Quantification of knee extensor muscle forces: a multimodality approach

Given the growing interest of using musculoskeletal (MSK) models in a large number of clinical applications for quantifying the internal loading of the human MSK system, verification and validation of the model’s predictions, especially at the knee joint, have remained as one of the biggest challenges in the use of the models as clinical tools. This thesis proposes a methodology for more accurate quantification of knee extensor forces by exploring different experimental and modelling techniques that can be used to enhance the process of verification and validation of the knee joint model within the MSK models for transforming the models to a viable clinical tool. In this methodology, an experimental protocol was developed for simultaneous measurement of the knee joint motion, torques, external forces and muscular activation during an isolated knee extension exercise. This experimental protocol was tested on a cohort of 11 male subjects and the measurements were used to quantify knee extensor forces using two different MSK models representing a simplified model of the knee extensor mechanism and a previously-developed three-dimensional MSK model of the lower limb. The quantified knee extensor forces from the MSK models were then compared to evaluate the performance of the models for quantifying knee extensor forces. The MSK models were also used to investigate the sensitivity of the calculated knee extensor forces to key modelling parameters of the knee including the method of quantifying the knee centre of rotation and the effect of joint translation during motion. In addition, the feasibility of an emerging ultrasound-based imaging technique (shear wave elastography) for direct quantification of the physiologically-relevant musculotendon forces was investigated. The results in this thesis showed that a simplified model of the knee can be reliably used during a controlled planar activity as a computationally-fast and effective tool for hierarchical verification of the knee joint model in optimisation-based large-scale MSK models to provide more confidence in the outputs of the models. Furthermore, the calculation of knee extensor muscle forces has been found to be sensitive to knee joint translation (moving centre of rotation of the knee), highlighting the importance of this modelling parameter for quantifying physiologically-realistic knee muscle forces in the MSK models. It was also demonstrated how the movement of the knee axis of rotation during motion can be used as an intuitive tool for understanding the functional anatomy of the knee joint. Moreover, the findings in this thesis indicated that the shear wave elastography technique can be potentially used as a novel method for direct quantification of the physiologically-relevant musculotendon forces for independent validation of the predictions of musculotendon forces from the MSK models.Open Acces

Stretch hyperreflexia in children with cerebral palsy:Assessment - Contextualization - Modulation

Cerebral palsy (CP) is a neurological disorder and the most frequent cause of motor impairment in children in Europe. Around 85% of children with CP experience stretch hyperreflexia, also known as “spasticity”. Stretch hyperreflexia is an excessive response to muscle stretch, leading to increased joint resistance. The joint hyper-resistance causes limitations in activities such as walking. Multiple methods have been developed to measure stretch hyperreflexia, but evidence supporting the use of these methods for diagnostics and treatment evaluation in children with CP is insufficient. Furthermore, most methods are designed to assess stretch reflexes in passive conditions, which might not translate to the limitations encountered due to stretch reflexes during activities. Furthermore, while a broad range of stretch hyperreflexia treatments is available, many are invasive, non-specific, or temporary and might have adverse side effects. Training methods to reduce stretch reflexes using biofeedback are promising non-invasive methods with potential long-term sustained effects. Still, clinical feasibility needs to be improved before implementation in clinical rehabilitation of children with CP. This thesis aimed to develop methods to assess stretch hyperreflexia of the calf muscles during passive conditions, as well as in the context of walking. Additionally, this thesis aimed to develop clinically feasible methods to modulate stretch hyperreflexia in the calf muscle of children with CP. The outcomes are described in eight different studies presented in this thesis. All in all, the work presented in this thesis shows that sagittal plane clinical gait analysis can be performed using the human body model and can be complemented with ultrasound imaging of the calf muscle. Motorized methods to assess stretch hyperreflexia in passive conditions might be useful for evaluation in adults after SCI/Stroke. Still, limitations regarding feasibility and validity limit clinical application for children with CP. Furthermore, this thesis provides additional evidence that the deviating muscle activation patterns during walking, particularly the increased activation around initial contact, are caused by stretch hyper-reflexes in children with CP. The deviating muscle activation patterns, with increased activation during early stance and reduced activation around push-off, can be modulated within one session by several children with CP. Therefore, the next step is to develop a training program to modulate the activation pattern and potentially decrease stretch hyper-reflexes in children with CP to improve the gait patter

Modelling and in vivo evaluation of tendon forces and strain in dynamic rehabilitation exercises: a scoping review

