analysis algorithm is fully described, and descriptive statistics of pilot data from twenty two subjects are reported. These statistics show promising correlations of time duration metrics with the motor subsection of the UPDRS, as well as good responsiveness to dopaminergic intervention. Data also suggests that these devices have an advantage over previously described devices in the ability to record the full range of motion in standard assessment tasks, thereby providing additional metrics related to hesitations and halts in prescribed movements.

The anterior cruciate ligament (ACL) is one of four major intra-articular knee ligaments and plays a key role in knee stability. Rupture of the ACL is one of the most common and debilitating sport-related knee injuries. Most ACL ruptures do not involve direct collisions, but occur during landing, cutting, and pivoting tasks common to sports such as soccer, basketball, and netball. Rates of ACL rupture in young people have increased enormously in Australia over the past two decades. Generally, ACL ruptures are 3.5-4 times more frequent in female compared to male athletes. Among females, those aged 15-19 years are at highest risk of ACL rupture being ~4 times more likely to sustain injury than their pre-pubertal counterparts. Analysis of video footage of ACL injury events, cadaveric experiments, and biomechanical studies has yielded a consensus that external knee loads applied in three planes of motion (i.e., sagittal, frontal, and transverse) contribute to ACL rupture. Laboratory-based biomechanical studies that directly instrumented the ligament have been performed, albeit sparingly for obvious reasons of invasiveness, and show the ACL sustains substantial loading during non-injurious motor tasks. Moreover, studies using external biomechanical measures to examine ACL loading employing computational models have been limited, and have not included, and thus are insensitive to, an individual’s knee muscle activation patterns in muscle force estimates Valid models of the ACL and its loading profile have been challenging to create, and instrumented measures of ACL loading without concurrent modelling of the neuromusculoskeletal dynamics will fail to provide insight into the role of specific muscle and external loads in loading the ACL. Therefore, the mechanisms underlying ACL loading during dynamic motor tasks, through the interaction of muscles, contacting articular bodies, and other soft tissues, remain unclear. This deprives injury prevention and rehabilitation programs of personalized targets that are mechanistically linked to in vivo ACL loading. The purposes of this thesis were to develop and validate a computational model that can accurately estimate ACL force based on outputs of neuromusculoskeletal models in individuals with an intact ACL; determine ACL loading in drop-land-lateral jump task in mature females, therein examining the mechanisms that contribute to ACL loading, and; and determine effects of pubertal maturation on females’ ACL loading during a dynamic motor task considered provocative for the ACL. This thesis involved the development, validation, and application of a computational model to quantify ACL force during dynamic motor tasks. First, an ACL force model was developed using the most relevant, complete, and accessible cadaveric data from the literature. These data comprised measurements of ACL force or strain across various knee flexion angles in response to uni- and multiplanar external knee loads. Using a portion of these data, algebraic equations were fitted to well describe ACL loading in response to both uni- and multiplanar knee loading. The model was then validated using the remaining experimental data not used in model development. The validated ACL force model was then combined with an electromyography (EMG) -informed neuromusculoskeletal model to estimate ACL force developed during a standardised drop-land-lateral jump task performed by healthy females in laboratory conditions. Ninety-three females, aged 8 to 20 years, volunteered to participate in this study. All participants were recreationally active and had no history of lower limb injury or knee pain. Participants were divided into 3 groups: pre-, early/mid-, or late/post-pubertal based on Tanner’s pubertal classification system. Each participant attended a laboratory-based testing session, wherein three repeated trials of a standardized drop-land-lateral jump from a box with box height set to 30% of their lower limb length, while 3D motion capture, ground reaction forces, and surface EMG were acquired. For purposes of calibrating the EMG-informed neuromusculoskeletal model, three trials of running at a natural self-selected style (speed range from 2.8 to 3.2 m.s-1) were performed. These laboratory data were then used in a neuromusculoskeletal model to estimate ACL loading. The OpenSim modelling software was used to scale a generic anatomical model to match each participant’s gross dimensions, mass, and inertia, followed by morphometric scaling to preserve fibre and tendon operating ranges, and last adjust each muscle’s maximum isometric strength based on empirical relationships between mass and height with lower limb muscle volume. Using this scaled model, the external biomechanics (i.e., model motions and joint loading) and muscle tendon unit actuator kinematics (i.e., moment arms, lengths, and lines of action) were determined. The EMG signals were conditioned into normalized linear envelopes, which were combined with the OpenSim external biomechanics and muscle tendon unit actuator kinematics to drive a model in the Calibrated EMG-informed Neuromusculoskeletal Modelling (CEINMS) toolbox. The CEINMS was first calibrated and then run with an EMG-informed neural solution to estimate lower limb muscle and tibiofemoral contact forces. The muscle tendon unit kinematics and forces, along with the joint loads were then incorporated into the validated ACL force model to quantify ACL force. For each participant, the contribution of muscle and intersegmental loads to ACL forces were calculated across the stance phase of the drop-land-lateral jump task. Specific statistical analyses were run to address each of the research questions and encapsulated as a series of research manuscripts in the format of journal articles. The first study developed and validated a computational model that predicted the force applied to ACL in response to multiplanar knee loading that was estimated by a subject-specific neuromusculoskeletal knee model, as described above. The study demonstrated these models’ utility by applying it to a sample of motion capture data. First, a three-dimensional (3D) computational model was developed and validated using available cadaveric experimental data to estimate ACL force. The ACL force model was valid as it well predicted the cadaveric data, showing strong statistical correlation (r2=0.96 and P<0.001), minimal bias, and narrow limits of agreement. Second, by combining a neuromusculoskeletal model with the ACL force model, it was revealed that during a drop-land-lateral jump task the ACL is primarily loaded through the sagittal plane, mainly due to muscular loading. The computational model developed in study one was the first validated accessible tool that could be used to develop and test knee ACL injury prevention programs for people with normal ACL. The method used to develop this model can be extended to study the abnormal ACL upon the availability of relevant experimental data. The paper describing these results was published as Nasseri A., Khataee H., Bryant A.L., Lloyd D.G., Saxby D.J. Modelling the loading mechanics of anterior cruciate ligament, Computer Methods & Programs in Biomedicine, 184 (2020) 105098. doi: 10.1016/j.cmpb.2019.105098. Study two determined ACL force and the key muscular and biomechanical contribution to this ACL loading in a standardized drop-land-lateral jump task performed by sexually mature young females. Three-dimensional whole-body kinematics, ground reaction forces, and muscle activation patterns from eight lower limb muscles were collected during dynamic tasks performed by healthy females (n=24), all who were recreationally active. Collected data were used to model the external biomechanics, muscle-tendon unit kinematics, and muscle activation patterns using established biomechanical modelling software packages (i.e., OpenSim and MotoNMS). These biomechanical and electromyographic data were then used to calculate the lower limb muscle, joint contact and the ACL forces through an EMG-informed neural solution combined with a validated ACL force model. Peak ACL force (2.3 ± 0.5 BW) was observed to occur at 14% of the stance phase during the drop-land-lateral jump task. The ACL force was primarily developed through the sagittal plane, and muscles were the dominant source of ACL loading. The main ACL muscular antagonists were the gastrocnemii and quadriceps, while the hamstrings were the main ACL agonists. Our results highlighted the important role of gastrocnemius in ACL loading, which could be considered more prominently in ACL injury prevention and rehabilitation programmes. The paper describing these results is accepted for publication as Nasseri A., Lloyd D.G., Bryant A.L., Headrick J., Sayer T.A., Saxby D.J. Mechanism of anterior cruciate ligament loading during dynamic motor tasks. Medicine and Science in Sports and Exercise. Study three determined and compared ACL loading during a drop-land-lateral jump task in females across three pubertal stages of maturation. Further, the relative contributions to ACL force from three planes of motion (sagittal, frontal, and transverse) were compared. In this, sixty-two participants were divided into pre-pubertal (n=19), early/mid-pubertal (n=19) or late/post-pubertal (n=24) groups based on Tanner’s pubertal classification system. Each participant completed a biomechanical testing session wherein we collected three-dimensional body motion, ground reaction forces, and EMG during drop-land-lateral jump task. Using these data, the aforementioned ACL force and neuromusculoskeletal knee model was used to assess ACL loading and the key contributions to this loading. To analyse the ACL force in a continuous manner, statistical parametric mapping (SPM) analysis was used. SPM ANOVA and post-hoc t-tests were used to compare total ACL force and contributors to this force over the stance phase of the drop-land-lateral jump task between three groups of females across maturation. Compared to pre- and early/mid-pubertal, females in late/post pubertal group showed significantly higher ACL force during a large percentage of the stance phase, which encompassed the peak ACL forces. The forces developed through sagittal and transverse planes were significantly higher in late/post-pubertal group compared to the two other groups over large percentages of the stance phase. The contribution of the frontal plane mechanisms to ACL force was not significantly different across sexual maturation, while the pre- and early/mid-pubertal groups were not significantly different for any of the outcome measures. The larger ACL forces observed in late/post-puberty group (14-20 years) may partially explain the higher rate of ACL injury in females aged 15-19 years in the last decades. In addition, it has been shown that ACL growth plateaus at the age of 10, prior to full sexual maturation and cessation of growth in stature. Thus, females in late/post pubertal group are potentially heavier, have similar sized ACL, but with greater ACL forces compared to their less sexually mature counterparts. These reasons together could be the foundation, at least in part, for the higher ACL forces observed in this group. The manuscript describing these results is under review as Nasseri A., Lloyd D.G., Minahan C., Sayer T.A., Paterson K., Vertullo C.J., Bryant A.L, Saxby D.J. Effects of pubertal maturation on anterior cruciate ligament forces during a landing task in females. American Journal of Sports Medicine. In conclusion, a computational ACL force model was developed and validated that provided a platform for integration of external biomechanics, muscle and joint contact forces to calculate in vivo ACL force. This ACL force model enabled examination of the ACL loading mechanism by exploring the main muscular and biomechanical contributions to ACL loading; and the effects of pubertal maturation on ACL loading in females. The variability in the magnitude and contributions to ACL force across a wide age range of participants suggest estimation of ACL force is necessary to understand the potential ACL injury mechanisms and design ACL injury prevention programs, rather than relying on external biomechanics that are proposed as surrogates of ACL injury.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School Allied Health Sciences
Griffith Health
Full Text

