A utilização de diferentes testes indiretos para avaliar a força muscular dinâmica e a proporção de fibras musculares: uma revisão narrativa

Introdução: Obter informações da força muscular e da proporção de fibras musculares são determinantes para o processo de planejamento e prescrição do treinamento físico. Para mensurar a força muscular e a predominância individual das fibras musculares, são utilizados diferentes tipos de testes, sejam eles considerados padrão ouro ou aqueles que estimam as variáveis indiretamente, apresentando uma validade e confiança aceitáveis na literatura. Objetivo: Explorar e apresentar os métodos e/ou testes indiretos propostos na literatura para estimar a força muscular dinâmica e a predominância de fibras musculares. Materiais e Métodos: Foram utilizadas as bases de dados: US National Library of Medicine National Institutes of Health (PubMed) e Google Acadêmico. Não foram utilizados métodos de busca específicos, apenas estudos que tratavam do tema de pesquisa.  Discussão: Diferentes tipos de testes e/ou métodos indiretos são propostos na literatura que apresentam resultados positivos quando comparados aos testes diretos. Determinando que a utilização destes testes e/ou métodos possam ser úteis na prática de treinadores, atletas e pesquisadores. Conclusão: Considera-se que o teste de uma repetição máxima (1RM) possa ser a melhor alternativa para estimar a força muscular dinâmica. Enquanto para a predominância de fibras musculares, o teste de resistência muscular tem sido apresentado como um potencial método para estimar a proporção de fibras musculares. No entanto, mais estudos são necessários para obtenção de informações concretas acerca da predominância de fibras musculares por meio deste teste

Tensiomyographic assessment of muscle contractile properties in 9- to 14-year old children

While there are numerous data on the skeletal muscle fibre type composition in adults, little is known about the changes in fibre type composition and contractile properties during maturational growth in children. Using noninvasive tensiomyography we measured contraction time, an indirect estimate of the myosin heavy chain I (MHC-I) proportion, to assess the longitudinal changes of the biceps brachii (BB), biceps femoris (BF), vastus lateralis (VL), and erector spinae (ES) muscles in 53 boys and 54 girls. The children were 9 years at the start of the study and returned for 5 follow-up measurements till the age of 14 years. The ES has the shortest and the BF has the longest Tc. The VL and ES of boys have shorter Tc than those from girls. When applying the relationship between proportion of MHC-I and Tc established in adults to the children TMG data, we found a slow-to-fast transition in the VL between at least the age of 6 and 10 years, when it had stabilized to adult proportions. Regular participation in sport was associated with a faster BF, but not in VL. Our data represents a first non-invasive indication of the developmental changes in muscle fiber type composition in children

Hamstrings muscle anatomy and function, and implications for strain injury

The main aim of this thesis was to examine hamstrings anatomy and its influence on knee flexor muscle function in healthy young men. A secondary aim was to better understand the implications of hamstrings anatomy and function, and their variability, in relation to the risk of strain injury. The functional and conventional H:Q ratios (examined up to high angular velocities) as well as the knee joint angle-specific isometric H:Q ratio exhibited good test-retest reliability at joint positions that closely replicated the conditions of high injury risk. Football players did not exhibit any differences in angle-specific or peak torque H:Q ratios compared to recreationally active controls. Knee extensor and flexor strength, relative to body mass, of footballers and controls was similar for all velocities, except concentric knee flexor strength at 400° s-1 (footballers +40%; P < 0.01). Muscle volume explained 30-71% and 38-58% of the differences between individuals in knee extensors and flexors torque respectively across a range of velocities. A moderate correlation was also found between the volume of these antagonistic muscle groups (R2= 0.41). The relative volume of the knee extensors and flexors explained ~20% of the variance in the isometric H:Q ratio and ~31% in the high velocity functional H:Q ratio. Biceps femoris long head exhibited a balanced myosin heavy chain isoform distribution (47.1% type I and 52.9 % total type II) in young healthy men, while BFlh muscle composition was not related to any measure of knee flexor maximal or explosive strength. Biceps femoris long head proximal aponeurosis area varied considerably between participants (>4-fold) and was not related to biceps femoris long head maximal anatomical cross-sectional area (r= 0.04, P= 0.83). Consequently, the aponeurosis:muscle area ratio exhibited 6-fold variability (range, 0.53 to 3.09; CV= 32.5%). Aponeurosis size was not related to isometric or eccentric knee flexion strength. The findings of this thesis suggest that the main anatomical factor that contributes to knee flexors function in vivo is hamstrings muscle size, while muscle composition and aponeurosis size do not seem to have a significant influence. The high inter-individual variability of the biceps femoris long head proximal aponeurosis size suggests that a disproportionately small aponeurosis may be a risk factor for strain injury. In contrast, biceps femoris long head muscle composition does not seem to explain the high incidence of strain injuries in this muscle. Quadriceps and hamstrings muscle size imbalances contribute to functional imbalances that may predispose to strain injury and correction of any size imbalance may be a useful injury prevention tool. Finally, regular exposure to football training and match-play does not seem to influence the balance of muscle strength around the knee joint