Objectives Although exercise is considered the preferred approach for tendinopathies, the actual load that acts on the tendon in loading programmes is usually unknown. The objective of this study was to review the techniques that have been applied in vivo to estimate the forces and strain that act on the human tendon in dynamic exercises used during rehabilitation. Design Scoping review. Data sources Embase, PubMed, Web of Science and Google Scholar were searched from database inception to February 2021. Eligibility criteria Cross-sectional studies available in English or Spanish language were included if they focused on evaluating the forces or strain of human tendons in vivo during dynamic exercises. Studies were excluded if they did not evaluate tendon forces or strain; if they evaluated running, walking, jumping, landing or no dynamic exercise at all; and if they were conference proceedings or book chapters. Data extraction and synthesis Data extracted included year of publication, study setting, study population characteristics, technique used and exercises evaluated. The studies were grouped by the types of techniques and the tendon location. Results Twenty-one studies were included. Fourteen studies used an indirect methodology based on inverse dynamics, nine of them in the Achilles and five in the patellar tendon. Six studies implemented force transducers for measuring tendon forces in open carpal tunnel release surgery patients. One study applied an optic fibre technique to detect forces in the patellar tendon. Four studies measured strain using ultrasound-based techniques. Conclusions There is a predominant use of inverse dynamics, but force transducers, optic fibre and estimations from strain data are also used. Although these tools may be used to make general estimates of tendon forces and strains, the invasiveness of some methods and the loss of immediacy of others make it difficult to provide immediate feedback to the individuals.This work is part of a government-funded project supported by the University Teaching Training Programme (FPU) of the Ministry of Science, Innovation and Universities of Spain. Grant number: FPU17/00161. The University of Malaga has supported this study with the contribution of funds to support its publication in open access

What are the differences between subjects with and without flatfoot condition, with the aid of ultrasonography, kinematics, and kinetics in posture and gait?

O complexo do pé tem um papel importante na postura, equilíbrio, estabilidade e movimento, durante as posições estáticas e nos padrões gerais de movimento. Alterações estruturais ou funcionais no complexo do pé e no seu posicionamento podem afetar a postura e o movimento das estruturas distais e proximais. Comumente, indivíduos com pé plano desenvolvem restrições neurológicas ou musculares, frouxidão ligamentar ou articular, movimento excessivo e atividade muscular. Essa condição leva a maiores riscos de desenvolver lesões por sobrecarga mecânica nas articulações dos membros inferiores adjacentes. O objetivo é determinar se existem diferenças entre indivíduos com pé plano em comparação com indivíduos com pé neutro, em relação à postura e à análise do padrão de marcha. A amostra foi constituída por sujeitos com pé plano e neutro, alocados em dois grupos. Todos os sujeitos foram submetidos a procedimentos de avaliação para serem alocados em um dos grupos. Cada participante foi submetido à avaliação do padrão de marcha e postura, com auxílio de sistema MOCAP, e à avaliação da rigidez muscular com Ultrassonografia e, por fim, à avaliação da pressão plantar com uma plataforma de pressões. Os sujeitos com pé plano mostraram várias alterações e diferenças quando comparados aos participantes com pé neutro, de acordo com os principais resultados da análise da postura e do padrão de marcha. Considerando todos os estudos realizados e incluídos nesta tese, várias diferenças foram encontradas em indivíduos de pé plano. Porém, a maioria desses resultados são contraditórios com os resultados presentes na literatura, dando um crescimento da evidência científica sobre a condição de pé plano e a sua influência na postura, e no padrão de marcha. No entanto, em relação à falta de consenso sobre os resultados e condições de avaliação, vários estudos necessitam ser realizados para criar uma maior robustez da evidência científica. Porém, no que se refere ao rigor metodológico em relação a diferentes parâmetros, novos estudos precisam de abranger variáveis que foquem a avaliação geral da condição e não apenas do complexo do pé. Palavras-chave: POSTURA DE PÉ, PADRÕES DE MOVIMENTO, PÈ PLANO, BIOMECÂNICA.The foot complex has an important role in posture, balance, stability, and movement, during the static positions and in overall movements' patterns. Structural or functional alteration in the foot complex and foot posture may have an impact on posture and movement on distal and proximal structures. Commonly, subjects with flatfoot develop neurological or muscular restrictions, ligament or joint laxity, excessive motion, and muscle activity. This condition leads to higher risks of developing mechanical overloading injuries on adjacent lower-limb joints. The aim of this study is to determine if there are differences between flatfoot subjects compared to neutral foot subjects, regarding posture and gait pattern analysis. The sample was constituted by subjects with a flat and neutral foot, allocated in two groups. All subjects were submitted to assessment procedures to be allocated in one of the groups. Therefore, each participant was submitted to gait pattern and posture assessment, with the aid of a MOCAP system, and to muscle stiffness assessment with an ultrasound-based Shear- Wave Elastography and, finally to plantar pressure assessment with a baropodometric platform. Flatfoot subjects showed several alterations and differences when compared to neutral foot participants considering all principal outcomes along with posture and gait pattern. Considering all studies realized and included in this thesis, several differences were found in flatfoot subjects. Thus, most of those results are contradictory to those found in the literature, giving a growth of evidence relatively to foot posture condition and influence in posture and gait pattern. However, regarding the lack of consensus about the outcomes and assessment conditions, further studies need to be performed to create a more robust body of evidence. Although, regarding methodological deficiency regarding influencing aspects, further studies need to encompass methodological variables handling to focus on an overall evaluation of the condition and not only on the foot complex