L’articolazione dell'anca è un'articolazione sinoviale sferica che costituisce la connessione primaria tra gli arti inferiori e lo scheletro della parte superiore del corpo. Durante le attività quotidiane di routine, carichi anormali ripetuti sull'anca possono portare alla danneggiamento della cartilagine articolare e conseguentemente , all’osteoartrite (OA). L'OA dell'anca è una condizione muscolo-scheletrica cronica e progressiva, il cui trattamento per i pazienti severi è l'artroplastica totale dell'anca (THA). Il centro dell'articolazione dell'anca (HJC) ha grande importanza nell’analisi della biomeccanica dell’anca, così come il suo spostamento, che puo’ essere dovuto a patologie, come OA, o alla chirurgia, THA. Per valutare la biomeccanica del bacino in questa tesi sono stati implementati un modello muscoloscheletrico (NMS) personalizzato statistical shape e modelli ad elementi finiti (FE) di un paziente con grave OA mono-laterale dell'anca. Viene discussa l'accuratezza relativamente al modello scalato generico nella predizione delle grandezze biomeccaniche piu’ importanti, durante la deambulazione. Attraverso i modelli FE, è stato studiato l'effetto di una cattiva stima e/o dello spostamento del centro dell'articolazione dell'anca nelle direzioni antero-posteriore, mediolaterale o infero-superiore per valutare lo stato di sollecitazione della pelvi. Infine sono presentati i risultati di un approccio multiscala integrato, per valutare le caratteristiche biomeccaniche del suddetto paziente, passando dalla modellazione NMS, all’analisi del modello FE della pelvi, per effettuare un’analisi comparativa dell’arto osteoartritico con il modello dall’arto controlaterale prima dell’intervento e dopo lo stesso

Degeneration and age affect the biomechanics of the intervertebral disc, by reducing its stiffness, flexibility and shock absorption capacities against daily movement and spinal load. The biomechanical characterization of intervertebral discs is achieved by conducting mechanical testing to vertebra-disc-vertebra segments and applying axial, shear, bend and torsion loads, statically or dynamically, with load magnitudes corresponding to the physiological range. However, traditional testing does not give a view of the load and deformation states of the disc components: nucleus pulposus, annulus fibrosus and endplate. Thus, the internal state of stress and strains of the disc can only be predicted by numerical methods, one of which is the finite element method. The objective of this thesis was, to study the biomechanics of degenerated intervertebral discs to load conditions in compression, bending and torsion, by using mechanical testing and a finite element model of disc degeneration, based on magnetic resonance imaging (MRI). Therefore, lumbar discs obtained from cadavers corresponding to spinal levels L2-L3 and L4-L5 with mild to severe degeneration were used. Intervertebral osteochondrosis and spondylosis deformans were identified, being the disc space collapse, the most striking feature. Next, all discs were tested to static and dynamic load conditions, the results gained corresponded to the disc stiffness (in compression, bending and torsion), stress relaxation and dynamic response. Of these, the stiffness response was used to validate the disc model. The testing results suggest that discs with advanced degeneration over discs with mild degeneration are, less rigid in compression, less stiffer under bending and torsion, showed less radial bulge, and reduce their viscoelastic and damping properties. This study shows that degeneration has an impact on the disc biomechanical properties which can jeopardize normal functionality. Development of one finite element model of disc degeneration started by choosing a MRI of a L2-L3 disc. Segmentation of vertebra bone and disc materials followed, and were based on pixel brightness and radiology fundamentals, then a finite element mesh was created to account for the disc irregular shape. The disc materials were modeled as hyperelastic and the bone materials were modeled as orthotropic and isotropic. Adjustment of material properties was based on integrity of the annulus fibrosus, giving a stiffness value matching that of a mild degeneration disc. Then, validation of the model was performed, and included a study of the distributions of stress and strain under loads of compression, bending and torsion. The results from all load simulations show that the disc undergoes large deformations. In contrast, the vertebrae are subjected to higher stress but with negligible deformations. In compression, the model predicted formation of symmetrical disc bulge which agree with the testing behavior. The nucleus pulposus showed to be the principal load carrier with negative principal stresses and strains. In bending and torsion, the annulus fibrosus showed to be the principal load carrier with large symmetrical principal strains and stresses for the former loading and large shearing for the latter. The study showed the importance of soft tissue deformation, mostly noticed in advanced degeneration. In contrast, the higher stresses in the vertebra over those of the intervertebral disc showed the relevance of bone predisposition to fracture. Such kind of studies, should contribute to the understanding of the biomechanics of the intervertebral disc.
La degeneración y edad afectan la biomecánica del disco intervertebral, reduciendo la capacidad de rigidez, flexibilidad y atenuación de impactos, contra el movimiento y carga del raquis. La caracterización biomecánica del disco se realiza con ensayos mecánicos a segmentos de vértebra-disco-vértebra y aplicando cargas axiales, cortantes, flexión y torsión, estáticas ó dinámicas, con magnitudes de carga según el intervalo fisiológico. Sin embargo, las pruebas tradicionales no dan una visión de los estados de carga y deformación de los componentes del disco: núcleo pulposo, anillo fibroso y placa terminal. Por lo tanto, el estado interno de esfuerzos y deformaciones del disco, solo puede ser predicho con métodos numéricos, uno de los cuales es el método de elemento finito. El objetivo de esta tesis fue, estudiar la biomecánica de discos intervertebrales degenerados a las condiciones de carga en compresión, flexión y torsión, mediante el uso de ensayos mecánicos y de un modelo de elementos finitos de la degeneración de disco, basado en imágenes con resonancia magnética (MRI). Por lo tanto, se usaron discos lumbares L2-L3 y L4-L5 obtenidos de cadáveres, con degeneración leve a severa. Se identificó osteocondrosis intervertebral y espondilosis deformante, siendo el colapso del espacio intervertebral el aspecto más relevante. Luego, todos los discos fueron ensayados a condiciones de carga estática y dinámica, y los resultados correspondieron a la rigidez del disco (a compresión, flexión y torsión), a la relajación de tensiones y a la respuesta dinámica. De éstos, la rigidez fue usada para validar el modelo de disco. Los resultados de los ensayos sugieren que los discos con degeneración avanzada sobre aquellos con degeneración leve son, menos rigidos a compresión, menos rigidos a flexión y torsión, presentan menor protuberancia radial, y reducen sus propiedades viscoelásticas y de amortiguamiento. El estudio muestra que la degeneración impacta las propiedades biomecánicas del disco, poniendo en riesgo la funcionalidad normal. El desarollo de un modelo de elementos finitos de la degeneración de disco inició eligiendo una secuencia de resonancia magnética de un disco L2-L3. La segmentación de los materiales del disco y de las vértebras se realizó basado en intensidad de brillo del pixel y en fundamentos de radiología, y se creó una malla de elementos finitos correspondiente a la forma irregular del disco. Los materiales del disco se modelaron como hiperelásticos y los tejidos óseos se modelaron como materiales ortotrópicos e isotrópicos. El ajuste de propiedades de los materiales fue basado en la integridad del anillo fibroso, y dio una rigidez correspondiente a la de un disco con degeneración leve. Luego, se realizó la validación del modelo, e incluyó un estudio de las distribuciones de esfuerzo y deformación a las condiciones de carga en compresión, flexión y torsión. Los resultados de todas las simulaciones de carga mostraron que el disco es sometido a grandes deformaciones. En contraste, las vértebras fueron sometidas a mayores esfuerzos pero con deformaciones insignificantes. En compresión, el modelo predijo la formación de una protuberancia radial simétrica, en concordancia con la experimentación. El núcleo pulposo mostró ser el portador principal de carga, con tensiones y deformaciones principales negativas. En flexión y torsión, el anillo fibroso mostró ser el portador principal de carga, con grandes deformaciones y tensiones principales simétricas para la primera carga, y con grandes tensiones cortantes para la segunda carga. El estudio mostró la importancia de las deformaciones de los tejidos blandos, principalmente notados en la degeneración avanzada. Por el contrario, las tensiones mayores en los cuerpos vertebrales sobre aquellas del disco intervertebral mostraron la relevancia de la predisposición a las fracturas óseas. Este tipo de estudio debe contribuir a la comprensión de la biomecánica del disco intervertebral.

Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第17557号
工博第3716号
新制||工||1566(附属図書館)
30323
京都大学大学院工学研究科マイクロエンジニアリング専攻
(主査)教授 安達 泰治, 教授 楠見 明弘, 准教授 井上 康博, 教授 琵琶 志朗
学位規則第4条第1項該当

Biomechanical testing has been the cornerstone of sports bra research to date and the quantification of breast kinematics during exercise has received increasing interest. However, comparatively little research has been published regarding the development of biomechanical testing methodology and how this testing may inform the development of sports bra design. Thus, the overall research aim was the 'Development and application of methods used in the biomechanical assessment of sports bra performance with the end goal of better biomechanical tools for use in the sports bra design process'. Breast kinematics are typically measured relative to the torso, therefore, it is necessary to track both torso and breast motion. The absence of a universally accepted torso tracking model, and information regarding the sensitivity of breast kinematics to the selected torso model were identified as limitations to the existing research. The seven marker torso tracking model presented is the first to be specifically developed for analysing relative breast motion during activities such as treadmill running and is recommended to be implemented in future sports bra research. The torso segment used to calculate relative breast kinematics is assumed to be rigid, however, breast movement resulting from respiration has been reported for a static condition. The effect of breathing on breast kinematics during treadmill running was investigated. Significant differences were observed in the breast kinematics between breathing and non-breathing conditions, notably in the superior-inferior direction; however, they could not definitively be directly linked to breathing since significant differences in running gait were also observed. The results do suggest that increasing the number of gait cycles analysed may reduce any effects of breathing on breast kinematics due to phase-locking, the synchronisation of breathing with running locomotion. Analysing breast kinematics over 30 gait cycles may help minimise any potential effects of phase-locking across all commonly used phase-locking ratios. Further understanding of breast motion and whether markers placed on the bra represent the underlying breast were identified as pertinent to advancing biomechanical assessment of sports bra performance. Motion between the breast and bra (either during an initial bedding in phase or steady state running) has yet to be explored within the existing literature and is assumed to be negligible for a correctly fitted bra. A settling in period of ~30 seconds between the breast and bra was found to occur during the initial phase of treadmill running. Whilst the study is recognised to be exploratory in nature, the findings suggest future breast kinematic study should consider the possibility of a settling in effect. Therefore, experimental protocols may benefit from including a short period of activity after the subject has changed into the bra to help eliminate any settling in effect prior to data capture or application of over bra markers. The results also suggest that motion occurs between the breast and bra irrespective of bra size and that over bra markers underestimate superior-inferior (S-I) breast displacement and anterior-posterior (A-P) displacement at the upper breast. Markers positioned over the bra were found to be less sensitive to variation in A-P and S-I displacement in different regions of the breast. However, use of under bra markers is limited by current motion capture technology and until advances in technology are made the use of over bra markers remains current best practice. Future studies are recommended to state whether breast markers were located over or under the bra and recognise that over bra markers represent bra motion. Bra strap stiffness was identified as a potentially important factor in sports bra performance. The effect was investigated using a modified bra with removable strap sections of three differing stiffness. Bra strap mechanical properties were characterised using a specifically developed tensile testing protocol. Sports bra performance during treadmill running was assessed using biomechanical and perceptual measures. Increasing bra strap stiffness was found to improve sports bra performance with respect to bra kinematics (primarily in the superior-interior direction) and subjective perception ratings (in particular the perception of support), suggesting strap stiffness may have an important role to play in bra design.

Saphenous veins are widely used as graft material in coronary artery bypass surgery. Biomechanical testing may help identify veins with the optimum chance of longevity. In this thesis, the author has constructed an experimental apparatus to measure circumferential and axial stress-strain data for such arteries and veins. Three different experimental techniques were used to obtain the dimensions of the vessels during pressure-diameter tests; the traditional method of photographic and direct measurement of the external dimensions along with the assumption of incompressibility to approximate inner dimensions; second the use of intravascular ultrasound to obtain the inner and outer dimensions of the vessels; and third the use of intravascular ultrasound for internal dimensions and photography for the outer dimensions. Three forms of mathematical expression were fitted to the circumferential and axial stress-strain data. The sensitivity of the resulting material parameters was investigated with regard to conversion and reference data variations, and data from repeated experiments, experiments fitting more than one axial strain, and experiments testing the variation in elastic properties were compared. The combination of the ultrasound experimental technique and exponential form of mathematical expression was found to be the most robust. Using this combination, a significant difference between material parameters of pig arteries and human saphenous veins was found . While the data indicate that material parameters of healthy and diseased veins may also differ significantly, the number of healthy veins in this study was not sufficient to be conclusive.

Flatwater sprint kayaking performance can be assessed through the analyses of average boat velocity a paddler can produce, which has been shown to be directly linked to the levels of force production. Furthermore kayaking has been the subject of substantial level of investigation, within which research has identified that the evolution of equipment and resultantly technique has a direct effect on performance. The focus of the previous research has revolved around the upper limbs, with the trunk and lower limbs viewed as an inconsequential base around which the upper limbs move. Therefore the current thesis attempts to identify the application of the entire body during kayak paddling and clarify the importance of trunk and leg contributions to performance. A notational analysis of technique was conducted comparing novice, national and international level paddlers. International paddlers displayed significantly (P < 0.05) lower race and stroke times, as a result of significantly higher stroke rates. In addition aspects of technique were ranked from zero to five from which international paddlers displayed significantly (P < 0.05) greater trunk rotation, leg motion, stroke width, and forward reach. These findings were supplemented by the international paddlers entering the paddle significantly closer to the centre line of the kayak, while holding a fixed forward lean position of the trunk. These findings provide important factors within technique that can be identified visually; however further investigation was required to identify their importance in the development of force and kayak velocity. Consequently the development of an on-water analysis system was required to ensure a comprehensive analysis of technique. This was conducted through the combination of kinetic, 3-demensional kinematic, electromyographic and electrogoniometric analysis methods, using subjects (n = 8) with international experience. Subjects were prepared with passive surface electrodes and joint markers, and completed the testing protocol following completion of informed consent and a medical questionnaire. Statistical analysis identified that a moderate positive significant predictive relationship (R1= 0.529, P<0.05) existed between peak force and mean velocity during the left paddle stroke. Separating the trunk into thoracic and lumbar regions revealed a significant negative predictive relationship (P < 0.05) between velocity and range of lumbar spine rotation. Further significant (P < 0.05) findings were identified between activation levels of the rectus abdominus, external obliques and the production of force and velocity. The combination of these findings indicated that the lower trunk acted as a strong stable base against which force was produced increasing average kayak velocity. The activation of the left rectus femoris displayed significant relationships (P < 0.05) with force and velocity during both left and right strokes; indicating that the legs act as braces against which the force is transferred to the kayak. These findings reinforced those identified during the notational analysis, indicating that the legs and trunk play a fundamental role within the development of kayak velocity and therefore performance. It is therefore important that paddlers ensure that the musculature of the trunk and legs are used during performance and that the vital axial rotations occurring in the spine are produced in the thoracic region.

