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Abstract

This study compared the effects of concentric and eccentric training on neuromuscular adaptations in young subjects. Twenty-two men and women were assigned to one of two groups: concentric (CON, n = 11) and eccentric (ECC, n = 11) training. Training consisted of 6 weeks of isokinetic exercise, performed twice weekly, starting with two sets of eight repetitions, and progressing to five sets of 10 repetitions. Subjects were tested in strength variables [concentric, eccentric, and isometric peak torque (PT), and rate of force development (RFD)], muscle conduction velocity (CV), neuromuscular activity, vastus lateralis (VL) muscle thickness, and echo intensity as determined by ultrasonography. There were similar increases in the concentric and eccentric PTs in both the CON and ECC groups (P < 0.01), but only the ECC group showed an increase in isometric PT (P < 0.001). Similarly, both groups exhibited increased VL muscle thickness, CV, and RFD, and reduced VL echo intensity (P < 0.05). Significant correlations were observed among the relative changes in the neuromuscular outcomes and training variables (e.g., total work, average PT) (r = 0.68-0.75, P < 0.05). The results showed that both training types similarly improved dynamic PT, CV, RFD, and muscle thickness and quality during the early weeks of training.

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... Therefore, the present study implemented HIIT based on whole-body training for its applicability to the general population. Muscular morphology has been reported to be associated with muscular power [11], muscular strength [12,13] and cardiovascular fitness [11]. Furthermore, ultrasonography has been determined to be an accurate and reliable technique to measure muscle morphology [14]. ...
... Furthermore, ultrasonography has been determined to be an accurate and reliable technique to measure muscle morphology [14]. Ultrasonography is a popular tool to determine muscle cross-sectional area (mCSA) and echo intensity (EI), which indicate the quantity and quality of muscle mass, respectively [12,13]. Muscle quality can be assessed by EI, which estimates the amount of contractile (i.e., muscle fibers) and non-contractile (i.e., adipose, connective tissue) components of muscle tissue [15,16]. ...
... Muscle quality can be assessed by EI, which estimates the amount of contractile (i.e., muscle fibers) and non-contractile (i.e., adipose, connective tissue) components of muscle tissue [15,16]. In addition, several studies have demonstrated the effects of resistance training on mCSA [17,18] and EI [12,18], but few studies have investigated the muscular morphological adaptations of HIIT. ...
Article
Background: High-intensity intermittent training (HIIT) has increased in popularity due to being time-efficient mode of exercise. Previous HIIT studies have mainly focused on percentage of fat loss, fat mass loss, and weight loss. However, enhancing muscle protein synthesis induced by HIIT that results in muscular morphological adaptations is a potential benefit of HIIT. This study compared the effects of two HIIT protocols on muscular morphological adaptations. Methods: Thirty-four recreationally active participants were randomly assigned to 10-5-HIIT and 20- 10-HIIT to complete 6 sets of 6 intervals. The 10-5-HIIT and 20-10-HIIT protocols were performed with 10s:5s and 20s:10s exercise-to-rest ratios and provided with 1- and 2-min recovery periods between sets, respectively. Muscle cross-sectional area (mCSA) and echo intensity (EI) of the rectus femoris (RF) and vastus lateralis (VL) were assessed via B-mode ultrasonography before and after intervention. Two-way mixed factorial ANOVAs were used for analyses. Results: The 10-5-HIIT and 20-10-HIIT groups significantly (p < 0.05) increased RF mCSA (change (Δ) = 0.4 ± 0.8 cm2, 8.0%; Δ = 0.5 ± 0.8 cm2, 5.5%) and VL mCSA (Δ = 1.2 ± 1.6 cm2, 9.0%; Δ = 2.20 ± 1.4 cm2, 10.4%), respectively. No significant (p > 0.05) change was observed for the EI of the RF and VL. Conclusions: Whole-body HIIT can be a time-efficient exercise modality to elicit muscular morphological adaptations in the RF and VL muscles. The 10-5-HIIT protocol induced benefits comparable to those of the 20-10-HIIT, while it reduced the total exercise time by 50%.
... Conventional resistance training exercises, such as the squat and deadlift, are efficacious in improving muscular strength, however they are limited by the amount of mass the athlete is able to lift in the concentric phase. Conversely, humans are able to produce greater magnitudes of force during eccentric movements [5], and training strategies that afford an overload of eccentric muscle actions are potentially more efficacious than traditional resistance training [6][7][8], particularly for athletes with a long training history who might be limited in their potential to adapt to traditional resistance training methods [9][10][11]. The potential novelty offered by eccentric training strategies, coupled with the potential to elicit higher muscular forces than traditional training, makes such approaches attractive to well-trained athletic populations. ...
... The application of high-intensity eccentric training is efficacious at improving strength, likely to a greater extent than concentric training as first demonstrated by Bradenburg & Docherty [12], however few studies have adopted an ecologically valid training approach. Following habitual use of high-intensity eccentric exercise there is evidence of increased maximum force producing capacity during eccentric, concentric and isometric exertions [6,13], and numerous studies support the superiority of eccentric vs concentric training in eliciting improvements in measures of strength [6,8,[13][14][15]. The majority of these studies employed isokinetic and/or single joint eccentric exercise, whereas in practice athletes typically perform multi-joint, compound movements. ...
... The training intensity experienced by the AEL and AEL-ATH groups was 23-30% higher during the leg press exercise, because of the progressive overload of the eccentric phase of the exercise. Previous work has typically programmed load for the eccentric phase relative to concentric strength [16,17,25,26], whereas the approach adopted here allowed for the exploitation of the greater force producing capacity associated with eccentric muscle actions [5,6,8], whilst accounting for individual differences in eccentric strength. The optimal prescription of augmented eccentric load is unknown, but this range could provide a suitable guideline for those practitioners that do not have access to equipment that facilitates the safe evaluation of eccentric-specific strength. ...
Article
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This study assessed the efficacy of strength training using augmented eccentric loading to provoke increases in leg strength in well-trained athletes, and sprint track cyclists, using a novel leg press device. Twelve well-trained athletes were randomly allocated traditional resistance training (TRAD, n = 6), or resistance training using augmented eccentric loading (AEL, n = 6). A further 5 full-time, professional sprint track cyclists from a senior national squad programme also trained with augmented eccentric loading (AEL-ATH) alongside their usual sport-specific training. Participants completed four weeks of twice-weekly resistance training using the leg press exercise. In TRAD the lowering phase of the lift was set relative to concentric strength. In AEL and AEL-ATH the lowering phase was individualised to eccentric strength. Concentric, eccentric, isometric and coupled eccentric-concentric leg press strength, and back squat 1 repetition maximum (1RM), were assessed pre- and post-training. The AEL and AEL-ATH groups performed the eccentric phase with an average 26 ± 4% greater load across the programme. All groups experienced increases in concentric (5%, 7% and 3% for TRAD, AEL & AEL-ATH respectively), eccentric (7%, 11% and 6% for TRAD, AEL & AEL-ATH respectively), and squat 1RM (all p < 0.05), where the AEL-ATH group experienced relatively greater increases (13% vs. 5% in TRAD and AEL, p < 0.01). The TRAD and AEL groups also increased isometric strength (p < 0.05). A four-week period of augmented eccentric loading increased leg strength in well-trained athletes and track cyclists. The eccentric leg press stimulus was well-tolerated, supporting the inclusion of such training in the preparation programmes of athletes.
... Only one study did not mention the age of subjects (Mendiguchia et al., 2020). Some participants engaged in recreational physical activity (Coratella et al., 2015;Timmins et al., 2016;Bourne et al., 2017;Seymore et al., 2017;Alonso-Fernandez et al., 2020;Marusic et al., 2020;Presland et al., 2020) moderate physical activity (Ribeiro-Alvares et al., 2018;Abián et al., 2020), and others were physically active (Cadore et al., 2014;Mendiguchia et al.;Timmins et al., 2021). In four studies, the subjects' physical activity level is not mentioned (Guilhem et al., 2013;Franchi et al., 2014;Sanz-López et al., 2016. ...
... Fourteen studies evaluated the effects of eccentric training on FL. Significant increases in FL were found in 12 studies, six of which Mendiguchia et al.;Ribeiro-Alvares et al.;Timmins et al., 2016Timmins et al., , 2021Marusic et al.) performed NHE strength training, five performed isokinetic eccentric strength training (Franchi et al.;Cadore et al.;Coratella et al.;Marzilger et al., 2019Marzilger et al., , 2020 and one completed flywheel training with an additional eccentric bias (Presland et al.). ...
... of modifying muscle architecture parameters generating an increase in FL and MT, and a decrease in PA (Guilhem et al.;Marzilger et al., 2020;Abián et al.;Coratella et al.;Cadore et al.). ...
Article
LIZAMA-PÉREZ, R.; CHIROSA-RIOS, I.; CHIROSA-RIOS, L.; OLAVE; E.; FERRAGUT, C.; VILA, H. & JEREZ-MAYORGA, D. Effects of eccentric exercise on muscle architecture in adults: A systematic review. Int. J. Morphol., 40(2):425-432, 2022. SUMMARY: The purpose of this systematic review was to determine the effects of eccentric training on muscle architecture in the adult population. Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statements were followed using keywords associated with architecture muscular and eccentric training. Four databases were used: PubMed, Scopus, SPORTDiscus and Web of Science. Methodological quality was assessed using the PEDro scale. A total of 1260 articles were retrieved, 18 included in this review. The parameters most frequently evaluated in the studies consulted were pennation angle (PA), fascicle length (FL), and muscle thickness (MT). These were assessed mainly in lower limb muscles such as biceps femoris long head (BFlh), vastus lateralis (VL), medial gastrocnemius (MG) and lateral gastrocnemius (LG), respectively. Eccentric training for at least four weeks generates adaptations in these parameters, mainly by increasing MT with FL and decreasing PA, determining muscle function. These results provide evidence on the effects of eccentric training on muscle architecture, which could be helpful to prevent injuries and favor muscle recovery processes.
... [1][2][3][4] It is widely accepted that muscular strength and power are determined by the structural characteristics and composition of the musculature involved in the targeted exercise and that higher muscle quality may produce greater force and power. 3,5,6 By contrast, increased body fat content is considered to be a performance-limiting factor. Both intramuscular and subcutaneous adipose tissue (SAT) have been reported as detrimental to performance, and high-level athletes often maintain extremely low body weight and/or fat mass in an attempt to gain a competitive advantage. ...