Current understanding of the diagnosis and management of the tendinopathy: An update from the lab to the clinical practice

[Abstract] Tendinopathy is labeled by many authors as a troublesome, common pathology, present in up to 30% medical care con- sultations involving musculoskeletal conditions. Despite the lasting interest for addressing tendon pathology, current re- searchers agree that even the exact definition of the term tendinopathy is unclear. Tendinopathy is currently diagnosed as a clinical hypothesis based on the patient symptoms and physical context. One of the main goals of current clinical management is to personalize treatment approaches to adapt them to the many different needs of the population. Tendons are complex structures that unite muscles and bones with two main objectives: to transmit forces and stor- age and release energy. Regarding the tensile properties of the tendons, several authors argued that tendons have higher tensile strength compared with muscles, however, are con- sidered less flexible. Tendinopathy is an accepted term which is used to indicated a variety of tissue conditions that appear in injured tendons and describes a non-rupture damage in the tendon or para- tendon, which is intensified with mechanical loading Even when the pathoetiology of tendinopathy is unclear, there is a wide array of treatments available to treat and manage tendinopathy. Although tendinitis usually debuts with an in- flammatory response, the majority of chronic tendinopathies do not present inflammation and so the choosing of treat- ment should vary depending on severity, compliance, pain and duration of symptoms. The purpose of this article is to review and provide an overview about the currently research of the tendon diagno- sis, management and etiology

Consideration of monoarticular and biarticular mechanisms

Aktuelle In-vivo-Methoden zur Bewertung der Belastung und Dehnung der Achillessehne (AT) in der biomechanischen Literatur haben bestimmte Einschränkungen, die sorgfältig berücksichtigt werden müssen. Daher hatte die erste Studie zum Ziel, die AT-Dehnung und -Kraft während der Fortbewegung mithilfe einer genauen, nicht-invasiven Methode zu messen. Die Länge der AT wurde unter Berücksichtigung ihrer Krümmung mit reflektierenden Folienmarkern von der Insertion am Fersenbein bis zum Übergang zwischen der Muskel-Sehnen-Verbindung des Musculus gastrocnemius medialis (GM-MTJ) gemessen. Die Kraft der AT wurde durch Anpassung einer quadratischen Funktion an die experimentelle Kraft-Längen-Kurve der Sehne ermittelt, die aus maximalen freiwilligen isometrischen Kontraktionen (MVC) gewonnen wurde. Die Ergebnisse der zweiten Studie zeigen, dass eine Erhöhung der Gehgeschwindigkeit zu einer 21%igen Abnahme der maximalen AT-Kraft bei höheren Geschwindigkeiten im Vergleich zur bevorzugten Geschwindigkeit führt, während die Nettobelastung der AT-Kraft am Sprunggelenk (ATF-Arbeit) in Abhängigkeit von der Gehgeschwindigkeit zunimmt. Darüber hinaus trugen eine frühere Plantarflexion, erhöhte elektromyografische Aktivität der Muskeln Sol und GM sowie der Energieübertrag von Knie- zu Sprunggelenk durch die biartikulären Musculi gastrocnemii zu einer 1,7- bzw. 2,4-fachen Zunahme der netto ATF-Mechanik-Arbeit bei Übergangs- und maximalen Gehgeschwindigkeiten bei. Das Ziel der dritten Studie war es, die in der ersten Studie vorgeschlagene Methode zu vereinfachen, indem die Anzahl der reflektierenden Folienmarker reduziert wurde, jedoch die hohe Genauigkeit beibehalten wurde. Die Krümmung der AT wurde mithilfe von reflektierenden Folienmarkern zwischen dem Ursprung des GM-MTJ und dem Einführungsmarker am Fersenbein beurteilt. Unsere Ergebnisse zeigen, dass eine Reduzierung der Anzahl der Folienmarker um 70% beim Gehen und um 50% beim Laufen zu einem marginalen Fehler führen würde und somit einen vernachlässigbaren Effekt auf die Länge der AT und die maximale Dehnungsmessung hätte.Current in vivo methods to assess the Achilles tendon (AT) strain and loading in the biomechanics literature have certain limitations that require careful consideration. Therefore, the first study was to measure the AT strain and quantify AT force during locomotion with an accurate non-invasive method. AT length was measured considering its curvature using reflective foil markers from AT insertion at calcaneus to gastrocnemius medialis muscle-tendon junction (GM-MTJ). The force of the AT was calculated by fitting a quadratic function to the experimental tendon force-length curve obtained from maximum voluntary isometric contractions (MVC). The findings in second study indicate that an increase in walking speed leads to a 21% decrease in maximum AT force at higher speeds compared to the preferred speed, yet the net work of the AT force at the ankle joint (ATF-work) increased as a function of walking speed. Additionally, an earlier plantar flexion, increased electromyographic activity of the Sol and GM muscles, and knee-to-ankle joint energy transfer via the biarticular gastrocnemii contributed to a 1.7 and 2.4-fold increase in the net ATF-mechanical work in the transition and maximum walking speeds. The objective of the third study was to simplify the proposed method in the first study by reducing the number of foil reflective markers while preserving high accuracy. The AT curvature was assessed using reflective foil markers between the GM-MTJ origin and the calcaneal insertion marker. Our results indicate that reducing the number of foil markers by 70% during walking and 50% during running would result in a marginal error and, thus, a negligible effect on the AT length and maximum strain measurement