A biomechanical model of the glenohumeral joint has been developed to investigate muscle and joint loading during real life three-dimensional activities. Based on a rigid body mechanics approach, the model incorporates algorithms to correct for curved muscle paths and bone geometry, providing realistic muscle orientation over a wide range of limb positions. An optimization routine has been incorporated, minimizing overall maximum muscle stress in the 26 individual muscle elements considered. The model utilizes anatomical muscle and bone data, subject anthropometric data, kinematics measured using a 6 camera Vicon motion analysis system and hand loading measured using a force-plate and mobile six-component strain gauged force transducer developed for this project. Model stability and sensitivity to input data uncertainties have been investigated. Data used for this was actual subject activity data. Random uncertainties of a known statistical distribution were generated using a Monte Carlo data perturbation technique and superimposed on the subject data. No model instability or unacceptable error magnification was demonstrated in this investigation. A study of real life three-dimensional activities has been conducted using five male subjects. Normalized, averaged muscle and joint forces were calculated for each activity. Using the same five subjects, electromyographic (EMG) muscle activation was measured for the same five activities. Both surface and intra-muscular fine wire electrode techniques were used. Eight muscles including infraspinatus, subscapularis and supraspinatus were instrumented. The resulting EMG data was normalized and averaged for each activity. Muscle activation appears in good agreement with published EMG and our own EMG study. Overall joint compressive and shear forces of up to 7 and 2 times body weight respectively have been calculated. Results of the study indicate glenohumeral joint forces for athletic activities can be as high as 7 times those forces previously predicted in other studies for simple abduction and flexion.

Introduction: As fractures of the supraorbital region are far less common than midfacial or orbital fractures, a study was initiated to investigate whether fist blows could lead to fractures similar to those often seen in the midface. Methods: A detailed skull model and an impactor resembling a fist were created and a fist blow to the supraorbital region was simulated. A transient finite element analysis was carried out to calculate von Mises stresses, peak force, and impact time. Results: Within the contact zone of skull and impactor critical stress values could be seen which lay at the lower yield border for potential fractures. A second much lower stress zone was depicted in the anterior-medial orbital roof. Conclusions: In this simulation a fist punch, which could generate distinct fractures in the midface and naso-ethmoid-orbital region, would only reach the limits of a small fracture in the supraorbital region. The reason is seen in the strong bony architecture. Much higher forces are needed to create severe trauma in the upper face which is supported by clinical findings. Finite element analysis is the method of choice to investigate the impact of trauma on the human skeleton.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (leaves 33-35).
An experiment was performed to determine the effect of crosslinking on the stiffness of collagen scaffolds. Engineered non-crosslinked and dehydrothermally crosslinked chondroitin-6-sulfate collagen scaffolds were hydrated and loaded in tension, and their mechanical properties were compared. It was found that non-crosslinked scaffolds experience an average increase in weight after hydration of 10,353%, compared to 7,265% for crosslinked scaffolds. Hyperelastic material parameters were determined by the Arruda-Boyce eight-chain model, which was fit to the experimental data. This model predicted an average number of rigid links per collagen fiber of 1.3 and 1.21 for crosslinked and non-crosslinked scaffolds, respectively. Additionally, the collagen fiber densities were found to be 2.92 x 1017 for crosslinked networks and 1.68 x 1017 for non-crosslinked networks. These results can be applied to the changes that take place in the cervix at the onset of delivery. It is hypothesized that the crosslinking between collagen fibers in the cervix breaks down during preparation for delivery, allowing more fluid to enter the extracellular matrix and weaken the tissue. By performing tension tests on cervix tissue in vivo, one can produce a theoretical fit to predict relevant collagen network parameters, which can be compared with those of non-pregnant cervical tissue to indicate the early onset of cervical ripening.
(cont.) By being able to quantitatively assess a woman's risk of early cervical ripening, it may be possible to prevent premature births associated with cervical insufficiency.
by Christina M. Bonebreak.
S.B.

Neural tube defects (NTDs) are amongst the commonest birth defects, affecting 1 in 1000 pregnancies. During neurulation, failure of neural tube closure in the low spinal region (at the posterior neuropore, PNP) results in spina bifida. Mechanical force relationships in the normally closing neural tube and in the NTD-developing neural tube were investigated through incision of the most recently closed neural tube roof, in order to eliminate tension in the closed region. After incision in wild-type embryos, immediate springing apart (re-opening) of the elevating neural folds was observed, associated with partial relaxation of the bending degree of the Dorsolateral Hinge Points (DLHP) and the Median Hinge Point (MHP) in transverse sections. When incision was performed on Zic2 mutant embryos developing spina bifida, a larger re-opening of neural folds was observed than in wild-type controls. These findings coincided with measurements of the elastic modulus of the mutant NPs using Atomic Force Microscopy, which revealed that the dorsal NP of the mutant embryos is stiffer than wild-type. Finite Element Method (FEM) modelling also showed that a larger closing force is required for a stiffer NP. Moreover, in unincised embryos, nuclei were found to be more elongated in the wild-type NP, where DLHPs are present, than in the mutant NP, where DLHPs are absent, suggesting possible roles of cell packing in DLHP formation. In conclusion, apposition of the NFs is an elastic process exogenously driven by the force field that originates from the most recently closed point. DLHP formation, however, is a partially plastic process, closely related to cell packing within the dorsal NP as an endogenous event. In Zic2 mutant embryos, a stiffer NP and the absence of cell-packing in the dorsal NP region are perhaps the main mechanical causes of spinal neurulation failure.

Lameness is a major cause of lost productivity for the pig industry. The objective of this PhD was to develop an objective motion capture method for growing pigs and assess (1) the repeatability and sensitivity of the method (2) the gait characteristics of pigs housed on different floor types and (3) gait differences in pigs with conformational deficiencies, joint disease and/or clinical lameness. Infrared camera-based motion capture was applied to three different cohorts of pigs in three experiments, including an observational study following 84 gilts from grower- to second-parity stage. 3D coordinate data of reflective skin markers attached to head, neck, trunk and leg anatomical landmarks were collected. Temporal (time), linear (displacement) and angular (joint angles) kinematic gait parameters were calculated. Repeatability of the method varied with amount of overlying tissue and/or prominence of anatomical landmarks used for marker placement, but not necessarily with walking speed. Gait development of pigs reared on fully-slatted, partly-slatted or deep straw-bedded floors was not different. Lameness detection and evaluation was possible using relative linear and temporal kinematics. The within-stride trajectory of head and pelvic regions during walking differentiated pigs with front and multi-leg lameness from normal pigs, respectively. The ipsilateral swing-to-stance time ratio detected lameness in hind legs, but was not affected during multi-leg lameness. The frequency and magnitude of irregular steps was increased in lame pigs and in pigs with subclinical joint lesions of osteochondrosis diagnosed post slaughter. Step irregularity (as reflected in the step-to-stride length ratio) was also predictive of impending lameness. The step-to-stride length ratio is a dimensionless and ideal parameter to monitor pigs of different age and size, moving at a self-chosen walking speed. Flexion asymmetry and joint flexion patterns were indicative of locomotor problems in some cases. Gait analysis therefore offers potential for automated prediction and early detection of lameness.

Globally, 1% of the population is affected by arthritis of the foot and ankle. Total ankle replacement (TAR) was developed as an alternative to fusion to treat end-stage arthritis, however failure rates are relatively high and are often related to bony damage. The purpose of this PhD was to develop a finite element (FE) model of a TAR to examine the risk of bone failure, and how this is affected by component alignment. An experimental model of a TAR implanted into synthetic bone was first created as a means to validate an initial FE model under known conditions. Location and size of the plastic deformation were compared and good agreement was found. A FE model of the natural ankle was then created from cryosectional images obtained from the Visible Human Project®. It was analysed in the natural state and after virtual implantation with a TAR. Both the cortical stiffness and the surgical positioning of the TAR were varied to represent relevant ranges seen clinically. In the TAR models, the location of the highest stress was shifted from the region of high strength to a region of lower strength of bone. The maximum von Mises stress on the cancellous bone was primarily affected by the stiffness of cortical structure and the distance between the stem and the outer surface of the cancellous bone. In some misalignment cases, the yield stress for cancellous bone was likely to be exceeded under loads representing standing. The results indicated that the quality of the bone and the thickness of the trabecular bone surrounding the TAR stem are important factors in governing the risk of bony failure following TAR, and should be taken into account clinically. The methods developed in this thesis can now be extended to examine other TAR designs and surgical approaches.