... 15 Ultrasound imaging is a reliable tool for the assessment of muscle quality in different populations, including athletes, and in the sport-related environment, and represents a new field of application. 5,6 Simultaneous evaluation of body composition and muscle quality may provide additional insights into an athlete's physical condition and may help to support choices about training and nutrition. ...
... p=0.04) [6] and greater EI values in the VL of injured compared with healthy basketball players. 27 Early adaptive changes in strength and muscle architectural variables found after concentric or eccentric isokinetic exercise training were accompanied by significant increases in muscle quality such as a decrease in EI. 5 Significant improvements in muscle quality (i.e., decreases in EI) after both low-and highvolume strength training in older people were shown to be accompanied by increases in maximal strength. 28 Observations of elderly populations have shown that increases in physical performance and muscle quality (i.e., decreases in EI) and reduction in intramuscular adipose tissue content are associated with changes in muscle composition such as increases in number and size of contractile units and/or decreases in nonfunctional connective tissue. ...
Article
Background: Many variables are considered to be determinants of cycling sprint performance. Among them, the importance of skeletal muscle properties in relation to cycling performance has been consistently underlined. The aim of the present study was to evaluate the vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM), echo intensity (EI) and subcutaneous adipose tissue (SAT) content in a group of competitive cyclists and to identify whether these are related to sprint performance. Methods: Muscle echo intensity was evaluated by ultrasound in 16 highly trained competitive cyclists. The cyclists performed a maximal-intensity sprint session comprising four 15 s maximal sprints on a Wingate bike with 2 min of recovery between each. Pearson correlational analysis with linear regression was used to identify significant relationships between the criteria EI and SAT content and the sprint performance variables. Results: Muscle EI correlated strongly with sprint performance markers (r = from 0.54 to 0.62; p<0.05), while SAT content and body fat percentage correlated trivially to moderately with sprint performance (r = from 0.07 to 0.40; p>0.05). Conclusions: Overall, muscle quality of knee extensors was positively related to sprint performance markers, but SAT content was not. Although additional studies are needed, muscle quality may represent a valid body composition indicator and may be helpful for supporting sprint performance optimization procedures in competitive cyclists.
... Conforme Barroso et al. (2005),a atividade neuromuscular apresenta aspectos distintos, indo além das características mecânicas inerentes a cada ação. As ações isométricas e concêntricas apresentam uma atividade elétrica muito maior comparada a ações excêntricas em testes de eletromiografia e que essas duas com atividades mais altas apresentam uma correlação elevada e linear com a força muscular produzida, já nas ações excêntricas o sinal é menor para os mesmos níveis de força, sejam eles absolutos ou relativos, quando comparados a ações concêntricas ou isométricas, o que indica que há uma menor ativação elétrica do músculo(CADORE et al., 2014; BARROSO et al., 2005;GUILHEM et al., 2010). ...
... Uma das hipóteses usadas para explicar a hipertrofia é a relação com o nível do dano muscular causado pelo treinamento(BARROSO et al., 2005).As estruturas do músculo tem a capacidade de se regenerar frente a grandes níveis de dano muscular induzidos pelo exercício e, consequentemente, adaptar-se (TORRES; DUARTE, 2005). As ações excêntricas são conhecidas por causar maior dano muscular (GAULT;WILLEMS, 2013; BARROSO et al., 2005;CADORE et al., 2014), estudos tem proposto que alongamento combinado com sobrecarga são o estimulo mais efetivo para o crescimento muscular, as ações excêntricas são compostas por estes dois parâmetros configurando então um maior dano muscular (HEDAYATPOUR; FALLA, 2015). A hipertrofia é fundamentada na hipótese da ativação de células satélites, que supostamente estariam mais ativas após ocorrer dano às estruturas musculares(BARROSO et al., 2005). ...
... Estes achados implicam no conceito de especificidade, onde as adaptações são dependentes da forma com o que os exercícios são realizados, ações excêntricas aumentam a força excentricamente, enquanto as concêntricas aumentam concentricamente, como é evidenciado nesse estudo acima citado. Em outro estudo conduzido porCadore et al. (2014), onde foi realizado treinamento com ações excêntricas e concêntricas durante 6 semanas, avaliaram-se parâmetros de força como pico de torque máximo excêntrico, concêntrico e isométrico, também avaliou atividade neuromuscular máxima, velocidade de condução do sinal e alguns parâmetros de hipertrofia. Destarte, os resultados mostraram que ambos os treinos induziram adaptações similares para força muscular concêntrica e excêntrica, porém na força muscular isométrica houve um aumento significativo somente com treinamento excêntrico, na velocidade de condução do sinal também houve um aumento significativo pelo treinamento de ambas as ações musculares, como representada na tabela 1.Fonte: Cadore et al. (2014).4 ...
... Conforme Barroso et al. (2005),a atividade neuromuscular apresenta aspectos distintos, indo além das características mecânicas inerentes a cada ação. As ações isométricas e concêntricas apresentam uma atividade elétrica muito maior comparada a ações excêntricas em testes de eletromiografia e que essas duas com atividades mais altas apresentam uma correlação elevada e linear com a força muscular produzida, já nas ações excêntricas o sinal é menor para os mesmos níveis de força, sejam eles absolutos ou relativos, quando comparados a ações concêntricas ou isométricas, o que indica que há uma menor ativação elétrica do músculo(CADORE et al., 2014; BARROSO et al., 2005;GUILHEM et al., 2010). ...
... Uma das hipóteses usadas para explicar a hipertrofia é a relação com o nível do dano muscular causado pelo treinamento(BARROSO et al., 2005).As estruturas do músculo tem a capacidade de se regenerar frente a grandes níveis de dano muscular induzidos pelo exercício e, consequentemente, adaptar-se (TORRES; DUARTE, 2005). As ações excêntricas são conhecidas por causar maior dano muscular (GAULT;WILLEMS, 2013; BARROSO et al., 2005;CADORE et al., 2014), estudos tem proposto que alongamento combinado com sobrecarga são o estimulo mais efetivo para o crescimento muscular, as ações excêntricas são compostas por estes dois parâmetros configurando então um maior dano muscular (HEDAYATPOUR; FALLA, 2015). A hipertrofia é fundamentada na hipótese da ativação de células satélites, que supostamente estariam mais ativas após ocorrer dano às estruturas musculares(BARROSO et al., 2005). ...
... Estes achados implicam no conceito de especificidade, onde as adaptações são dependentes da forma com o que os exercícios são realizados, ações excêntricas aumentam a força excentricamente, enquanto as concêntricas aumentam concentricamente, como é evidenciado nesse estudo acima citado. Em outro estudo conduzido porCadore et al. (2014), onde foi realizado treinamento com ações excêntricas e concêntricas durante 6 semanas, avaliaram-se parâmetros de força como pico de torque máximo excêntrico, concêntrico e isométrico, também avaliou atividade neuromuscular máxima, velocidade de condução do sinal e alguns parâmetros de hipertrofia. Destarte, os resultados mostraram que ambos os treinos induziram adaptações similares para força muscular concêntrica e excêntrica, porém na força muscular isométrica houve um aumento significativo somente com treinamento excêntrico, na velocidade de condução do sinal também houve um aumento significativo pelo treinamento de ambas as ações musculares, como representada na tabela 1.Fonte: Cadore et al. (2014).4 ...
... One of the electromyographic variables that has made it possible to describe possible effects generated by eccentric exercise in muscles is the muscle fibre conduction velocity (MFCV), defined as the speed at which an action potential is propagated through the sarcolemma of a musculoskeletal fibre 13 . This variable reflects possible peripheral muscle changes, as the product of exhaustion 13 , a pathology associated with the musculoskeletal system 14,15 , or the effect of eccentric exercise 16,17 . According to this latter point, some research has reported a modification of the MFCV against its baseline levels after applying a protocol of eccentric contractions, considering different muscles and eccentric exercise protocols 9,11,18 . ...
... Five studies used isokinetic machines to develop eccentric exercise protocols, considering the biceps brachii 9,11,18 and vastus lateralis 16,20 muscles. On the other hand, only one study used the "leg press" machine to induce eccentric muscle damage in the vastus lateralis and vastus medialis obliquis 19 . ...
... Regarding the magnitude of the ROM used over the elbow joint, the contractions were made between 65°-175º 9,11,18 . As for the eccentric exercise protocols for the quadriceps (vastus lateralis and medialis), two studies applied different loads to induce muscle damage 16,19 and only one study developed eccentric contractions up to exhaustion 20 . Out of these three studies, one of them applied an eccentric contractions intervention 19 , another generated randomised exposures of exhausting dynamic contractions 20 , and the last one carried out a training programme with eccentric contractions for six weeks 16 . ...
Article
Full-text available
Introduction: According to the literature, eccentric exercise has been considered a precursor of neuromuscular changes generated by post-exercise damage, mainly causing an alteration in the muscle cell membrane. Muscle fiber conduction velocity (MFCV) has been one of the physiological variables that have allowed to quantify this alteration. Some investigations have shown a decrease in the MFCV after eccentric exercise protocols; however, few studies have confirmed these findings. This review aimed to describe the recent scientific evidence that reports changes in the MFCV after eccentric exercise protocols. Material and method: From 265 articles, 6 articles were selected from EBSCO and MEDLINE platforms with a temporal filter of 10 years (between 2010 and April 2020), using inclusion/exclusion criteria predetermined. Firstly, the information from eccentric exercise effect on MFCV, and exercise protocols were described. Secondly, the techniques used to record electromyographic signals and some criteria to determine the MFCV were reported. Results: Modifications of MFCV can be observed after eccentric exercise in almost all selected articles. At the same time, a decrease of this variable was observed in four studies, associated with the biceps brachii and two portions of the quadriceps muscles. However, one article describes an increase of the MFCV in the vastus lateralis quadriceps. Conclusion: The articles suggest that eccentric contractions could modify the MFCV behavior of some muscles. However, evidence is still lacking to describe the real cause of these changes. // Introducción: Según la literatura, el ejercicio excéntrico ha sido considerado como un precursor de cambios neuromusculares generado por el daño post-ejercicio, causando principalmente una alteración en la permeabilidad de la membrana celular muscular. Una de las variables fisiológicas que ha permitido cuantificar esta alteración, es la velocidad de conducción de la fibra muscular (VCFM). Algunas investigaciones han mostrado una disminución de esta variable posterior a protocolos de ejercicio excéntrico; sin embargo, existen pocos estudios que confirmen este hallazgo. Este estudio tuvo como objetivo describir la evidencia científica reciente que reporte cambios en la VCFM después de protocolos de ejercicio excéntrico. Material y método: De 265 artículos, se seleccionaron 6 artículos de las plataformas EBSCO y MEDLINE con un filtro temporal de 10 años (entre 2010 y abril de 2020), usando criterios de inclusión/exclusión predeterminados. En primer lugar, se describió el efecto del ejercicio excéntrico sobre la VCFM y los protocolos de ejercicios. Secundariamente, se reportaron las técnicas utilizadas para registrar la señal electromiográfica, y algunos criterios para determinar la VCFM. Resultados: Es posible observar modificaciones de la VCFM luego del ejercicio excéntrico en casi todos los artículos selecciona-dos. Al mismo tiempo, se observa una disminución de esta variable en cuatro estudios, asociado a los músculos bíceps braquial y dos porciones del cuádriceps. Sin embargo, un artículo describe un incremento de la VCFM en el vasto lateral del cuádriceps. Conclusión: Los artículos sugieren que las contracciones excéntricas podrían modificar el comportamiento de la VCFM de algunos músculos. Sin embargo, aún falta evidencia para describir la real causa de estos cambios.