Neuromuscular Markers of High Performance Sport Preparation: Muscle Contractile Mechanics

Assessments of skeletal muscle functional capacity or bilateral muscular asymmetry often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated in laboratory settings, as a means to assess muscle contractile function following fatigue; however observations have not been contextualised by concurrent physiological measures. TMG has more sparingly been applied in the field, with elite athletes. The aim of this thesis was to examine acute alterations and underlying variations in muscle contractile mechanics, through the application of TMG, contextualised with established physiological measures; and to apply TMG within high performance sports programmes. TMG successfully detected fatigue, evident from reduced strength, by displaying impaired muscle displacement, accompanied by elevated resting muscle tension. Greater asymmetry was detected in individuals with asymmetric strength; however, symmetry was masked during more complex tasks. Increased day-to-day variability was detected among highly trained athletes compared to recreationally active individuals. Acute training adaptations were detected, in contractile mechanics, in individual muscles. TMG could be useful in establishing fatigue status of skeletal muscle without exacerbating the functional decrements of the muscle, whilst also providing useful screening information for detecting asymmetry which may not be apparent during functional actions

The Effect of Critical Limb Ischaemia on Adult Human Skeletal Muscle

Potential therapeutic avenues may emerge from understanding morphological adaptations of adult human skeletal muscle that result from critical issue ischaemia (CLI). There is little understanding of the role and limitations of satellite cells in repairing and regenerating ischaemic tissue. This study aims to show the pathognomonic changes that take place as adaptations to chronic ischaemia. Patients (n=10) undergoing lower limb amputations for CLI were recruited to the study and gastrocnemius muscle biopsies were compared to those from control patients (n=10) undergoing long saphenous vein harvesting for coronary artery bypass grafting. Transmission Electron microscopy, histology, immunohistochemistry and Western blotting were used to assess the myogenic response to ischaemia. Any significant change in tissue morphology, morphometry and satellite cell number or activity was of interest. There was significantly greater deposition of fibrofatty tissue, collagen and a loss of polygonal structure in CLI samples. Myonuclear number per fibre was not significantly different, neither was the occurrence of centrally occurring nuclei. All fibre types demonstrated significant atrophy except Ilc. Ilc hybrid fibres were more abundant in CLI samples (p=0.0147). Type I fibres displayed a proportionate rise by 2.4 fold (p=0.0288). Type Ilx fibres were most susceptible to ischaemia with x6 fold reduction in number (p=0.0039) and greatest reduction in CSA (p=0.0029). Type II fibres showed greater fibre-size diversity. The endothelial marker, CD31 and the haematopoietic stem cell marker, CD34 were more abundant in CLI (p<0.0001). There was over expression of the satellite cell marker pax? (p<0.0001) and quiescent satellite cell numbers. MyoD, a marker of activated satellite cells is significantly reduced in ischaemia (p<0.0001). These findings confirm active repair and regeneration in CLI tissue, but the indigenous response of muscle is inadequate for proper healing. These processes are disordered, with limited maturation of myogenesis

Evaluation et prise en charge des risques de blessure des ischio-jambiers chez le sprinteur