Motor vehicle collisions can result in life threatening liver injuries. Dummies are utilized to study injury in motor vehicle collisions; however, no crash test dummies are currently equipped to represent individual solid organs. This has increased the use of finite element models to help reduce these injuries; however, accurate material models need to be established to have accurate injury assessment using these models. This thesis presents a total of 4 studies that explore the biomechanical response of liver. The research on bovine liver is geared to understanding whether or not liver tissue can be frozen prior to testing and what environmental temperature the liver should be tested at. The first study utilized two bovine livers that were each divided in half and one half was tested at 75°F while the other half was tested at 98°F. A total of 24 tensile failure tests were performed on the parenchyma. It was determined that there were no statically significant differences between failure stresses and strains between the testing temperatures. To test the effects of freezing, tensile tests were performed on the parenchyma of a single bovine liver that was divided in half. One half was frozen and then thawed prior to tensile testing while the other was tested fresh. It was determined that freezing reduces average failure strain by 50%. The research on human liver was geared toward understanding the rate dependence during uniaxial tension tests and unconfined compression tests. Samples were constructed of only the parenchyma. A total of 7 livers were used to create the 51 tensile specimens and a total of 6 livers were used to obtain the 36 unconfined compression specimens. For the uniaxial tensile tests, average failure stresses ranged from 40.21 to 61.02 kPa while average failure strain ranged from 24% to 34%. For the unconfined compression tests, average failure stresses ranged from -165 to -203 kPa while average failure strain ranged from -46% to -61%. It is expected that the results presented in this thesis will: 1) Help establish correct transportation and procurement methodology for soft tissue mechanical testing. 2) Provide tension and compression material response of the human liver at multiple strain rates for use as material properties and injury tolerance values to validate finite element models.
Master of Science

Running is a popular recreational and competitive sport worldwide. Despite numerous proven health benefits associated with road running, the risk of sustaining a running-related injury (RRI) is extremely high. The cause of RRI is multifactorial and the result of running many kilometres on monotonous and mechanically stiff road surfaces has been suggested to increase the risk of sustaining an injury. Interestingly, this notion may be a key driving factor for the emergence and growing interest in, trail or 'off-road’ running. Research investigating road running has been well-described, whereas the impact of regular running on natural, dynamic trail surfaces on the musculoskeletal system has yet to be fully considered. Thus, this thesis sought to understand the trail running athlete, with particular focus on elucidating the clinical, biomechanical and neuromuscular consequences of habitual running training on off-road terrain. The present thesis begins with a comprehensive review of the literature. The aim of this chapter was to briefly describe the origins of trail running, explore the theoretical driving factors behind interest in trail running, and detail the current scientific understanding of trail running and the purported implications and benefits thereof. Gaps in the existing body of knowledge were highlighted, with recommendations for necessary future research. The first study aimed to describe clinical measures of dynamic stability in well-trained trail runners and contrast this group with age- and performance-matched road runners. All runners performed three clinical assessments: the Star Excursion Balance Test (SEBT), Unilateral Bridge Hold (UBH) and Single Leg Squat (SLS). No differences were found in UBH and SEBT assessments. During the SLS task, trail runners exhibited less ankle varus and less ankle external rotation at peak knee flexion in comparison to road runners. These findings suggest that trail runners’ performance in the SLS test may represent a kinematic adaptation to habitual terrain targeted at minimising ankle joint movement during weight-bearing. Subsequently, we aimed to determine whether running biomechanics would differ between 20 habitually shod trail runners and 20 road running counterparts due to their preferred training terrain. A special focus of this chapter was to determine whether the groups of runners presented with disparate risk of sustaining a running-related injury (RRI). To evaluate this hypothesis, all runners performed barefoot and shod overground running trials on a synthetic track. Regardless of footwear condition, trail runners presented with greater step frequency, shorter ground contact time and shorter step duration. Further group differences were observed, with trail contact time and shorter step duration. Further group differences were observed, with trail runners exhibiting notably advantageous kinematics at the level of the ankle and the foot, presenting with: smaller foot strike angle, lower pronation magnitude and velocity, and lower ankle stiffness. Considering these biomechanical parameters, it was unexpected to find that trail runners experienced similar initial loading rates (ILRs) and higher ground reaction forces to road runners in response to the synthetic track. The final experimental chapter explored the notion that preferred running terrain has an influence on neuromuscular regulation of running biomechanics. To examine this, electromyography and biomechanical variables were determined using previously described protocols. Regardless of footwear condition, trail runners exhibited greater gluteus maximus, biceps femoris and peroneus longus muscle activation during terminal swing in comparison to road runners. In addition, trail runners exhibited greater tibialis anterior activation during early swing. With regards to discrete biomechanics, trail runners presented with greater lower extremity joint stability in the sagittal plane, demonstrating lower pelvic, hip and knee flexion at initial ground contact. Interestingly, similar ground reaction forces were experienced by trail and road runners on the synthetic track, suggesting that the observed muscle 'tuning’ responses to these impact forces may be managed by the differing neuromuscular responses. The outcomes of this thesis suggest that there are numerous clinical, mechanical and neuromuscular implications of habitual running training on the trail and road. Although the present thesis is the first step to understanding the demands of regular trail running on the human body, future studies using portable motion capture and inertial systems are necessary to determine the precise influence of real-time trail running on the neuromuscular system and running biomechanics. Interestingly, trail runners demonstrated several purported 'advantageous’ kinematic and spatiotemporal parameters, and exhibited differing muscle activity patterns in comparison to road runners in a controlled laboratory setting. However, trail and road runners experienced similar ILRs in response to the synthetic track. Considering the high incidence of road RRI, and that higher vertical load has been associated with chronic RRI, this finding suggests that trail and road runners could be at similar risk of developing a RRI. However, due to the disparate nature of trail and road running terrains and the multifactorial nature of RRIs, further clarity on 1) the acute and long-term effects of off-road running and 2) the injury risk profile of a trail runner, is imperative for a holistic understanding of the risks and benefits associated with participation in this sport. We recommend that the influence of trail running on the musculoskeletal system presented in this thesis be considered as a foundation for future large-scale epidemiological and prospective injury research.

The aim of this study was to provide a comprehensive analysis of key biomechanical variables in race walking through the analysis of elite athletes in both competitive and laboratory settings. Video data from two 3CCD camcorders of athletes competing over 10 km (juniors only), 20 km, and 50 km were collected at three international competitions. For the 20 km and 50 km events, multiple recordings were made to identify if kinematic changes occurred. In addition, synchronised high-speed video, electromyography and ground reaction force data were collected of 20 elite race walkers in a laboratory setting and combined to calculate joint moments, power and work. The key discriminants with regard to better performances were long step lengths and high cadences, and the contribution made by flight distance to step length (approximately 13%) was particularly important, regardless of race distance or age category. Step length ratio was a better predictor of optimum step length than absolute values and a ratio of about 70% was found in the fastest athletes. Although reductions in step length and flight distance were a major cause of decreased speed over both 20 km and 50 km, many gait variables did not alter greatly, showing that these elite athletes were able to maintain their techniques despite fatigue. The foot position ahead of the body at initial contact (approximately 20% of stature) need not be detrimental to fast walking if the athlete has the strength to overcome the potentially negative effects; instead, it can be beneficial to increase this distance in achieving a greater step length and could be a key area for women in particular to develop. The hip muscles were the main source of energy generation, with both flexors and extensors doing more positive work than any other muscle group (22.4 ± 7.1 J and 42.3 ± 10.1 J respectively), although the ankle plantarflexors also generated considerable energy before toe-off (16.4 ± 3.8 J). A hip extensor moment that occurred during late swing and early stance helped maintain forward momentum as it reduced the braking peak force and duration of the negative anteroposterior force. The knee had little involvement in energy generation because of its predominant role as a rigid lever during stance, and absorbed considerable energy during swing (–46.4 ± 9.5 J). However, its abnormal movement that was dictated by the race walking rule also had an important role in maintaining contact with the ground and reducing vertical forces so that visible loss of contact was avoided. The study was the first to analyse in such depth the biomechanics of elite male and female race walkers across all competitive distances and its results could be used to develop a technical manual for this Olympic event and greatly impact on coaching practice.

Long-term survivorship of a total knee replacement (TKR) relies on the strength of bone around the implant and its initial stability. Aseptic component loosening caused by mechanical factors is a recognised failure mode for knee prostheses. Bone resorption due to “stress-shielding” of the stiff stemmed implants will potentially lead to weakened bone strength, and presents a challenge for revision TKR surgery. The aim of this study was to develop analytical methodologies for the investigation of fixation performance of TKR, and to gain a better understanding of the prosthetic design requirements, addressing two major mechanical problems of bone remodelling and aseptic loosening. Patient-specific finite element (FE) modelling incorporated with a strain-adaptive bone remodelling theory was used to simulate bone remodelling responses of the postoperative tibial fixation. The choice of cementing technique was found to influence the remodelling behaviour; cemented fixationmodelled as a firm anchorage of the prosthesis onto the bone, was predicted to induce greater stress-shielding effect consequently leading to severe proximal bone resorption; for a fixation relying on biological attachment of bony ingrowthmodelled as a less firmly anchored boneprosthesis interface, lesser proximal bone resorption was predicted. The consideration of bone remodelling in FE simulations for fixation analyses is paramount as it influenced the risk prediction of aseptic loosening between prosthesis designs. The cement tensile stresses and bone-prosthesis interface micromotions predicted were different prior to and after bone adaptation. FE predictions of the MIS mini-keel and standard stemmed prosthesis fixations after simulating six months of bone adaptation correlated well with the RSA measurements at a similar period. A modified in-vitro technique of measuring bone-prosthesis relative micromotion was developed for relating initial stability of the cemented and cementless (press-fit) tibial prostheses fixations to late aseptic loosening. The developed computational and invitro methods should be applicable to other joint replacements.