... Only one study did not mention the age of subjects (Mendiguchia et al., 2020). Some participants engaged in recreational physical activity (Coratella et al., 2015;Timmins et al., 2016;Bourne et al., 2017;Seymore et al., 2017;Alonso-Fernandez et al., 2020;Marusic et al., 2020;Presland et al., 2020) moderate physical activity (Ribeiro-Alvares et al., 2018;Abián et al., 2020), and others were physically active (Cadore et al., 2014;Mendiguchia et al.;Timmins et al., 2021). In four studies, the subjects' physical activity level is not mentioned (Guilhem et al., 2013;Franchi et al., 2014;Sanz-López et al., 2016. ...
... Fourteen studies evaluated the effects of eccentric training on FL. Significant increases in FL were found in 12 studies, six of which Mendiguchia et al.;Ribeiro-Alvares et al.;Timmins et al., 2016Timmins et al., , 2021Marusic et al.) performed NHE strength training, five performed isokinetic eccentric strength training (Franchi et al.;Cadore et al.;Coratella et al.;Marzilger et al., 2019Marzilger et al., , 2020 and one completed flywheel training with an additional eccentric bias (Presland et al.). ...
... It has already been possible to determine the effects of isokinetic eccentric exercise on quadriceps muscle mass and strength in a population before or after ACL reconstruction or meniscectomy (Zhang et al., 2017;Vidmar et al., 2019Vidmar et al., , 2020, its effect on neural adaptations has also been seen (Barrué-Belou etal., 2016). The results of this review support its use as a potential way of modifying muscle architecture parameters generating an increase in FL and MT, and a decrease in PA (Guilhem et al.;Marzilger et al., 2020;Abián et al.;Coratella et al.;Cadore et al.). ...
... Ainda, a espessura do quadríceps também não apresentou relação com a velocidade preferida de marcha em seis metros em mulheres idosas (RECH et al., 2014). (REEVES et al., 2009;CADORE et al., 2014;VÁCZI et al., 2014;DIAS et al., 2015;LASTAYO et al., 2017). ...
... O treinamento puramente concêntrico tem como resultado principal um aumento no ângulo de penação das fibras musculares (relacionado ao aumento dos sarcômeros -ou das miofibrilas -em paralelo), gerando também um aumento da espessura muscular e um aumento na área de secção transversa (CADORE et al., 2014;FRANCHI et al., 2015;WISDOM;DELP;KUHL, 2015;TIMMINS et al., 2016). Já o treino excêntrico, além do efeito em paralelo, gera aumento no comprimento dos fascículos musculares (decorrente do aumento do número de sarcômeros em série em cada miofibrila -ou hipertrofia em série) (REEVES et al., 2009;FRANCHI et al., 2015;TIMMINS et al., 2016). ...
... Diante das adaptações citadas na arquitetura muscular, a partir do treinamento de força (REEVES et al., 2009;CADORE et al., 2014;VÁCZI et al., 2014;DIAS et al., 2015;LASTAYO et al., 2017) ...
Article
Full-text available
O envelhecimento do corpo acarreta alterações na arquitetura muscular, com consequente efeito deletério sobre a capacidade funcional e independência de idosos. Compreender como os parâmetros de arquitetura muscular interferem na funcionalidade do músculo esquelético, especialmente em idosos, é de fundamental importância para os profissionais da saúde que trabalham em processos de treinamento e reabilitação. O objetivo deste estudo é realizar uma revisão narrativa sobre os parâmetros e as adaptações na arquitetura muscular no envelhecimento e as implicações na funcionalidade de pessoas idosas. A arquitetura muscular afeta a funcionalidade do músculo esquelético, conforme a disposição das fibras musculares, em relação ao eixo de geração de força. A melhora na arquitetura muscular reflete-se em um melhor desempenho em tarefas funcionais e na independência dos idosos nas atividades de vida diárias. O treinamento de força é efetivo para minimizar os efeitos deletérios do envelhecimento na arquitetura muscular e reduzir os impactos negativos na capacidade funcional.
... Echo intensity is determined by drawing a region of interest on the ultrasound image without including subcutaneous fat or bone. This region of interest may be a pre-specified sized box [3, 31, 33, 36, 40, 42, 48-51, 53, 54], a box containing as much of the muscle as possible [4,7,8,10,20,23,24,27,35,37,57,58], or free hand tracings between the adipose tissue and bone [9,15]. The majority of studies on echo intensity use a scale between 0 (black) and 255 (white) [4,20,24] or 0 (black) to 256 (white) [29,31,34]. ...
... This region of interest may be a pre-specified sized box [3, 31, 33, 36, 40, 42, 48-51, 53, 54], a box containing as much of the muscle as possible [4,7,8,10,20,23,24,27,35,37,57,58], or free hand tracings between the adipose tissue and bone [9,15]. The majority of studies on echo intensity use a scale between 0 (black) and 255 (white) [4,20,24] or 0 (black) to 256 (white) [29,31,34]. However, other studies use a reverse scale ranging from 0 (white) to 100 (black) [14,16,19]. ...
... Although echo intensity is used as a marker for changes in muscle quality [7][8][9][10][20][21][22][23][24][25][26][27], studies using changes in echo intensity as a proxy have produced inconsistent results following resistance training (Table 1). Echo intensity has been reported to decrease [7, 20-24, 26, 27, 46], increase [25,27,57], or remain unchanged [8-10, 21, 27, 44-46, 64] following repeated bouts of resistance exercise. ...
Article
Echo intensity is the mean pixel intensity of a specific region of interest from an ultrasound image. This variable has been increasingly used in the literature as a physiological marker. Although there has been an increased interest in reporting changes in echo intensity in response to exercise, little consensus exists as to what a change in echo intensity represents physiologically. The purpose of this paper is to review some of the earliest, as well as the most up to date literature regarding the changes in echo intensity in response to exercise. Echo intensity has been used to measure muscle quality, muscle damage, acute swelling, and intramuscular glycogen. The changes in echo intensity, however, are not consistent throughout the literature and often times lead to conclusions that seem contrary to the physiologic effects of exercise. For example, echo intensity increases in conjunction with increases in strength, contrary to what would be expected if echo intensity was a marker of muscle quality/muscle damage. It is conceivable that a change in echo intensity represents a range of physiologic effects at different time points. We recommend that these effects should be determined experimentally in order to rule out what echo intensity might and might not represent. Until this is done, caution should be employed when interpreting changes in echo intensity with acute and chronic exercise.
... As hypothesised, increases in upper-and lower-body muscular strength were significantly greater in EXP than CON. Interestingly, the increases in strength observed in both upper and lower body measures in the current investigation were greater than previous investigations (Cadore et al., 2014;Koutedakis and Jamurtas, 2004;Van Marken Lichtenbelt et al., 1995). Additionally, there were no differences between groups in either VJ height or power, however EXP experienced a greater magnitude of change in VJ power than CON. ...
... However, limitations in a collegiate setting, such as university-imposed recess as well as academic and performances schedules, make implementation of long-term studies difficult. Though not examined in the current study, Cadore et al. (2014) have reported an improvement in muscle quality from strength training (i.e. decreased intramuscular connective and adipose tissue) even with minimal changes in muscle size. ...
Article
Although weight training can enhance muscular strength, power, and body composition, outdated beliefs about muscular adaptations have limited its use in dancers. The purpose of this study was to investigate the effect of an 8-week progressive overload resistance-training (RT) program on muscular strength, power and body composition in collegiate female dancers. Sixteen subjects were randomised into a dance-only control group (CON) or an RT + dance training group (EXP). EXP met 3×/week for RT. Body fat (%BF), lean body mass (LBM), girth measurements, vertical jump (VJ), muscular strength (1-repetition max (RM) squat (SQT) and 1-RM bench press (BP)), maximal oxygen consumption (V̇O 2max , and ventilatory threshold (VT)) were assessed pre- and post-study. Baseline performance characteristics across all subjects were: %BF=28.2±5.7%, VJ=33.4±5.4 cm, SQT=57.5±12.1 kg, BP=30.1±7.6 kg, (V̇O 2max )=40.6±3.4 ml/kg/min, and VT=71.2±3.4%VO 2max . Strength improvements were significantly greater for EXP than CON (P<0.05). No significant differences were found between groups for %BF, LBM, girth measurements, VJ height , (V̇O 2max ), or VT (P>0.05). However, a trend was observed for VJ power favouring EXP (P=0.07). EXP significantly improved strength, while no significant changes were observed in body composition. However, EXP improved their power-to-weight ratio, which may be a positive performance adaptation. RT for dancers can improve strength and power, allowing enhanced muscular loading and fatigue-resistance, which may optimise performance and decrease injury risk.
... Anthropometric parameters like body mass, body mass index (BMI) are associated with health problems such as cardiovascular pathology, diabetes, cancer [23]. Changes of muscle characteristics are related to muscle strength [24]. BMI can be used for personnel selection according to physical fitness abilities, but in some cases BMI does not relate with military performance [25,26]. ...
... Analysis of anthropometric characteristics showed that BMI changes were in the interval from 21.34 to 33. 24 value over the standards by 20% (28-30 for males and 26-28 for females). For 11.9% (5 males and 2 females) of respondents BMI value was over the standards by 30% (over 30 for males and over 28 for females) (Fig. 3). ...