The Relationship Between Medial Gastrocnemius Lengthening Properties and Stretch Reflexes in Cerebral Palsy

Stretch reflex hyperactivity in the gastrocnemius of children with spastic cerebral palsy (CP) is commonly evaluated by passively rotating the ankle joint into dorsiflexion at different velocities, such as applied in conventional clinical spasticity assessments. However, surface electromyography (sEMG) collected from the medial gastrocnemius (MG) during such examination reveals unexplained heterogeneity in muscle activation between patients. Recent literature also highlights altered muscle tensile behavior in children with spastic CP. We aimed to document MG muscle and tendon lengthening during passive ankle motion at slow and fast velocity and explore its interdependence with the elicited hyperactive stretch reflex. The ankle of 15 children with CP (11 ± 3 years, GMFCS 9I 6II, 8 bilateral, 7 unilateral) and 16 typically developing children (TDC) was passively rotated over its full range of motion at slow and fast velocity. Ultrasound, synchronized with motion-analysis, was used to track the movement of the MG muscle-tendon junction and extract the relative lengthening of muscle and tendon during joint rotation. Simultaneously, MG sEMG was measured. Outcome parameters included the angular and muscle lengthening velocities 30 ms before EMG onset and the gain in root mean square EMG during stretch, as a measure of stretch reflex activity. Compared to slow rotation, the muscle lengthened less and stretch reflex activity was higher during fast rotation. These velocity-induced changes were more marked in CP compared to TDC. In the CP group, muscle-lengthening velocity had higher correlation coefficients with stretch reflex hyperactivity than joint angular velocity. Muscles with greater relative muscle lengthening during slow rotation had earlier and stronger stretch reflexes during fast rotation. These initial results suggest that ankle angular velocity is not representative of MG muscle lengthening velocity and is less related to stretch reflex hyperactivity than MG muscle lengthening. In addition, muscles that lengthened more during slow joint rotation were more likely to show a velocity-dependent stretch reflex. This interdependence of muscle lengthening and stretch reflexes may be important to consider when administering treatment. However, muscle and tendon lengthening properties alone could not fully explain the variability in stretch reflexes, indicating that other factors should also be investigated

Ultrasonography for the prediction of musculoskeletal function

Ultrasound (US) imaging is a well-recognised technique for studying in vivo characteristics of a range of biological tissues due to its portability, low cost and ease of use; with recent technological advances that increased the range of choices regarding acquisition and analysis of ultrasound data available for studying dynamic behaviour of different tissues. This thesis focuses on the development and validation of methods to exploit the capabilities of ultrasound technology to investigate dynamic properties of skeletal muscles in vivo exclusively using ultrasound data. The overarching aim was to evaluate the influence of US data properties and the potential of inference algorithms for prediction of net ankle joint torques. A fully synchronised experimental setup was designed and implemented enabling collection of US, Electromyography (EMG) and dynamometer data from the Gastrocnemius medialis muscle and ankle joint of healthy adult volunteers. Participants performed three increasing complexity muscle movement tasks: passive joint rotations, isometric and isotonic contractions. Two frame rates (32 and 1000 fps) and two data precisions (8 and 16-bits) were obtained enabling analysis of the impact of US data temporal resolution and precision on joint torque predictions. Predictions of net joint torque were calculated using five data inference algorithms ranging from simple regression through to Artificial Neural Networks. Results indicated that accurate predictions of net joint torque can be obtained from the analysis of ultrasound data of one muscle. Significantly improved predictions were observed using the faster frame rate during active tasks, with 16-bit data precision and ANN further improving results in isotonic movements. The speed of muscle activation and complexity of fluctuations of the resulting net joint torques were key factors underpinning the prediction errors recorded. The properties of collected US data in combination with the movement tasks to be assessed should therefore be a key consideration in the development of experimental protocols for in vivo assessment of skeletal muscles