Thesis (M.S.)--University of Tennessee Health Science Center, 2009.
Title from title page screen (viewed on October 8, 2009). Research advisor: Denis DiAngelo, Ph.D. Document formatted into pages (viii, 75 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 34-38).

[Truncated abstract] The study of biomechanical system dynamics consists of research to obtain an accurate model of biomechanical systems and to find appropriate torques or forces that reproduce motions of a biomechanical subject. In the first part of this study, specific computational models are developed to maintain relative angle constraints for 2-dimensional segmented bodies. This is motivated by the fact that there is a possibility of models of segmented bodies, moving under gravitational acceleration and joint torques, for its segments to move past the natural relative angle limits. Three models to maintain angle constraints between segments are proposed and compared. These models are: all-time angle constraints, a restoring torque in the state equations and an exponential penalty model. The models are applied to a 2-D three segment body to test the behaviour of each model when optimizing torques to minimize an objective. The optimization is run to find torques so that the end effector of the body follows the trajectory of a half circle. The result shows the behavior of each model in maintaining the angle constraints. The all-time constraints case exhibits a behaviour of not allowing torques (at a solution) which make segments move past the constraints, while the other two show a flexibility in handling the angle constraints more similar to a real biomechanical system. With three computational methods to represent the angle contraint, a workable set of initial torques for the motion of a segmented body can be obtained without causing integration failure in the ordinary differential equation (ODE) solver and without the need to use the “blind man method” that restarts the optimal control many times. ... With one layer of penalty weight balancing between trajectory compliance penalty and other optimal control objectives (minimizing torque/smoothing torque) already difficult to obtain (as explained by the L-curve phenomena), adding the second layer penalty weight for the closeness of fit for each of the body segments will further complicate the weight balancing and too much trial and error computation may be needed to get a reasonably good set of weighting values. Second order regularization is also added to the optimal control objective and the optimization has managed to obtain smoother torques for all body joints. To make the current approach more competitive with the inverse dynamic, an algorithm to speed up the computation of the optimal control is required as a potential future work.

Moment arms are important in many contexts. Various methods have been used to estimate moment arms. It has been shown that a moment arm changes as a function of joint angle and contraction state. However, besides the influence of these anatomical factors, results from recent studies suggest that the estimation of moment arm is also dependent on the methods employed. The overall goal of this thesis was to explore the interaction between the methodological and anatomical influences on moment arm and their effect on estimates of muscle-tendon forces during biomechanical modelling. The first experiment was a direct comparison between two different moment arm methods that have been previously used for the estimation of Achilles tendon moment arm. The results of this experiment revealed a significant difference in Achilles tendon moment arm length dependent on the moment arm method employed. However, besides the differences found, results from both methods were well correlated. Based on these results, methodological differences between these two methods were compared across different joint angles and contraction states in study two. Results of experiment two revealed that Achilles tendon moment arms obtained using both methods change in a similar way as a function of joint angle and contraction state. In the third experiment, results from the first two experiments were used to determine how methodological and anatomical influences on Achilles tendon moment arm would change muscle-tendon forces during the task of submaximal cycling. Results of the third experiment showed the importance of taking the method, ankle angle and contraction state dependence of Achilles tendon moment arm into account when using biomechanical modelling techniques. Together, these findings emphasis the importance of carefully considering methodological and anatomical modifiers when estimating Achilles tendon moment arm.