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High standards of physical ability and health are essential for Military personnel and its career. Training of military personnel in field conditions is an essential process. The aim of the study was to evaluate readiness of cadets to high physical load during the combat training course (CTC). We carried out the following: evaluated posture status, analysed anthropometric characteristics, controlled parameters of musculoskeletal system such as muscle tone, muscle strength characteristics, and provided Nordic Questionnaire list containing a figure of Human Body, where a respondent marked the regions of musculoskeletal disorder (pain). All subjects gave their informed consent to the protocol approved by the local Medical Ethics Committee of Rıga Stradiņš University for biomedical research. Combat training course has duration of ten days and includes various physical, tactical, and psychological activities in military conditions that are a compulsory part of study process in National Defence Academy of Latvia. Cadets are facing complex challenges in tactical situations where they can approve their physical abilities, endurance and psychological persistence. They have dietary and sleeping deprivation during the course. We provided standardized Nordic Questionnaire for analysis and evaluation of musculoskeletal disorders in the study group and indicated main problematic regions with musculoskeletal symptoms. The general health status of participants was checked by medical specialists in military Medical Centre and advanced examination was done by Sports medicine doctor. The aim of the study is to analyse the posture status, foot status, to make muscle functional tests that allow managing pre-courses training program for CTC participants and optimizing adaptation of participants of the course to field condition of military training. Evaluating musculoskeletal symptoms cadets indicated that main problematical regions were lower back and knee. In 77% (42/54) of cases cadets with lower limb hyper-tonus had asymmetric posture in frontal plane. Analysis of anthropometric characteristics showed that body mass index changes were in the interval from 21.34 to 33.24. BMI value for 32.2% of participants corresponded to the standards of WHO recommendations. Analysis of posture and foot status was important for provision of preventive measures and reduction of the risk of health disorders related to high physical load in military environment. Persons with expressed asymmetry of posture and foot during dynamic load and static load can have overstress with high risk of health disorders, musculoskeletal pathology and psychological overload.
... 27,29,39,52 Regarding the EI of the muscle, there is an increase in intramuscular connective tissue and a decrease in the number of capillaries in aging. These changes will contribute to greater isolation of each capillary from the adjacent muscle fiber and reduced blood supply to muscle fibers, 40,53 which may explain the increase in muscle echo-intensity in inactive older adult people. ...
... Studies show that regular exercise leads to an increase in muscle vascularization, attenuating the effects of aging, which explains the decrease in muscle EI. 29,40,53 Thus, the significant decrease in the EI of the right RF and VL and the left VM and VL muscles observed in this study after the physical intervention agrees with what is described in the literature, demonstrating, once again, that physical exercise attenuates the effects of aging and also that it brings benefits for many diseases and health disorders, including sarcopenia. 27 However, this study did not find significant differences in MT, which is often suggested by the literature. ...
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INTRODUCTION: Population aging has become an increasing challenge in society and inactive aging populations are especially challenging. OBJECTIVE: The main aim of this study is to conduct ultrasound evaluation of the effects of an intervention program on muscle architecture in older adults. METHODS: A total of thirty-four individuals of both sexes aged over 60 years were divided into two groups as follows: an intervention group (n = 18), who took part in a physical activity program for 8 weeks, three sessions per week, lasting approximately 20 min on each occasion, and a control group, whose members were encouraged to maintain their usual daily routines (outdoor aerobic exercise) (n = 16). Only six of the 18 participants from the intervention group were available for a second evaluation session. All the participants were submitted to bilateral quadriceps muscle ultrasound evaluations; thickness and echo-intensity of muscles were analyzed. RESULTS: Muscle thickness showed a significant negative correlation with age and echo-intensity showed a significant positive correlation with age. Echo-intensity showed a significant negative correlation with muscle thickness. Comparing the groups at the baseline evaluation, there were no significant differences between them (p < 0.05) for either measurement. CONCLUSIONS: We can highlight three points regarding post-intervention status in the intervention group: 1. There were significant differences in echo-intensity. It is therefore essential to establish early strategies to promote active aging, thus preventing dependence and inactivity in the older adult population; 2. Ultrasound is a good method for evaluating the musculoskeletal system and its changes in response to aging and physical activities; 3 Physical activities are important to maintain the muscles healthy and the older adult population independent.
... The present study showed no significant changes in the muscle EI in response to both sprint protocols. An increase in the muscle EI after eccentric exercise bouts has been observed in different investigations (Chen et al., 2011;Cadore et al., 2014). Regarding biceps femoris EI, Chen et al. (2011) found significant increases in this muscle and no changes in quadriceps femoris in response to maximal eccentric contractions. ...
... Regarding biceps femoris EI, Chen et al. (2011) found significant increases in this muscle and no changes in quadriceps femoris in response to maximal eccentric contractions. However, it is difficult to compare their outcomes with the present results because they used pure eccentric muscle actions performed in isokinetic devices (Chen et al., 2011;Cadore et al., 2014) whereas in the present study we assessed the EI after a cyclic multi-joint ballistic exercise, such as running at maximal speed. The absence of changes in these variables in the present study may be due to the training background of our participants, who often perform sprint exercises during their regular workouts and during their games. ...
Article
Introduction: Understanding the recovery in response to different sprint protocols is important for optimizing neuromuscular gains and organizing training sessions in sports. The current study aimed to investigate acute neuromuscular changes following a moderate volume of sprint protocols with and without change-of-direction. Methods: 26 well-trained male collegiate athletes from different sports were randomly allocated into straight-line group (SLG) or change-of-direction group (CODG). The protocols were 1 × 15 repetitions of 20-meter sprints in line (SLG) or with two changes in each repetition (CODG). Knee extension maximal and explosive strength, jump performance, serum creatine kinase, and quadriceps and hamstrings echo intensity were collected pre-, post- 0, 24, 48, and 72 h post-exercise. Results: There were no significant changes in any of the variables at any time point after the exercise protocols in comparison with pre-exercise values (p > 0.05). Conclusions: The present study suggests that sprint training with moderate volume with or without change of direction does not induce neuromuscular or physiological changes during 72 h post-exercise. This information is especially important for sports staff in order to optimize training prescription and frequency.
... To mobilize additional strength reserves and, thereby, to improve the ability of voluntary muscle activation, it could make sense to combine the following regularities and principles of muscle physiology and biomechanics: (1) The principle of starting power (Hochmuth, 1974), (2) the achievement of highest forces through maximal isometric preload (Bührle et al., 1983;Linnamo, 2002;Linnamo et al., 2006), (3) the possibility to achieve supramaximal forces during eccentric action compared to concentric and isometric ones (e.g., Singh and Karpovich, 1966;Crenshaw et al., 1995;Kellis and Baltzopoulos, 1998;Reeves and Narici, 2003;Wirth and Schmidtbleicher, 2004;Shepstone et al., 2005;Meinel and Schnabel, 2007;Coadore et al., 2014), and (4) the proportionality between force and eccentric velocity (Schmidtbleicher et al., 1981;Röthing and Größing, 1990;Shepstone et al., 2005;Carney et al., 2012). Bührle et al. (1983) explored the influence of maximal preload on the MVC as well as the eccentric force outcome using overload. ...
... In fact, it is well known that eccentric muscle action can generate higher forces than the isometric and concentric one (e.g., Singh and Karpovich, 1966;Crenshaw et al., 1995;Kellis and Baltzopoulos, 1998;Reeves and Narici, 2003;Wirth and Schmidtbleicher, 2004;Shepstone et al., 2005;Meinel and Schnabel, 2007;Coadore et al., 2014). ...
Article
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The improvement of power is an objective in training of athletes. In order to detect effective methods of exercise, basic research is required regarding the mechanisms of muscular activity. The purpose of this study is to investigate whether or not a muscular pre-activation prior to an external impulse-like force impact has an effect on the maximal explosive eccentric Adaptive Force (xpAFeccmax). This power capability combines different probable power enhancing mechanisms. To measure the xpAFeccmax an innovative pneumatic device was used. During measuring, the subject tries to hold an isometric position as long as possible. In the moment in which the subjects’ maximal isometric holding strength is exceeded, it merges into eccentric muscle action. This process is very close to motions in sports, where an adaptation of the neuromuscular system is required, e.g., force impacts caused by uneven surfaces during skiing. For investigating the effect of pre-activation on the xpAFeccmax of the quadriceps femoris muscle, n = 20 subjects had to pass three different pre-activation levels in a randomized order (level 1: 0.4 bar, level 2: 0.8 bar, level 3: 1.2 bar). After adjusting the standardized pre-pressure by pushing against the interface, an impulse-like load impacted on the distal tibia of the subject. During this, the xpAFeccmax was detected. The maximal voluntary isometric contraction (MVIC) was also measured. The torque values of the xpAFeccmax were compared with regard to the pre-activation levels. The results show a significant positive relation between the pre-activation of the quadriceps femoris muscle and the xpAFeccmax (male: p = 0.000, η2= 0.683; female: p = 0.000, η2= 0.907). The average percentage increase of torque amounted +28.15 ± 25.4% between MVIC and xpAFeccmax with pre-pressure level 1, +12.09 ± 7.9% for the xpAFeccmax comparing pre-pressure levels 1 vs. 2 and +2.98 ± 4.2% comparing levels 2 and 3. A higher but not maximal muscular activation prior to a fast impacting eccentric load seems to produce an immediate increase of force outcome. Different possible physiological explanatory approaches and the use as a potential training method are discussed.
... Although Rahbek et al. (2014) also confirmed that lengthening actions elicits greater acute anabolic intracellular signaling than shortening contractions, it was found that these two modes of muscle contraction lead to similar muscle mass accretion after resistance training. This data was corroborated by Cadore et al. (2014), Farup et al. (2014), and Moore, Young, & Phillips (2012). ...
... The authors equalized the total work of lengthening and shortening contractions by allowing the execution of a higher number of concentric repetitions, which probably equaled the anabolic stimulation of these two types of contraction and caused the same muscle hypertrophy. In contrast, the outcomes recorded by Cadore et al. (2014), Farup et al. (2014), and Rahbek et al. (2014) were unexpected. They reported similar muscle mass accretion between eccentric and concentric contractions even when the total work was not equalized. ...
Article
Studies from the 20th century had proposed that exercise-derived anabolism is the result of acute release of anabolic hormones. Recent advances in molecular biology have validated the hormonal theory, but have raised the question of whether exercise-induced anabolic hormones are related to chronic hypertrophy. Intrinsic factors of muscle contraction, on the other hand, seem to play an important role in exercise-induced protein synthesis and hypertrophy. This review seeks to highlight the role of anabolic pathways related to resistance exercise and express its applicability in resistance training considering the following variables: (a) intensity; (b) volume; (c) rest interval; (d) types of contraction; (e) velocity of contraction; (f) exercise order; and (g) frequency. We conclude that resistance training-induced hypertrophy is likely explained by intrinsic factors rather than by the hormonal theory. Regarding the following training recommendations, multiple sets, long rest intervals, dynamic and high-velocity contractions and prioritizing the exercise order are most likely to produce the greatest enhancement in skeletal muscle hypertrophy. Training intensity may vary, as low (30% one-repetition maximum [1RM]) or high (80% 1RM) intensities induce similar improvements in hypertrophy when performed to a maximal level of effort. Likewise, training frequency may vary according to individual needs, as the total volume performed within a training week appears to be more strongly related to hypertrophy than the number of weekly training sessions. This review contributes to the development of sports performance, aesthetics, and quality of life, and to the prevention or treatment of muscle loss caused by aging or illness.
