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

Imaging and simulation of Achilles tendon dynamics: Implications for walking performance in the elderly

The Achilles tendon (AT) is a complex structure, consisting of distinct fascicle bundles arising from each triceps surae muscle that may act as mechanically independent structures. Advances in tissue imaging are rapidly accelerating our understanding of the complexities of functional Achilles tendon behavior, with potentially important implications for musculoskeletal injury and performance. In this overview of our recent contributions to these efforts, we present the results of complementary experimental and computational approaches to investigate AT behavior during walking and its potential relevance to reduced triceps surae mechanical performance due to aging. Our experimental evidence reveals that older tendons exhibit smaller differences in tissue deformations than young adults between regions of the AT presumed to arise from the gastrocnemius and soleus muscles. These observations are consistent with a reduced capacity for inter-fascicle sliding within the AT, which could have implications for the mechanical independence of the triceps surae muscles. More uniform AT deformations are also correlated with hallmark biomechanical features of elderly gait – namely, a loss of net ankle moment, power, and positive work during push-off. Simulating age-related reductions in the capacity for inter-fascicle sliding in the AT during walking predicts detriments in gastrocnemius muscle-tendon mechanical performance coupled with underlying shifts in fascicle kinematics during push-off. AT compliance, also suspected to vary due to age, systematically modulates those effects. By integrating in vivo imaging with computational modeling, we have gained theoretical insight into multi-scale biomechanical changes due to aging, hypotheses regarding their functional effects, and opportunities for experiments that validate or invalidate these assertions

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

Altered Tendon Characteristics and Mechanical Properties Associated with Insertional Achilles Tendinopathy

Study Design: Case-control laboratory study. Objectives: To compare tendon characteristics (shape, composition) and mechanical properties (strain, stiffness) on the involved side of participants with insertional Achilles tendinopathy (IAT) to the uninvolved side and to controls, and to examine if severity of tendon pathology is associated with severity of symptoms during function. Background: Despite the severity and chronicity of IAT, the quality of theoretical evidence available to guide the development of exercise interventions is low. While tendon pathology of midportion Achilles tendinopathy has been described, there are few studies specific to IAT. Methods: Twenty individuals with unilateral IAT and 20 age- and sex-matched controls volunteered to participate. Ultrasound imaging was used to quantify changes in tendon shape (diameter) and composition (echogenicity). A combination of ultrasound and dynamometry was used to measure tendon mechanical properties (strain and stiffness) during passive ankle rotation toward dorsiflexion. Generalized estimating equations were used to examine the association between IAT, alterations in tendon properties, and participant demographics. Pearson correlation was used to examine the association between severity of tendon pathology and severity of symptoms (Victorian Institute of Sport Assessment-Achilles). Results: The side with IAT had a larger tendon diameter (P Conclusion: Ultrasound imaging combined with dynamometry can discriminate alterations in tendon shape, composition, and mechanics in participants with IAT. Future clinical trials for IAT may consider strategies to alter tendon characteristics and restore tendon mechanic

Methodological and anatomical modifiers of Achilles tendon moment arm estimates implications for biomechanical modelling: Implications for biomechanical modelling

This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.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

Tendinous tissue adaptation to explosive-vs. sustained-contraction strength training

The effect of different strength training regimes, and in particular training utilizing brief explosive contractions, on tendinous tissue properties is poorly understood. This study compared the efficacy of 12 weeks of knee extensor explosive-contraction (ECT; n = 14) vs. sustained-contraction (SCT; n = 15) strength training vs. a non-training control (n = 13) to induce changes in patellar tendon and knee extensor tendon-aponeurosis stiffness and size (patellar tendon, vastus-lateralis aponeurosis, quadriceps femoris muscle) in healthy young men. Training involved 40 isometric knee extension contractions (3 times/week): gradually increasing to 75% of maximum voluntary torque (MVT) before holding for 3 s (SCT), or briefly contracting as fast as possible to ~80% maximum voluntary torque (ECT). Changes in patellar tendon stiffness and Young’s modulus, tendon-aponeurosis complex stiffness, as well as quadriceps femoris muscle volume, vastus-lateralis aponeurosis area and patellar tendon cross-sectional area were quantified with ultrasonography, dynamometry, and magnetic resonance imaging. ECT and SCT similarly increased patellar tendon stiffness (20% vs. 16%, both p < 0.05 vs. control) and Young’s modulus (22% vs. 16%, both p < 0.05 vs. control). Tendon-aponeurosis complex high-force stiffness increased only after SCT (21%; p <0.02), while ECT resulted in greater overall elongation of the tendon-aponeurosis complex. Quadriceps muscle volume only increased after sustained-contraction training (8%; p = 0.001), with unclear effects of strength training on aponeurosis area. The changes in patellar tendon cross-sectional area after strength training were not appreciably different to control. Our results suggest brief high force muscle contractions can induce increased free tendon stiffness, though SCT is needed to increase tendon-aponeurosis complex stiffness and muscle hypertrophy

Evaluation of ultrasound data from the MARES Sinusoidal Perturbation Protocol for the analysis of vibration-induced changes in fascicle length and pennation angle as a function of vibration frequency and muscular preload