Sprint cross-country skiing is a physiologically and technically complex discipline, performed as a time-trial qualification race and three subsequent knock-out heats. The racing time in a single heat is 2-4 min and is comparable to other middle-distance sports. However, sprint skiing is performed in varied terrain at constantly changing intensities using multiple techniques involving the arms and the legs to various degrees. The overall objectives of the current thesis were to examine physiological and biomechanical aspects associated with sprint skiing performance in the skating technique in elite skiers: 1) while treadmill roller skiing in the laboratory (studies I-IV), 2) during sprint competitions on snow (studies IV-V) and 3) for relationships between laboratory characteristics and performance on snow (studies IV-V). Studies I-III are comparative studies in which physiological characteristics, mechanical efficiency and gross kinematics during treadmill roller skiing were compared between male world-class and national level sprint skiers (studies I-II), and between men and women matched for performance level (study III). Study I showed that maximal aerobic capacity, gross efficiency and high speed capacity differentiated world-class from national level sprint skiers. The study also indicated that low and moderate intensity endurance training and maximal speed training is important in attaining an international level in sprint skiing. Study II demonstrated that world-class sprint skiers had a higher gross efficiency than national level skiers. A general linear relationship between work rate and metabolic rate existed, indicating that gross efficiency at moderate and high work rates provides useful information about crosscountry skiers in standardized conditions during treadmill roller skiing. Furthermore, worldclass skiers used longer cycle lengths and lower cycle rates at a given speed and generated higher maximal speeds. In study III, men showed a 17% higher peak treadmill speed at a short and long incremental test compared to women. These gender differences were slightly greater than findings in comparable endurance sports. The majority of gender differences in performance could be explained by higher maximal oxygen uptakes and lower fat percentages in men. Men and women showed similar gross efficiency. However, women showed higher fractional utilization of maximal oxygen uptake at the anaerobic threshold. In studies IV-V, elite male skiers were analyzed for speeds, work rates, technique choices and gross kinematics during two sprint time-trial competitions on snow. Furthermore, the skiers were tested for physiological and kinematical characteristics in the laboratory. Study IV analyzed the time-trial of an international sprint competition. The results showed that performance on uphill and flat terrain strongly determined sprint time-trial performance, and that performance in the last half of the race differentiated most between skiers. Estimated work rates on an uphill section of the race were approximately 60% higher than the capacities which the skiers are able to cover aerobically. Peak oxygen uptake, gross efficiency, peak treadmill speed and peak cycle length were strongly related to sprint time-trial performance, particularly to the uphill and flat sections during the last part of the race. Study V analyzed a simulated sprint race by using a high end differential global navigation satellite system with simultaneous tracking of both GPS and GLONASS satellites. This provided an opportunity for more detailed analysis of cross-country skiing. Skiers encompassed a large speed range (2.9–12.9 m·s-1) and multiple transitions between skiing techniques (range: 21–34 transitions). The results demonstrated that performance in the uphill sections had the strongest correlation to sprint performance, and that the faster skiers used the G3 technique to a greater extent than the slower skiers. Thus, this provides new knowledge on physiological and biomechanical aspects of sprint skating performance, particularly that both the maximal aerobic and peak speed capacities differed between world-class and national level sprint skiers. Furthermore, gross efficiency, while treadmill roller skiing provides relevant information strongly related to sprint performance level. Better skiers also employ longer cycle lengths at the same absolute speeds and at individual peak speeds. The gender differences in performance were slightly larger than expected; however, most of these differences could be explained by a higher maximal oxygen uptake and a lower fat percentage in men. Furthermore, the variations in speeds, work rates and techniques and, especially, speed in uphill and flat terrain are important to the skiers’ total time-trial performance. Better sprint performance is related to more application of the G3 technique and to longer cycle lengths within this technique. Faster skiers showed higher peak oxygen uptake, gross efficiency and high speed capacity. These capacities were specifically correlated to the ability to maintain high speed on uphill and flat terrain throughout a sprint race.
Sprintlangrenn er ein fysiologisk og biomekanisk kompleks disiplin som blir utført som ein prolog og tre etterfølgjande utslagsløp. Konkurransetidene i kvart enkelt heat er 2-4 min og kan samanliknast med andre mellomdistanseidrettar. Sprintlangrenn blir imidlertid gjennomført i kupert terreng og med varierande arbeidsintensitet og innslag av ulike teknikkar som involverer underkropp og overkropp i ulik grad. Den overordna målsetjinga med denne avhandlinga var å undersøke fysiologiske og biomekaniske aspekt som er assosiert med prestasjonen i sprint skøyting hos elite langrennsløparar: 1) på rulleskitredemølle i laboratoriet (studia I-IV), 2) i sprintkonkurransar på snø (studia IV-V), og 3) for samanhengar mellom laboratorium-karakteristikkar og sprintprestasjonen på snø (studia IV-V). Studia I-III undersøker forskjellar i fysiologiske karakteristikkar, mekanisk effektivitet og kinematikk mellom mannlege verdsklasse og nasjonal klasse sprintlangrennsløparar (studia III) og mellom mannlege og kvinnelege sprintlangrennsløparar på tilsvarande prestasjonsnivå (studie III). Studie I viser at maksimal aerob kapasitet, mekanisk effektivitet og hurtigheit skil verdsklasse frå nasjonal klasse sprintlangrennsløparar. Studiet indikerer også at låg- og moderat-intensiv uthaldstrening og maksimal hurtigheitstrening er viktig for å nå internasjonalt nivå i sprintlangrenn. Studie II viser at verdsklasse sprintlangrennsløparar har betre mekanisk effektivitet enn løparar på nasjonalt nivå. Studiet viser ein generell lineær samanheng mellom arbeidsratar og energiforbruk og indikerer at målingar av mekanisk effektivitet gir nyttig og valid informasjon om langrennsløparar som blir samanlikna under standardiserte vilkår på rulleskitredemøller. Studiet demonstrerer også at verdsklasse løparane har lengre sykluslengder og lågare syklusfrekvens på ei gitt fart. Studie III viser at menn oppnår 17 % høgre fart enn kvinner både på ein kort og ein lang prestasjonstest med trinnvis aukande fart på rulleskitredemølla. Resultata indikerer at prestasjonsforskjellane mellom kjønna hovudsakleg kan forklarast av høgare maksimalt oksygenopptak og lågare feittprosent hos menn, og at forskjellane er noko større enn det litteraturen viser i andre tilsvarande uthaldsidrettar. Kvinner og menn har lik effektivitet, mens kvinner har høgare prosentvis utnytting av maksimalt oksygenopptak ved anaerob terskel. I studia IV-V vart fart, arbeidsratar, teknikkval og kinematikk undervegs i sprintkonkurransar undersøkt. Vidare blei samanhengar mellom fysiologiske og kinematiske karakteristikkar i laboratoriet og sprintprestasjonen på snø undersøkt. I studie IV vart prologen i ein internasjonal sprintkonkurranse analysert. Resultata viser at prestasjonen i motbakke og i flatt terreng er sterke forklaringsvariablar for den totale prologprestasjonen. Studiet indikerer også at prestasjonen i siste halvdelen av løypa skil løparane mest. Estimerte arbeidsratar i motbakke indikerer eit totalt arbeid omlag 60% høgare enn det løparane klarer å dekke med aerob energi. Maksimalt oksygenopptak, mekaniske effektivitet, fartskapasitet og sykluslengde var sterkt relatert til sprintprestasjonen, og spesielt til farta i flatt terreng og motbakkar i siste halvdelen av løpet. I studie V vart ein simulert sprintprolog analysert ved bruk av ein høgteknologisk differensial GPS, med svært høg samplingsfrekvens og nøyaktigheit, som hadde samtidig mottak av GPS- og GLONASS-satellittar. Løparane gjennomførte sprintkonkurransen i variert terreng, noko som førte til eit spenn i hastigheiter frå 2.9 til 12.9 m·s-1 og som inkluderte 21–34 teknikkendringar. Motbakkeprestasjonen var høgast korrelert til total prestasjon, og betre skiløparar brukte dobbeldansteknikken i større grad, samanlikna med mindre gode løparar. Samanfatta så bidreg denne avhandlinga med ny kunnskap om fysiologiske og biomekaniske aspekt av sprintlangrenn i skøyting. Det viser at både maksimal aerob kapasitet og fartskapasitet skil verdsklasse frå nasjonal klasse sprintlangrennsløparar. Det er også vist at målingar av mekanisk effektivitet på rulleskitredemølle gir valid informasjon og er sterkt relatert til prestasjonsnivået til løparane. Dei beste løparane bruker lengre sykluslengder både på same submaksimale fart og på si høgste individuelle fart. Forskjellane mellom mannlege og kvinnelege sprintløparar i prestasjon er noko større enn forventa. Det meste av desse kjønnsforskjellane kan forklarast av at menn har høgare maksimalt oksygenopptak og lågare feittprosent. Undervegs i sprintprologar viser løparane store variasjonar i fart, arbeidsratar og vekslar stadig mellom ulike teknikkar. Spesielt er farta i motbakkar og flatt terreng mot slutten av løpa betydningsfull for prologprestasjonen. Betre prologprestasjon er linka til meir bruk av dobbeldansteknikken og lengre sykluslengder innan denne teknikken. Betre utøvarar har også høgare maksimalt oksygenopptak, effektivitet og fartskapasiet, noko som vart relatert til evna til å oppretthalde høg fart i motbakkar og flatt terreng gjennom eit sprintløp.

This study uses adaptation of an established 3-D biomechanical shoulder model (Newcastle Shoulder Model) to investigate the biomechanical properties of reverse shoulder replacements that have become popular for severe rotator cuff arthropathy. The prosthetic model describes the DELTA® III geometry and can predict muscle and joint contact forces for given motion. A custom contact detection algorithm was developed to investigate the impingement problem. Results showed that the reverse design increases deltoid function by providing sufficient moment arm (42% increase compared to normal anatomy) and restores joint stability by reversing the envelope of joint contact forces. The data showed a good agreement with other biomechanical models. Further in this study scapula and arm kinematics of a group of DELTA III prosthetic subjects were recorded and compared with normal shoulder activity. The scapula kinematics showed increased lateral rotation and even if it is highly variable within the subjects (range:1.2-1.8 times the normal). there is a trend showing that good recovery shoulders have small change in their scapula rhythm and vice versa. The arm kinematics showed that even if the prosthetic subjects were able to complete most activities there was a variable range of humeral movement. Compared to the normal group the average elevation values were high but the internal/external humeral rotation was significantly smaller. The kinematic data were further used and analysed with the model and the results showed large differences in glenoid loading compared to normal shoulders. where there is an increase in superior (range:12%-52% bodyweight) and antero-posterior shear forces (range:8%-39% bodyweight). Impingement results predicted scapula bone notches similar in shape and volume with the literature which was impossible to eliminate without design modifications. The adapted prosthetic model was successfully used to analyse the biomechanics of a reverse design and provide a useful dataset that can be further used for design optimisation.

This thesis focuses on the problem of determining appropriate skeletal configurations for which a virtual animated character moves to desired positions as smoothly, rapidly, and as accurately as possible. During the last decades, several methods and techniques, sophisticated or heuristic, have been presented to produce smooth and natural solutions to the Inverse Kinematics (IK) problem. However, many of the currently available methods suffer from high computational cost and production of unrealistic poses. In this study, a novel heuristic method, called Forward And Backward Reaching Inverse Kinematics (FABRIK), is proposed, which returnsvisually natural poses in real-time, equally comparable with highly sophisticated approaches. It is capable of supporting constraints for most of the known joint types and it can be extended to solve problems with multiple end effectors, multiple targets and closed loops. FABRIK wascompared against the most popular IK approaches and evaluated in terms of its robustness and performance limitations. This thesis also includes a robust methodology for marker prediction under multiple marker occlusion for extended time periods, in order to drive real-time centre of rotation (CoR) estimations. Inferred information from neighbouring markers has been utilised, assuming that the inter-marker distances remain constant over time. This is the firsttime where the useful information about the missing markers positions which are partially visible to a single camera is deployed. Experiments demonstrate that the proposed methodology can effectively track the occluded markers with high accuracy, even if the occlusion persists for extended periods of time, recovering in real-time good estimates of the true joint positions. In addition, the predicted positions of the joints were further improved by employing FABRIK to relocate their positions and ensure a fixed bone length over time. Our methodology is tested against some of the most popular methods for marker prediction and the results confirm that our approach outperforms these methods in estimating both marker and CoR positions. Finally, an efficient model for real-time hand tracking and reconstruction that requires a minimumnumber of available markers, one on each finger, is presented. The proposed hand modelis highly constrained with joint rotational and orientational constraints, restricting the fingers and palm movements to an appropriate feasible set. FABRIK is then incorporated to estimate the remaining joint positions and to fit them to the hand model. Physiological constraints, such as inertia, abduction, flexion etc, are also incorporated to correct the final hand posture. A mesh deformation algorithm is then applied to visualise the movements of the underlying hand skeleton for comparison with the true hand poses. The mathematical framework used for describing and implementing the techniques discussed within this thesis is Conformal GeometricAlgebra (CGA).