... It is often assumed that eccentric (ECC) contractions can induce greater hypertrophy than concentric (CON) contractions because they generate greater muscle force, neuromuscular adaptations, IGF-1 mRNA expression, activation and proliferation of satellite cells, and a more rapid rise in protein synthesis (16,20,28,37). However, some authors (8,9,20,39,45) have suggested that there are no differences in strength and hypertrophy gains between ECC and CON resistance training, particularly if the exercises are performed at the same intensity or work volume. Thus, the differential impact of ECC or CON on strength and hypertrophy gains is still a debatable issue, while the mechanisms regulating these adaptations have not yet been fully elucidated. ...
... In our study, the time under tension of the slow-velocity training groups (SE and SC) was 4 times longer than the others (;40 vs. ;10 seconds). Although some studies have argued that strength training with eccentric and concentric contractions leads to similar hypertrophy (6,8,9), a few studies have still indicated that concentric training is the more effective method (29,37). Conversely, Higbie et al. (23) reported that increases in muscle hypertrophy are slightly greater after 10 weeks of eccentric training than with concentric training. ...
Article
Ünlü, G, Çevikol, C, and Melekoğlu, T. Comparison of the effects of eccentric, concentric, and eccentric-concentric isotonic resistance training at two velocities on strength and muscle hypertrophy. J Strength Cond Res XX(X): 000-000, 2019-The aim of this study was to compare the effects of concentric, eccentric, and eccentric-concentric isotonic resistance training at both fast and slow velocities to determine whether contraction modality affects muscle strength and hypertrophy. Forty-one young, healthy males (mean age 21.1 ± 1.8 years; height 178.9 ± 6.1 cm; body mass 70.5 ± 9.8 kg; and body mass index 22.0 ± 2.6 kg·m) were randomly assigned for 12 weeks to 1 of 5 resistance training groups to perform leg extension exercises 3 days a week (fast-eccentric; fast-concentric [FC]; slow-eccentric [SE]; slow-concentric; and concentric-eccentric [CE], 30°·s for slow and 180°·s for fast contractions), or to a nontraining control group (CG). Isotonic strength (1 repetition maximum [1RM]), isokinetic strength (peak torque), and quadriceps femoris muscle volume were measured before and after the 12 weeks of training program. In the early phase of the training period (first 3 weeks), the 1RM values of SE, FC, and CE increased remarkably (19.70, 13.73, and 19.35%, respectively; p < 0.05). Significant increases compared with the CG were found for muscle isotonic strength (∼25-41%, p < 0.001) and isokinetic peak torque at 60°·s (∼13-32%, p < 0.05) in all training groups after the 12 weeks of the training period. No statistically significant interactions between the group and time were found on isokinetic peak torques at 180°·s and muscle volume. Our results, therefore, suggest that all the training modalities in our study have the potential to induce isotonic strength gain in knee extensors, and there is insufficient evidence for the superiority of any specific mode of muscle contraction or velocity.
... This result is different from those of previous studies. Cadore et al. [36] reported a similar increase after 6 weeks of ECT and CCT in the VL MT of twenty-two healthy adults. In the study by Norrbrand et al. [37], 15 healthy adults performed ECT and CCT for 5 weeks and MT increases of the quadriceps in the ECT group was reported, though the increase was not significant. ...
... In addition, metabolic damage of myosin and actin protein and sarcomere degneration cause decrease of muscle mass and MT [39]. It has been reported, however, that ECT increases mus- cle proportions and sizes of type II fibers [36,40,41]. It was also reported that slow-velocity ECT, when performed by those with chronic stroke, increases the binding force between myosin and actin and induces simultaneous contraction of type I and type II muscle fibers [17]. ...
... Effect sizes (Cohen's d) were calculated from previous studies employing similar interventions from mean changes in strength (Kay et al. 2016), hypertrophy (Cadore et al. 2014), andmobility (LaStayo et al. 2003). To ensure adequate statistical power for all analyses, power analysis was conducted for hypertrophy (i.e. the variable with the smallest effect size) using the following parameters (power = 0.80, alpha = 0.05, effect size = 1.58). ...
... However, no significant correlations were observed between the improvements in muscle strength or size and mobility. Possibly of greater interest was that although a small but significant reduction in muscle thickness occurred during the detraining period, no significant reduction in strength occurred, indicative that neuromuscular adaptations (Cadore et al. 2014) were important for both the improvement, and then retention, of strength. Regardless, strength (~ 71-85% of the mean increase maintained) and muscle thickness (~ 62-71% of the mean increase preserved) remained significantly greater than baseline after the 8-week detraining period. ...
Article
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IntroductionEccentric exercise can reverse age-related decreases in muscle strength and mass; however, no data exist describing its effects on postural sway. As the ankle may be more important for postural sway than hip and knee joints, and with older adults prone to periods of inactivity, the effects of two 6-week seated isokinetic eccentric exercise programmes, and an 8-week detraining period, were examined in 27 older adults (67.1 ± 6.0 years).Methods Neuromuscular parameters were measured before and after training and detraining periods with subjects assigned to ECC (twice-weekly eccentric-only hip and knee extensor contractions) or ECCPF (identical training with additional eccentric-only plantarflexor contractions) training programmes.ResultsSignificant (P < 0.05) increases in mobility (decreased timed-up-and-go time [− 7.7 to − 12.0%]), eccentric strength (39.4–58.8%) and vastus lateralis thickness (9.8–9.9%) occurred after both training programmes, with low-to-moderate weekly rate of perceived exertion (3.3–4.5/10) reported. No significant change in any postural sway metric occurred after either training programme. After 8 weeks of detraining, mobility (− 8.2 to − 11.3%), eccentric strength (30.5–50.4%) and vastus lateralis thickness (6.1–7.1%) remained significantly greater than baseline in both groups.Conclusion Despite improvements in functional mobility, muscle strength and size, lower-limb eccentric training targeting hip, knee and ankle extensor muscle groups was not sufficient to influence static balance. Nonetheless, as the beneficial functional and structural adaptations were largely maintained through an 8-week detraining period, these findings have important implications for clinical exercise prescription as the exercise modality, low perceived training intensity, and adaptive profile are well suited to the needs of older adults.
... Studies have shown that isokinetic resistance training at a spectrum of joint angular velocities increases muscle strength [34,35], and rate of force development [34]. In addition, researchers have verified that multiple-joint isokinetic resistance training has direct beneficial carryover effects to dynamic exercise performance in addition to isokinetic strength gains [36], and some researchers have done preliminary research in this area [37][38][39][40][41]. ...
... Studies have shown that isokinetic resistance training at a spectrum of joint angular velocities increases muscle strength [34,35], and rate of force development [34]. In addition, researchers have verified that multiple-joint isokinetic resistance training has direct beneficial carryover effects to dynamic exercise performance in addition to isokinetic strength gains [36], and some researchers have done preliminary research in this area [37][38][39][40][41]. ...
Article
Isokinetic muscle strength training refers to the mode of movement based on constant speed and variable resistance, which can guarantee the maximum resistance and force-distance output of each muscle in different angles of exercise. In this paper, we develop an isokinetic muscle strength training strategy based on adaptive gain and cascade PID controller for ankle rehabilitation on our newly developed ankle robotic system. At first, a heuristic threshold intention recognition method based on time series integrated was proposed to precisely recognize the motion intention, thus inducing the motion in this direction. Then, an adaptive gain algorithm was developed to provide speed gain for the isokinetic training, to avoid jitter during speed switching. At last, the isokinetic characteristic was realized by cascade PID controller, which can control the motion velocity in a given range with fast response speed. Experiments with healthy subjects showed good performance in the smoothness of the control system, the accuracy, and the real-time performance of velocity tracking. By introducing the isokinetic characteristic in ankle rehabilitation, the ankle robot can provide resistance training at a constant speed no matter how much force the patient uses, which is a very functional supplement and improvement for ankle rehabilitation.
... Interestingly, the authors reported no such association for muscle cross-sectional area (CSA), suggesting that EI may provide information that is not redundant with measures of muscle size (Mota et al. 2018). Perhaps even more valuable than correlationbased studies are data demonstrating significant reductions in EI following exercise interventions in older adults (Cadore et al. 2014;Radaelli et al. 2014). Recently, Radaelli et al. (2019) demonstrated that 12 weeks of lower-extremity muscle power training resulted in significant reductions in EI for the quadriceps femoris. ...
Article
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Ultrasonography-derived cross-sectional area (CSA) and echo intensity (EI) are increasingly utilized by investigators to study muscle size and quality, respectively. We sought to examine age, sex, and region (proximal, middle, distal) differences in vastus lateralis and rectus femoris CSA and EI, and determine whether correction for subcutaneous fat thickness influences the magnitude of EI differences. Fifteen younger men (mean age=23 years), fifteen younger women (21 years), eleven older men (74 years), and fifteen older women (70 years) participated. Clear differences were observed among age, sex, and region for vastus lateralis CSA (p≤0.013, d=0.38-0.73), whereas rectus femoris CSA was only different between younger and older participants at the proximal region (p=0.017, d=0.65). Uncorrected EI was greatest at the distal region of both muscles (p<0.001, d=0.59-1.38), with only the younger men having significantly lower EI values than the other groups (p≤0.043, d=0.37-0.63). Subcutaneous fat correction resulted in a marked increase in the magnitude of sex-specific EI differences (p≤0.032, d≥0.42). Additionally, subcutaneous fat correction increased the uniformity of EI throughout the thigh. These findings highlight considerable region-specific differences in muscle size and quality among younger and older men and women, and highlight the need to correct for subcutaneous fat thickness when examining EI. Novelty Bullets  Rectus femoris CSA is similar between younger and older adults except at the most proximal site evaluated.  Age-and sex-specific differences in uncorrected EI are non-uniform across the thigh.  Correction for subcutaneous fat thickness substantially increased EI in women, resulting in greater sex differences.