Background: Vibration exposure has proven to be a useful training method and examination method in a variety of contexts. Nevertheless, not much is known about the mechanical properties of muscle tendon unit during vibration exposure. Therefore, the main aim of this study was to get an insight into vibration-induced changes in fascicle length and pennation angle at different frequencies and levels of contraction. Methods: 23 subjects performed the sinusoidal perturbation protocol before and after 60 days of bed rest. Ultrasound videos of gastrocnemius medialis were recorded during vibration exposure at 10 different frequencies (4 – 16 Hz) and 4 levels of contraction (0, 25, 50 and 75% MVC). Excursion of fascicle length (FL) and pennation angle (PEN) was evaluated using an ultrasound tracking software. Results: Excursion of FL and PEN was significantly smaller when muscle was contracted. For the range from 7 to 10 Hz there was a significant increase in excursion for pre-tensioned muscle, especially for FL. After bed rest, excursion was significantly greater at 9 Hz and 10 Hz vibration for FL and at 8, 9 and 10 Hz for PEN, respectively. Conclusion: Fascicle excursion decreases as the muscle contracts. However, no further correlation between the level of contraction and the decrease in excursion could be found. The main finding of this study was a significant resonance effect at 7-10 Hz vibration and contracted muscle. Resonance was even more evident after bed rest

Ultrasound assessment of deep fascia sliding mobility in vivo: a scoping review

Introdução: A falha do deslizamento fascial pode ocorrer em casos de uso excessivo ou inadequado, trauma ou cirurgia, resultando em inflamação local, dor, sensibilização e potencial disfunção. As propriedades mecânicas dos tecidos fasciais, incluindo a sua mobilidade, têm sido avaliadas in vivo através de ecografia. No entanto, este parece ser um método que ainda não está devidamente padronizado nem validado. Objetivos: Identificar, sintetizar e comparar os princípios metodológicos da investigação científica que utilizou a avaliação ecográfica do deslizamento da fáscia profunda em humanos in vivo, e avaliar a sua fiabilidade. Métodos: Realizou-se uma pesquisa sistemática da literatura nas bases de dados ScienceDirect, PubMed (Medline), Web of Science e B-On, de acordo com as diretrizes PRISMA Extension for Scoping Reviews (PRISMA-ScR). A revisão seguiu três etapas principais: (1) identificação da questão e da literatura relevante; (2) seleção da literatura; e (3) agrupamento, mapeamento e resumo dos dados. Critérios de elegibilidade: Foram incluídos os artigos que usaram a ecografia para avaliar o deslizamento da fáscia profunda em seres humanos in vivo, usando o termo “sliding” ou outro com significado semelhante. Foram excluídos os estudos: não disponíveis em publicações revistas por partes, não disponíveis em inglês, português ou espanhol ou cujo texto completo não se encontrava acessível. Resultados: De um total de 104 artigos completos avaliados para elegibilidade, foram incluídos 18 artigos que avaliaram as fáscias profundas das regiões toracolombar (n=4), abdominal (n=7), femoral (n=4) e crural (n=3). Estes estudos abordaram questões de diagnóstico (n=11) e benefícios terapêuticos (n=7) e apresentaram níveis de evidência entre II e IV. Foram usados vários termos para descrever as medidas de resultados correspondentes ao deslizamento fascial. Foram usados diversos posicionamentos dos participantes, procedimentos para induzir o deslizamento fascial e características dos dispositivos de ecografia. Os métodos de análise do deslizamento fascial incluíram a comparação de imagens ecográficas inicial (estado de repouso) e final (estado alvo) e o uso de técnicas de software de correlação-cruzada através de algoritmos de rastreamento automatizado. Estes métodos mostraram-se fiáveis para medir o deslizamento entre a fáscia toracolombar, as junções músculo-fasciais do transverso abdominal, a fáscia lata e a fáscia crural e as fáscias epimisiais adjacentes. No entanto, os artigos incluídos apresentaram terminologias, questões de investigação, populações participantes e metodologias heterogéneas. É escassa a investigação de alta qualidade para determinar a fiabilidade dos métodos atuais para analisar outras fáscias e avaliar a influência da idade, de características relacionadas com o género, composição corporal ou condições clínicas específicas nas medidas de deslizamento fascial. Conclusão: Os métodos ecográficos de medição do deslizamento fascial incluem a comparação entre frames inicial e final de uma gravação de vídeo de ultrassom e a análise de relação cruzada através de algoritmos de rastreamento automatizado. Estes métodos parecem ser fiáveis para medir o deslizamento de algumas fáscias, mas é necessária literatura para confirmar a sua fiabilidade para outras. Além disso, são necessários protocolos de avaliação específicos e padronizados para cada região anatómica, de modo que a avaliação ecográfica do deslizamento fascial in vivo possa ser usada adequadamente na investigação e na prática clínica

Ultrasound Measurement of Local Deformation in the Human Free Achilles Tendon Produced by Dynamic Muscle-Induced Loading: A Systematic Review.

Achilles tendinopathy is the most prevalent lower limb tendinopathy, yet it remains poorly understood, with mismatches between observed structure and reported function. Recent studies have hypothesised that Achilles tendon (AT) healthy function is associated with variable deformation across the tendon width during use, focusing on quantifying sub-tendon deformation. Here, the aim of this work was to synthesise recent advances exploring human free AT tissue-level deformation during use. Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, PubMed, Embase, Scopus and Web of Science were systematically searched. Study quality and risk of bias were assessed. Thirteen articles were retained, yielding data on free AT deformation patterns. Seven were categorised as high-quality and six as medium-quality studies. Evidence consistently reports that healthy and young tendons deform non-uniformly, with the deeper layer displacing 18%-80% more than the superficial layer. Non-uniformity decreased by 12%-85% with increasing age and by 42%-91% in the presence of injury. There is limited evidence of large effect that AT deformation patterns during dynamic loading are non-uniform and may act as a biomarker of tendon health, risk of injury and rehabilitation impact. Better considered participant recruitment and improved measurement procedures would particularly improve study quality, to explore links between tendon structure, function, aging and disease in distinct populations