The purpose of this project was to quantify and analyze the changes that occur to the moments of force and moment powers at the joints of the lower extremity during stair and ramp descent. Methods. A sample population of five male and five female volunteers were asked to walk five times down a 10-degree ramp at normal gait speed, followed by five stair descent trials. Results and discussion. Stair descent has a larger eccentric plantar flexor peak at the ankle joint during weight acceptance. The knee exhibits slightly larger eccentric knee extensor peaks during ramp descent at push - off and there was higher loading of the hip during ramp descent as compared with stair descent. The higher ankle powers at FS during stair descent reveal a concern for those people suffering from ankle pathology and the larger hip and knee peaks during ramp descent is of concern to those with hip and knee problems. These results could be used in the rehabilitative considerations of patients with hip, knee and ankle replacements and as a baseline for future research. (Abstract shortened by UMI.)

Hip simulators are designed to reproduce the forces and motion patterns of normal walking. In vivo demands on total hip replacements, however, are varied and often more severe than normal walking conditions. It is these severe conditions that often lead to implant failure. This is clinically based research aimed at understanding some of the more severe conditions in hips and the effect that these have on the performance of the total hip replacement. The polyethylene liner can act as a pump in an acetabular component, forcing fluid and wear particles through the holes to the retroacetabular bone causing osteolysis. Ten patients were studied at revision surgery. Pressures were measured in retroacetabular osteolytic lesions while performing pumping manouvers with the hip. Two laboratory experiments were then designed to study pumping mechanisms in vitro. In patients with contained osteolytic lesions, fluid pressure fluctuations could be measured in the lesion in association with the pumping action. Patients with uncontained osteolytic lesions showed no such pressure fluctuations. In the laboratory we identified 3 distinct mechanisms whereby fluid can be pumped from the hip joint to the retroacetabular bone. These pumping effects could be mitigated by improved implant design. Loading of the femoral head against the edge of the acetabular component produces dramatically increased contact pressures particularly in hard-on-hard bearings. In an analysis of 16 retrieved ceramic-on-ceramic bearings we were able to characterise the mechanism of edge loading based on the pattern of edge loading wear on the bearing surface. Finally in a radiographic study of patients with squeaking ceramic-on-ceramic hips. Squeaking was found to be associated with acetabular component malposition. It seems that edge loading or impingement may be an associated factor in these cases.

A significant number of non-institutionalized older adults have difficulty rising from a chair. Although there exist several assistive devices to aid with sit to stand, there is a lack of research that compares and analyzes various modes of assisted sit to stand to characterize their relative effectiveness in terms of biomechanical metrics. In addition, few existing assistive devices have been designed specifically to share between the user and the device the force required to rise, an approach that has the benefit of maintaining both the mobility and muscular strength of the user. This thesis advances our understanding of different modes of load-sharing sit to stand through empirical quantification. A specially-designed sit-to-stand test bed with load sharing capabilities was fabricated for human-subjects experiments. In addition to an unassisted rise and a static assist using a grab bar, three mechatronic modes of assist, at the seat, waist and arms, were implemented. The test bed employs a closed-loop load-sharing control scheme to require a user to provide a portion of the effort needed for a successful rise motion. Experiments were performed with 17 healthy older adults using the five aforementioned modes of rise. Force and kinematic sensor measurements obtained during the rise were used as inputs into a biomechanical model of each subject, and each mode of rise was evaluated based on key biomechanical metrics extracted from this model relating to stability, knee effort reduction, and rise trajectory. In addition, a questionnaire was administered to determine subjective response to and preference for each rise type. Results show that the seat and waist assists provide statistically significant improvements in terms of stability and knee effort reduction, while the arm and bar assists do not provide any biomechanical improvement from the unassisted rise. The assists most preferred by the subject were the seat and bar assists. Because of subject preference and biomechanical improvements, of the modes tested, the seat assist was determined to be the best mode of providing assistance with sit to stand.

The field of research of this dissertation concerns the bioengineering of exercise, in particular the relationship between biomechanical and metabolic knowledge. This relationship can allow to evaluate exercise in many different circumstances: optimizing athlete performance, understanding and helping compensation in prosthetic patients and prescribing exercise with high caloric consumption and minimal joint loading to obese subjects. Furthermore, it can have technical application in fitness and rehabilitation machine design, predicting energy consumption and joint loads for the subjects who will use the machine. The aim of this dissertation was to further understand how mechanical work and metabolic energy cost are related during movement using interpretative models. Musculoskeletal models, when including muscle energy expenditure description, can be useful to address this issue, allowing to evaluate human movement in terms of both mechanical and metabolic energy expenditure. A whole body muscle-skeletal model that could describe both biomechanical and metabolic aspects during movement was identified in literature and then was applied and validated using an EMG-driven approach. The advantage of using EMG driven approach was to avoid the use of arbitrary defined optimization functions to solve the indeterminate problem of muscle activations. A sensitivity analysis was conducted in order to know how much changes in model parameters could affect model outputs: the results showed that changing parameters in between physiological ranges did not influence model outputs largely. In order to evaluate its predicting capacity, the musculoskeletal model was applied to experimental data: first the model was applied in a simple exercise (unilateral leg press exercise) and then in a more complete exercise (elliptical exercise). In these studies, energy consumption predicted by the model resulted to be close to energy consumption estimated by indirect calorimetry for different intensity levels at low frequencies of movement. The use of muscle skeletal models for predicting energy consumption resulted to be promising and the use of EMG driven approach permitted to avoid the introduction of optimization functions. Even though many aspects of this approach have still to be investigated and these results are preliminary, the conclusions of this dissertation suggest that musculoskeletal modelling can be a useful tool for addressing issues about efficiency of movement in healthy and pathologic subjects.
L’ambito di ricerca di questa tesi riguarda la bioingegneria dell’esercizio fisico, in particolare l’integrazione tra conoscenze biomeccaniche e metaboliche. La relazione tra questi due aspetti consentirebbe una valutazione completa dell’esercizio fisico che potrebbe aiutare la pratica clinica in diversi ambiti (ottimizzazione della performance di atleti, comprensione e compensazione del consumo energetico nei pazienti protesizzati, identificazione di esercizi ad alto consumo calorico e basso carico alle articolazioni per pazienti in sovrappeso). Inoltre, potrebbe avere applicazioni tecniche nel design di macchine per il fitness e per la riabilitazione. Lo scopo di questo lavoro era di approfondire la conoscenza riguardante la relazione tra lavoro meccanico e costo energetico metabolico durante il movimento, attraverso l’utilizzo di modelli interpretativi. Il problema è stato affrontato attraverso l’utilizzo di modelli muscolo scheletrici che includono oltre alla descrizione meccanica anche la descrizione della spesa energetica muscolare e che quindi permettono di valutare il movimento umano sia in termini meccanici che in termini di spesa energetica. E’ stato identificato in letteratura un modello muscolo scheletrico dell’intero corpo che potesse descrivere sia aspetti meccanici che metabolici; tale modello è stato applicato e validato utilizzando un approccio guidato da dati sperimentali di cinematica e elettromiografia (EMG-driven). Il vantaggio principale nell’utilizzo di un approccio EMG-driven è evitare l’introduzione di funzioni di ottimizzazione arbitrarie che servono per risolvere il problema indeterminato delle forze muscolari attorno alle articolazioni. E’ stata quindi condotta un’analisi di sensitività sul modello con lo scopo di conoscere quanto le variazioni nei parametri possono influire sulle uscite del modello stesso: i risultati hanno mostrato che variazioni dei parametri all’interno di range fisiologici non influenzano largamente le uscite del modello. Successivamente, il modello muscolo scheletrico è stato applicato ai dati sperimentali al fine di valutare la sua capacità predittiva: la valutazione è stata prima effettuata su un esercizio semplice (leg press unilaterale) e poi su uno più completo (esercizio ellittico). Le predizioni energetiche del modello sono risultate vicine ai dati di consumo energetici stimati tramite calorimetria indiretta nei casi studiati, in particolare alle basse velocità di esercizio e a diversi livelli di intensità. In conclusione, l’utilizzo di modelli muscolo scheletrici per predire il consumo energetico è risultato promettente e l’uso di un approccio EMG-driven ha permesso di evitare l’utilizzo di funzioni di ottimizzazione. Sebbene i risultati ottenuti siano preliminari e molti aspetti dell’approccio proposto debbano essere ulteriormente studiati, le conclusioni di questa tesi suggeriscono che la modellazione muscolo scheletrica può essere uno strumento utile per rispondere a domande riguardanti l’efficienza del movimento in soggetti sani o patologici.