... However, it is known that strength development may result from neural activation of muscle as well as hypertrophy (6,13). Furthermore, the short or long term effects of eccentric and concentric resistance training on inducing gains in neural activation is still a debatable issue, with some studies reporting greater neural activation of muscle with eccentric, some with concentric and some with similar within both training modes (5). In a similar vein, enhanced strength caused by neural adaptations after eccentric or concentric resistance ...
... Several training interventions with isometric (Alegre et al., 2014;Noorkõiv et al., 2015), concentric (Blazevich et al., 2007;Moore et al., 2012), eccentric contractions (Paddon-Jones et al., 2001;Shepstone et al., 2005;Moore et al., 2012), or a combination of the three contraction forms (Alegre et al., 2006;Matta et al., 2015) were able to elicit changes in both muscle strength and size (Higbie et al., 1996;Farthing and Chilibeck, 2003;Vikne et al., 2006;Blazevich et al., 2007). When comparing different forms of muscle contractions, eccentric loading was often (Seger et al., 1998;Farthing and Chilibeck, 2003;Vikne et al., 2006;Maeo et al., 2018), but not always (Higbie et al., 1996;Blazevich et al., 2007;Reeves et al., 2009;Cadore et al., 2014), found to be superior in strength improvement and increase in size when compared to training with concentric or isometric muscle loading. This superior effect is often attributed to the higher force that can be generated during eccentric contractions (Westing et al., 1988;Adams et al., 2004) due to the forcevelocity relationship (Katz, 1939), resulting in a stronger loading stimulus compared to the other two contraction types. ...
Article
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Eccentric loading is an effective stimulus for muscle hypertrophy and strength gains, however, the effect of lengthening velocity is under debate. The purpose of the current study was to investigate the influence of muscle lengthening velocity during eccentric training on muscle hypertrophy and strength gains at a given overall loading volume. Forty-seven participants were randomly assigned to a control (n = 14, age: 26.9 ± 4.1 years) and an experimental group (n = 33, age: 27.1 ± 4.4 years). Each leg of the participants in the experimental group was randomly assigned to one of the four eccentric training protocols with different angular velocities (i.e., 45, 120, 210, and 300°/s). Both the magnitude of loading (100% of the isometric maximum) and overall time under tension was matched between the protocols. The training was performed for 33 sessions, 3 times per week with 5 training sets per session. Before and after the intervention, the maximum isometric knee extension moments were measured in all groups using dynamometry, vastus lateralis (VL) muscle anatomical cross-sectional area, and VL muscle volume were measured in the experimental group using magnetic resonance imaging. Data was analyzed in a mixed-design analysis of variance. After the training intervention, the maximum knee joint moments increased in the experimental group (14.2%, p < 0.05) but not the control group. VL anatomical cross-sectional area and VL muscle volume increased significantly (p < 0.05) in the experimental group (5.1 and 5.7%, respectively), but we did not find any significant differences between the four training protocols in all investigated parameters (p > 0.05). The present study provides evidence that muscle hypertrophy and strength gains after eccentric exercise is velocity-independent when load magnitude and overall time under tension are matched between conditions. This is likely due to the similar mechanical demand for the muscle induced by the loading conditions of all four training protocols. The better control of motion and the potentially decreased joint loading compared to high lengthening velocity contractions support the application of slow eccentric exercises in special populations like elderly and people with neurological and musculoskeletal diseases.
... However, adaptations to strength training are also specific to the muscle contraction mode [9,25] and movement pattern [26,27] adopted during training. With respect to contraction mode, the limited evidence to date indicates a lack of differential effect of concentric vs. eccentric training on RFD [28,29], although further study is warranted. However, the movement pattern specificity of RFD enhancements has not been explicitly examined despite maximum muscle strength changes being highly specific to the movement pattern of the training exercise [26,27]. ...
Article
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Background Muscular rate of force development (RFD) is positively influenced by resistance training. However, the effects of movement patterns and velocities of training exercises are unknown. Objectives To determine the effects of velocity, the intent for fast force production, and movement pattern of training exercises on the improvement in isometric RFD from chronic resistance training. Methods A systematic search of electronic databases was conducted to 18 September, 2018. Meta-regression and meta-analytic methods were used to compute standardized mean differences (SMD ± 95% confidence intervals) to examine effects of movement pattern similarity (between training and test exercises; specific vs. non-specific) and movement speed (fast vs. slow vs. slow with intent for fast force production) for RFD calculated within different time intervals. Results The search yielded 1443 articles, of which 54 met the inclusion criteria (59 intervention groups). Resistance training increased RFD measured to both early (e.g., 50 ms; standardized mean difference [95% CI] 0.58 [0.40, 0.75]) and later (e.g., 200 ms; 0.39 [0.25, 0.52]) times from contraction onset, as well as maximum RFD (RFDmax; 0.35 [0.21, 0.48]). However, sufficient data for sub-analyses were only available for RFDmax. Significant increases relative to control groups were observed after training with high-speed (0.54 [0.05, 1.03]), slow-speed with intent for fast force production (0.41 [0.20, 0.63), and movement pattern-specific (0.38 [0.17, 0.59]) exercises only. No clear effect was observed for slow-speed without intent for fast force production (0.21 [0.00, 0.42], p = 0.05) or non-movement-specific (0.27 [− 0.32, 0.85], p = 0.37) exercises. Meta-regression did not reveal a significant difference between sexes (p = 0.09); however, a negative trend was found in women (− 0.57 [− 1.51, 0.37], p = 0.23), while a favorable effect was found in men (0.40 [0.22, 0.58], p < 0.001). Study duration did not statistically influence the meta-analytic results, although the greatest RFD increases tended to occur within the first weeks of the commencement of training. Conclusions Resistance training can evoke significant increases in RFD. For maximum (peak) RFD, the use of faster movement speeds, the intention to produce rapid force irrespective of actual movement speed, and similarity between training and testing movement patterns evoke the greatest improvements. In contrast to expectation, current evidence indicates a between-sex difference in response to training; however, a lack of data in women prevents robust analysis, and this should be a target of future research. Of interest from a training program design perspective was that RFD improvements were greatest within the first weeks of training, with less ongoing improvement (or a reduction in RFD) with longer training, particularly when training velocity was slow or there was a lack of intent for fast force production.
... Thus, endurance training, resistance training or both have the potential to improve muscle EI. Concurrent training, hydraulic-resistance machine training, weight-bearing resistance training and walking can reportedly improve muscle EI (Cadore et al. 2014;Radaelli et al. 2014;Yoshiko et al. 2017). ...
Article
This study was performed to identify factors that discriminate muscle echo intensity (EI) among parameters of body composition, physical function and daily physical activity in elderly individuals. A total of 209 men and women (73.7 ± 2.8 y) were evaluated. EI was measured on ultrasonographic axial thigh muscle images. The participants were categorized into the low, mid and high EI groups. We measured the skeletal muscle mass index (SMI) and physical functions. The high EI group exhibited a significantly lower SMI, slower 5-m walking time and shorter 6-min walking distance than the low EI group and had a shorter moderate-intensity activity time than the mid EI group. As a result of the discriminant analysis, elderly individuals were categorized into EI groups by SMI, daily activity and physical function. The data indicate that morphologic and functional parameters and the daily activity level help to discriminate higher and lower muscle EI.
... I sokinetic dynamometry is widely regarded as the gold standard in muscle testing (22); it is also considered a highly effective means for rehabilitation and conditioning of muscle function (7,16,38). Launched in the late 60s, angular isokinetic dynamometers (AIDs) were designed to measure the muscular moment output and its related mechanical parameters such as angular work and power mainly during concentric conditions, and where relevant, under isometric exertions. The introduction, in the mid-80s, of electrical motors as the power source (sometimes through a hydraulic system) enabled measurement of eccentric muscular action, thus allowing for a comprehensive mapping of the muscle's mechanical potential. ...
Article
Dvir, Z and Müller, S. Multiple-joint isokinetic dynamometry: a critical review. J Strength Cond Res XX(X): 000-000, 2018-Angular isokinetic dynamometry (AID) is widely regarded as the gold standard for dynamic muscle performance testing. Based on the rotational movement of its actuator, AID targets "single-joint" (knee, shoulder, hip, etc.) configurations namely measurement of muscle potential while it moves the lever arm-limb assembly ostensibly around a single fixed axis. On the other hand, the application of multiple-joint isokinetic dynamometry (MID) is relatively narrow, both in research and in practice. This situation is due, possibly, to the fact that these dynamometers are generally more limited in scope namely to testing/conditioning of combined hip, knee, ankle motion (leg press), combined shoulder, elbow motion, and lifting motion patterns, despite the fact that all 3 are associated with higher functionality. However, with the emerging importance of MID, this critical review takes a fresh look at its various aspects including the terminology and classification of multiple-joint isokinetic dynamometers; the problem of scaling namely the need to adjust the range of motion and linear velocities to subjective anthropometric measures; specific technical and methodological issues that underlie the valid application of these dynamometers; available reference values; and the reproducibility of MID-based test findings. Analysis of these topics indicates that MID may validly and effectively be applied for the assessment and conditioning of specific muscle action patterns. However, there is a clear need for standardization of tests and for conditioning protocols alongside research into the use of this method in various clinical cohorts.
... In the literature, plyometric training is also known as stretch-shortening cycle exercise training (Faigenbaum, 2011;Ryoichi et al., 2016;Guex et al., 2016). In fact, this involves a short series of extremely rapid and strong successive muscle contractions (with more or fewer repeats), all of them eccentric, performed as single executions or series (cycles) of executions, ending with an equally rapid and strong concentric muscle contraction (Bullimore et al., 2007;Kosterina et al., 2008;McDaniel et al., 2010;Cadore et al., 2014;Franchi et al., 2017). ...