La déchirure des ischio-jambiers est la blessure non-traumatique la plus fréquemment rencontrée dans les sports demandant une course à haute vitesse. Les ischio-jambiers sont particulièrement vulnérables lors de la fin de phase d'oscillation du sprint étant donné qu'ils se contractent excentriquement alors qu'ils sont en position d'allongement. Le renforcement excentrique a été montré comme étant une méthode efficace pour diminuer le risque de blessure. Cependant, les exercices classiquement utilisés comme le Nordic hamstring ne soumettent pas les ischio-jambiers à un niveau d'allongement spécifique au sprint. Dès lors, l'objectif de cette thèse était d'évaluer le fonctionnement des ischio-jambiers à différents niveaux d'allongement musculo- tendineux puis de transposer dans la pratique les résultats obtenus afin de concevoir des exercices plus spécifiques aux besoins des athlètes. Avant cela, une première partie avait pour but de proposer de nouvelles méthodes d'évaluation de terrain des ischio-jambiers. Les différents travaux réalisés pour cette thèse ont permis : 1) de proposer deux nouveaux outils de terrain pour l'évaluation de la flexibilité et de la force des ischio-jambiers ; 2) de montrer que le niveau d'allongement influence directement la force produite par les ischio-jambiers et de suggérer que ce niveau d'allongement semble être un stimulus au moins aussi déterminant que le mode de contraction musculaire pour générer des adaptations de l'architecture musculaire propices à la diminution du risque de blessure ; 3) de proposer des modalités spécifiques de renforcement des ischio-jambiers destinées aux sprinteurs dans une perspective de prévention des blessures et de montrer l'efficacité de ces recommandations sur l'amélioration d'un certain nombre de facteurs de risque de blessure. Finalement, ce travail a ouvert de nouvelles perspectives allant de la proposition d'exercices de renforcement de terrain au développement d'un système motorisé spécifique au sprint permettant le renforcement et l'évaluation de la force des ischio-jambiers en passant par différents projets de recherche. -- High-speed running sports accounts for the majority of hamstring strains. The terminal swing phase of the running cycle is believed to be the most hazardous as the hamstrings are undergoing an active lengthening contraction in a long muscle length position. Prevention-based strength training relies mainly on eccentric exercises. However, most hamstrings exercises like the Nordic hamstring are performed at an inadequately low hip-flexion angle. Thus, the objective of this thesis was to assess the hamstring function at different muscle lengths and depending on the obtained results to design strength exercises more specific to the athlete's need. Before that, a first part of this thesis aimed to develop new assessment methods of the hamstring on site. The different studies included in the present thesis allowed: 1) to propose two new methods to test the hamstring flexibility and strength on the field; 2) to show that the hamstring muscle length directly influences its level of strength, and to suggest that the training range of motion could be a dominant stimulus (as important than contraction type) for modifying the muscle architecture, which leads to a decrease in hamstring injury risk; 3) to define sprint specific parameters for prevention-based strength training, and to show the efficiency of these recommendations on the improvement of several injury risk factors for the hamstring. Finally, this thesis proposed new perspectives: 1) new strength exercises on site; 2) the development of a motorised device specific for the sprint which could be used to strength and to assess the hamstring; 3) several future research projects

Indicadores de carga de entrenamiento interna, fatiga y estado de bienestar durante el periodo competitivo en jugadoras de fútbol profesional

INTRODUCCIÓN: Para obtener el máximo rendimiento de cada deportista, el entrenamiento debería ser prescrito a cada jugador según sus características individuales y su estado personal. (Impellizzeri, Rampinini, & Marcora, 2005).Además de conocer la carga interna suministrada mediante indicadores objetivos (TRIMP) (Banister,1991) o indicadores subjetivos (RPE) (Foster, 2001) es necesario conocer el tiempo que cada deportista necesita para generar adaptaciones teniendo información en todo momento los estados de fatiga del deportista mediante distintos indicadores como Test Velocidad o estados de Bienestar o recuperación (Hopper, 1995). OBJETIVO: El objetivo de la presente investigación fue conocer la dinámica de los distintos indicadores de carga y fatiga durante un periodo competitivo de un equipo de fútbol femenino profesional español. MÉTODOLOGÍA: La investigación se realizó durante 13 semanas en el periodo de competición en las que hubo partido los fines de semana. Las jugadoras fueron analizadas diariamente (excepto las dos porteras), para ir obteniendo información individualizada en relación a las variables utilizados en la investigación: Test de 10 m, TRIMP, EPF (Foster, 2001), percepción de fatiga general, daño muscula, estrés y sueño propuesta por Hooper (1995)La muestra total obtenida fue una N total de 1514 para las variables registradas. RESULTADOS: El RPE, en la muestra estudiada, resultó ser un método útil al mostrar una correlación muy alta (r=0,70; p<0,05) con un método basado en la frecuencia cardiaca. La carga de entrenamiento de partido fue superior a la carga del entrenamiento de las jugadoras que no jugaron para compensar (r=0,85; p<0,01). Se encontraron diferencias en las variables relacionadas con la fatiga el día -4 posterior a partido, entre las jugadoras que jugaron partido y las que hicieron el entrenamiento compensatorio. Se encontraron diferencias significativas los distintos días de la semana de competición entre las variables relacionadas con la carga y fatiga. CONCLUSIONES: Se podrían utilizar valores de fatiga y carga como referencia de cada sesión de la semana al comprobar que cada día los valores son diferentes. La carga del entrenamiento compensatorio es muy inferior a la del partido, por lo que los jugadores suplentes podrían estar recibiendo estímulos incompletos. El día -4, que es el primer día de la semana de carga alta ya que se suele pensar que la recuperación se ha completado, las jugadoras que jugaron el partido el día anterior y las que fueron suplentes no están todavá en el mismo estado de recuperación