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Plyometric training is a training method dedicated specifically to high performance athletes, involving a general effort of psycho-physical commitment, with explosive movements being executed or repeated at very short time intervals. The main goal of plyometric training, through its systematic organization, is the induction, over time, of structural and functional changes in the muscle groups of interest, with optimizing influences on individual sports performance, especially from a topokinetic perspective. The primary requirement in plyometric training is that the time parameter between two consecutive executions must be permanently measured and controlled by the coach, with an aim for the involved duration defined as the latency time to achieve an ideal of zero seconds. The defining feature of this training, given by an extremely short temporal relation between an overcoming movement phase (e.g. upward jump, push, extension) and a yielding movement phase (e.g. damping, flexion), implies that the duration of the two phases is of the order of fractions (tenths or hundredths) of a second. The ideal minimal pursued time is "zero" seconds, the muscle contractions in the two phases usually having the same direction but opposite senses. Plyometric training does not specifically require the development of muscle mass or volume (muscle hypertrophy), but the development of an extremely powerful and rapid explosive force, generated through the contribution of a minimum body muscle mass and maximum physical and mental commitment from an athlete. Rezumat Antrenamentul pliometric este o modalitate de pregătire sportivă, dedicată în mod special sportivilor de performanță consacrați, desfășurată cu un efort general de mare angajament psiho-fizic, mișcările explozive fiind executate sau repetate la intervale foarte scurte de timp. Scopul principal al antrenamentului pliometric, prin organizarea lui sistematică, este pro-ducerea, în timp, a unor modificări structurale și funcționale la nivelul grupelor musculare interesate, cu influențe optimizante asupra performanței sportive individuale, mai ales din perspectivă topocinetică. Cerința primordială în antrenamentul pliometric este aceea că parametrul durată dintre două execuții trebuie măsurat și con-trolat în permanență de antrenor, durata respectivă, definită ca timp de latență, trebuind să tindă spre un ideal de zero secunde. Caracteristica definitorie a acestui antrenament, dată de un raport temporal extrem de scurt dintre o fază a mișcării de tip învingere (ex. desprindere, împingere, extensie) și una de tip cedare (ex. amortizare, flexie), presupune ca durata dintre cele două faze să fie la nivel de fracțiuni de secundă (zecimi sau sutimi). Idealul temporal minim urmărit este "zero" secunde, contracțiile musculare din cele două faze având, de obicei, aceeași direcție, dar sensuri opuse. Antrenamentul pliometric nu urmărește, în mod expres, dezvoltarea masei sau a volumului muscular (hipertrofia musculară), ci dezvoltarea unei forțe explozive, extrem de puternice și rapide, realizată prin contribuția unui minimum de masă musculară corporală și a unui maximum de angrenare fizică și psihică, din partea unui sportiv. Cuvinte cheie: antrenament pliometric; mărimi vectoriale; sinergism muscular; lucru excentric.
... Because published studies often discuss their results while comparing the values found with those available in the literature, 10,16 it is important to identify the influence of using different US systems when determining the muscle's EI. Therefore, the aim of the present study was to verify the reliability and the agreement of rectus femoris (RF) muscle EI values calculated from images of a similar muscle location, using two different US systems. ...
Article
Objective Echo intensity measurements are highly influenced by ultrasound system and parameters used for measurement, making comparisons of results obtained from different ultrasound machines difficult. Therefore, it is necessary to understand how reliability changes when using different ultrasound systems and parameters. Materials and Methods ALOKA SSD4000 and GE LOGIQ P6 systems were used to compare rectus femoris echo intensity in 16 healthy young subjects (eight women) using different depths (D), gains (G), and frequencies (F). The following settings were adopted: ALOKA 1 (D6/G30/F7.5), ALOKA 2 (D6/G45/F7.5), ALOKA 3 (D6/G30/F10), LOGIQ 1 (D6/G50/F15), LOGIQ 2 (D6/G0/F15), LOGIQ 3 (D6/G0/F10), and LOGIQ 4 (D6/G30/F10). Intraclass correlation coefficient, standard error of the measure, minimum difference, and Bland-Altman tests were performed to calculate reliability and agreement between systems’ settings. Results ALOKA 1 × LOGIQ 1 , ALOKA 1 × LOGIQ 4 , and ALOKA 3 × LOGIQ 1 showed moderate to high ICCs and agreement on the Bland-Altman test. Conclusion Echo intensity varies between systems and parameters, but reliability can be increased by adjusting the ultrasound settings.
... To date, the effect of the training methods on improving the performance is well documented; yet, there is little information on how the concentric or eccentric exercises and NMES affect the muscle's passive viscoelastic properties. [19][20][21] Understanding the adaptations in mechanical properties of the muscles as a result of different training methods may allow appropriate exercise prescription and guide the management of hamstring injuries. Therefore, examining the effect of training methods on muscle viscoelastic properties may be critical for identifying the decisive factor for rehabilitation and training. ...
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This study investigated the effects of hamstring training methods on the passive viscoelastic properties of hamstring and quadriceps muscles and the relationship of these properties to lower extremity power, hamstring flexibility, and agility. A total of forty healthy individuals were recruited for this study. Participants performed Nordic hamstring exercises (n = 14), hamstring curl exercises (n = 14), or received neuromuscular electrical stimulation (NMES; n = 13) for eight weeks. Measurements were taken both before and one week after the interventions of the viscoelastic properties of hamstring and quadriceps muscles, strength, flexibility, agility, and lower extremity power. Nordic hamstring exercises increased hamstring muscle elasticity while decreasing quadriceps and hamstring muscle stiffness; whereas leg curl exercises increased quadriceps and hamstring muscle stiffness while decreasing quadriceps muscle tone (p < 0.05). Both strengthening methods increased agility, hamstring flexibility, and vertical jump. NMES produced no noticeable effects. Eccentric and concentric training methods had inverse effects on both hamstring and quadriceps muscles’ viscoelastic parameters, but had similar improvements on performance parameters. Since changes in viscoelastic parameters of muscle could affect musculotendinous systems’ compliance, clinicians should consider viscoelastic properties over performance parameters, when prescribing concentric or eccentric exercises.
... The rate of the gradual increase in load was dependent on the participant's self-perceived capacity and readjusted for the next series using Lombardi [37] calculations. Performance time for each contraction (concentric and eccentric) was 1.5 s controlled by an electronic metronome (Quartz, CA, USA) [38]. After the performance of 1RM test, the load corresponding to 60% of 1RM of each individual was fixed. ...
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Background: In the literature, professions that impose body standards for daily performance are designated as non-conventional professions (i.e. models, athletes, ballet dancers), with great emphasis on the female population. More than a job, it becomes a lifestyle to those inserted in this environment, thus, thousands of children and adolescents seek the inclusion and success in these professions due to financial and media gains. Such professions are associated to several health-related risk factors. The purpose of this study was to identify whether there is a relationship between physical fitness levels, cardiometabolic health markers, mental health and dietary habits in non-conventional professions. Methods: The sample consisted of 41 female individuals aged between 14 and 24 years, divided in four groups, control group/ university students (UG=11), models (MG=11), ballet dancers (BG=11), and athletes group (AG=8). Physical fitness outcomes (cardiorespiratory fitness, flexibility, maximal dynamic strength, muscular endurance and body composition); biochemical outcomes (high density lipoprotein [HDL], low density lipoprotein [LDL], total cholesterol [TC], fasting glucose [FG], fasting insulin [FI], C-reactive protein [CRP]), diet quality and mental health were evaluated. Results: No impairments were observed in the health markers evaluated, both for health-related physical fitness and biochemical outcomes. Even with statistically significant differences between the groups for chronological age (p=0.002), menarche (p=0.004), career length (p=0.001), height (p=0.001), body mass index (p=0.018), waist-to-height ratio (p<0.001), %Fat (p=0.020), VO2peak (p=0.020), maximal dynamic strength of knee extensors (p=0.031) and elbow flexors (p=0,001) and flexibility (p<0.001), all these values are within the normal range for health. Conclusion: The professions analyzed do not seem to interfere in the physical and metabolic health of the girls assessed. However, regarding mental health, the evaluated age group was susceptible to depressive symptoms.
... decreased intramuscular fat and connective tissue, decreased EI) and hypertrophy (i.e. increased MT) (6,46,47), it is possible that the inverse relationship between MT and EI may have been facilitated by training-induced adaptations. Nevertheless, we report that the difference in EI between the deep and superficial portions of the VL (EI DIFF ) is amplified with increasing MT, demonstrating that thicker muscles have greater disparities in EI between the deep and superficial portions, despite having lower EI values overall. ...
Article
Background: Ultrasonography is used to evaluate muscle quality (i.e. echo intensity [EI]), but an attenuation of ultrasound waves occurs in deeper tissues, potentially affecting these measures. Purpose: To determine whether muscle thickness (MT) affects EI and if EI varies between the superficial and deep portions of the muscle. Materials and methods: MT, EI, subcutaneous adipose tissue thickness (SAT), tissue depth (DISDEEP), and EI of the overall (EIFULL) as well as deep (EIDEEP) and superficial (EISUPF) portions of the vastus lateralis (VL) were assessed in 33 resistance-trained males using ultrasonography. The difference (EIDIFF) between EISUPF and EIDEEP was calculated. Mean differences between EIFULL, EISUPF, and EIDEEP were analyzed using a repeated-measures analysis of variance (ANOVA). Relationships between measures of muscle depth/ thickness and EI were examined using Pearson's r. Results: EISUPF was greater than EIDEEP (P < 0.001) and EIFULL (P < 0.001). MT was negatively correlated with EIFULL (P < 0.001) and positively correlated with EIDIFF (P < 0.001). SAT was not correlated with any EI measure, but DISDEEP was positively correlated with EIDIFF (P < 0.001). Conclusion: EI of the VL is heterogeneous, as the deeper portion produces lower values than the superficial portion. Thicker muscles present lower EI but have greater discrepancies in EI between the superficial and deep portions. Although SAT was not correlated with EI, DISDEEP was related to EIDIFF, demonstrating that the combination of MT and SAT should be considered when evaluating muscle quality. Future research is necessary to determine if changes in EI following resistance training are driven by increases in MT.
... The rate of the gradual increase in load was dependent on the participant's self-perceived capacity and readjusted for the next series using Lombardi [37] calculations. Performance time for each contraction (concentric and eccentric) was 1.5 s controlled by an electronic metronome (Quartz, CA, USA) [38]. After the performance of 1RM test, the load corresponding to 60% of 1RM of each individual was fixed. ...
Article
Full-text available
Background: In the literature, professions that impose body standards for daily performance are designated as non-conventional professions (i.e. models, athletes, ballet dancers), with great emphasis on the female population. More than a job, it becomes a lifestyle to those inserted in this environment, thus, thousands of children and adolescents seek inclusion and success in these professions due to financial and media gains. Such professions are associated with several health-related risk factors. The purpose of this study was to identify and compare among physical fitness levels, cardiometabolic health markers, mental health and dietary habits in non-conventional professions. Methods: The sample consisted of 41 female individuals aged between 14 and 24 years, allocated into four groups, control group composed by university students (UG = 11), models (MG = 11), ballet dancers (BG = 11), and athletes' group (AG = 8). Physical fitness outcomes (cardiorespiratory fitness, flexibility, maximal dynamic strength, muscular endurance and body composition); biochemical outcomes (high-density lipoprotein [HDL], low-density lipoprotein [LDL], total cholesterol [TC], fasting glucose [FG], fasting insulin [FI], C-reactive protein [CRP]), diet quality and mental health were evaluated. Results: No impairments were observed in the health markers evaluated among groups, both for health-related physical fitness and biochemical outcomes. However, low levels of bone mineral density (BMD) were observed. Even with statistically significant differences between the groups for chronological age (p = 0.002), menarche (p = 0.004), career length (p = 0.001), height (p = 0.001), body mass index (p = 0.018), waist-to-height ratio (p < 0.001), %Fat (p = 0.020), VO2peak (p = 0.020), maximal dynamic strength of knee extensors (p = 0.031) and elbow flexors (p = 0,001) and flexibility (p < 0.001), all these values are within the normal range for health. Conclusion: The professions analyzed do not seem to interfere in the physical fitness and cardiometabolic health of the girls assessed. However, we identified that exposure to these profession can impair mental health (depressive symptoms in 100% of participants) and body composition (BMD 63% of participants).
... However, chronic concentric and eccentric exercise protocols do not lead to sarcomerogenesis in mouse skeletal muscle (Morais et al. 2020). Nevertheless, some studies (Blazevich et al. 2007;Cadore et al. 2014;Schoenfeld et al. 2017) have indicated the same increases in strength and muscle hypertrophy after eccentric and concentric contraction, specifically in similar intensity or volume of exercises. On the other hand, excessive eccentric exercise inhibits hypertrophy (Da Rocha et al. 2016), endoplasmic reticulum stress (Pereira et al. 2016a, b), and impairs the insulin signal transduction (Pereira et al. 2016a, b) in mice skeletal muscle. ...
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Skeletal muscle contractions are caused to release myokines by muscle fiber. This study investigated the myogenic regulatory factors, as MHC I, IIA, IIX, Myo-D, MRF4, Murf, Atrogin-1, Decorin, Myonection, and IL-15 mRNA expression in the response of eccentric vs concentric contraction. Eighteen healthy men were randomly divided into two eccentric and concentric groups, each of 9 persons. Isokinetic contraction protocols included maximal single-leg eccentric or concentric knee extension tasks at 60°/s with the dominant leg. Contractions consisted of a maximum of 12 sets of 10 reps, and the rest time between each set was 30 s. The baseline biopsy was performed 4 weeks before the study, and post-test biopsies were taken immediately after exercise protocols from the vastus lateralis muscle. The gene expression levels were evaluated using Real-Time PCR methods. The eccentric group showed a significantly lower RPE score than the concentric group (P ≤ 0.05). A significant difference in MyoD, MRF4, Myonection, and Decorin mRNA, were observed following eccentric or concentric contractions (P ≤ 0.05). The MHC I, MHC IIA, IL-15 mRNA has been changed significantly compared to the pre-exercise in the concentric group (P ≤ 0.05). While only MHC IIX and Atrogin-1 mRNA changed significantly in the eccentric group (P ≤ 0.05). Additionally, the results showed a significant difference in MyoD, MRF4, IL-15, and Decorin at the follow-up values between eccentric or concentric groups (P ≤ 0.05). Our findings highlight the growing importance of elucidating the different responses of muscle growth factors associated with a myogenic activity such as MHC IIA, Decorin, IL-15, Myonectin, Decorin, MuRF1, and MHC IIX mRNA in following various types of exercise.
... Elbow flexor ACSA increased by 11% after 12 weeks (Vikne et al., 2006) and biceps brachii muscle CSA by 6.5% after 9 weeks of ET (Moore et al., 2012). Increases in muscle thickness were also reported for different muscles (Farthing and Chilibeck, 2003;Duclay et al., 2009;Baroni et al., 2013;Guilhem et al., 2013;Cadore et al., 2014;Franke et al., 2014;Leong et al., 2014;Kim et al., 2015;Timmins et al., 2016;Alonso-Fernandez et al., 2018). Interestingly, the comparison of the effects of ET performed with submaximal and supramaximal intensity (80 and 110% of the concentric 1RM, respectively) showed no different effect on biceps brachii thickness (Krentz et al., 2017). ...
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Treatment strategies and training regimens, which induce longitudinal muscle growth and increase the muscles’ length range of active force exertion, are important to improve muscle function and to reduce muscle strain injuries in clinical populations and in athletes with limited muscle extensibility. Animal studies have shown several specific loading strategies resulting in longitudinal muscle fiber growth by addition of sarcomeres in series. Currently, such strategies are also applied to humans in order to induce similar adaptations. However, there is no clear scientific evidence that specific strategies result in longitudinal growth of human muscles. Therefore, the question remains what triggers longitudinal muscle growth in humans. The aim of this review was to identify strategies that induce longitudinal human muscle growth. For this purpose, literature was reviewed and summarized with regard to the following topics: (1) Key determinants of typical muscle length and the length range of active force exertion; (2) Information on typical muscle growth and the effects of mechanical loading on growth and adaptation of muscle and tendinous tissues in healthy animals and humans; (3) The current knowledge and research gaps on the regulation of longitudinal muscle growth; and (4) Potential strategies to induce longitudinal muscle growth. The following potential strategies and important aspects that may positively affect longitudinal muscle growth were deduced: (1) Muscle length at which the loading is performed seems to be decisive, i.e., greater elongations after active or passive mechanical loading at long muscle length are expected; (2) Concentric, isometric and eccentric exercises may induce longitudinal muscle growth by stimulating different muscular adaptations (i.e., increases in fiber cross-sectional area and/or fiber length). Mechanical loading intensity also plays an important role. All three training strategies may increase tendon stiffness, but whether and how these changes may influence muscle growth remains to be elucidated. (3) The approach to combine stretching with activation seems promising (e.g., static stretching and electrical stimulation, loaded inter-set stretching) and warrants further research. Finally, our work shows the need for detailed investigation of the mechanisms of growth of pennate muscles, as those may longitudinally grow by both trophy and addition of sarcomeres in series.
... A randomized parallel trial was designed to compare changes over time in anthropometric estimations of muscle size, strength, and functional ability between three different RT groups (i.e., following a 10-week whole-body RT program using machines only (M), free weights only (FW), or changing halfway (i.e., after 5 weeks) from using M to FW (COMB)) in male adults being novice in RT. A 10-week RT program should be sufficiently long to induce hypertrophic effects on top of initial neurological adaptations (i.e., greater fiber recruitment, rate of discharge, intermuscular coordination), both resulting in strength increases [19,20]. In the present study design we only implemented a COMB group switching from M to FW, and not vice versa, as it is common in novice RT practitioners to start with relatively easy M exercises and later on switch to the more technical FW exercises [5]. ...
Article
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This study compared the effect of a resistance training (RT) program with machines, free weights, or a combination of both on changes in anthropometrics, strength, and functional ability in novice adult males. Thirty-six male novices in RT (18–45 years) followed a 10-week RT program. Participants were randomly assigned to one of three groups (N = 12 each): machines only; free weights only; or switching from machines to free weights (after 5 weeks). Muscle size (circumferences of upper arm, thigh and chest), strength (1 Repetition Maximum) on both machines and free weights, and functional ability (Functional Movement ScreenTM (Functional Movement Systems Inc., Chatham, VA, USA)) were assessed prior to the RT program, halfway at 5 weeks, and within one week after the final training bout. Repeated measures MANOVAs showed no significant time by RT group interactions for the different outcome measures. Regardless of RT group, significant improvements over time were observed for anthropometrics (F = 9.144, p < 0.001), strength (F = 6.918, p < 0.001), and functional ability (F = 25.578, p < 0.001). To conclude, similar gains in muscularity, strength, and functional ability can be expected for male novices in RT regardless of the equipment being used and without a fallback when changing from machines to free weights. Accordingly, any choice of RT equipment can be made, considering individual preferences.
... Given that published research provides support that highintensity RET improves muscle strength, mass, and composition in young individuals, proxy measures of MQ assessed with imaging techniques such as EI measured via US would also be expected to demonstrate this MQ improvement. However, a majority of the research demonstrating that exercise interventions increase MQ as reflected by a decrease in muscle EI have been conducted in older adults or diseased populations (Radaelli et al., 2013Cadore et al., 2014;Wilhelm et al., 2014;Yoshiko et al., 2017Yoshiko et al., , 2018Yamada et al., 2019). Few investigations have examined the impact of RET on EI in young individuals, making it difficult to make definitive conclusions. ...
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Muscle quality (MQ), defined as the amount of strength and/or power per unit of muscle mass, is a novel index of functional capacity that is increasingly relied upon as a critical biomarker of muscle health in low functioning aging and pathophysiological adult populations. Understanding the phenotypical attributes of MQ and how to use it as an assessment tool to explore the efficacy of resistance exercise training interventions that prioritize functional enhancement over increases in muscle size may have implications for populations beyond compromised adults, including healthy young adults who routinely perform physically demanding tasks for competitive or occupational purposes. However, MQ has received far less attention in healthy young populations than it has in compromised adults. Researchers and practitioners continue to rely upon static measures of lean mass or isolated measures of strength and power, rather than using MQ, to assess integrated functional responses to resistance exercise training and physical stress. Therefore, this review will critically examine MQ and the evidence base to establish this metric as a practical and important biomarker for functional capacity and performance in healthy, young populations. Interventions that enhance MQ, such as high-intensity stretch shortening contraction resistance exercise training, will be highlighted. Finally, we will explore the potential to leverage MQ as a practical assessment tool to evaluate function and enhance performance in young populations in non-traditional research settings.
... The participants were randomly divided into 3 groups: control group (CG) made up of 13 subjects, who did not carry out the intervention program; experimental group 1 (EG1) formed by 13 subjects (2 were lost during the follow-up of the study), who carried out the intervention program for 6 weeks, performing the eccentric repetition of the SLDSe during 6 s; and experimental group 2 (EG2) formed by 13 subjects (1 was lost during the follow-up of the study), who carried out the same eccentric training program as EG1 but eccentric repetition of the SLDSe during 3 s (Figure 1). The sample size was calculated beforehand based on previous research [19], which measured the influence of a 6-week eccentric training program on VL thickness. The minimal number of subjects required to attain a power of 0.9 and a bilateral alpha level of 0.05 was calculated to be 8 participants per group. ...
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The purpose was to examine the effect of 6-week eccentric single-leg decline squat (SLDSe) training with two technical execution times (3 s or 6 s) on changes related to the structural properties of the vastus lateralis (VL) and patellar tendon (PT). Thirty-six physical active volunteers were randomly divided into three groups: control group (CG, n = 13, age = 20.8 ± 1.9 years, no intervention program), experimental group 1 (EG1, n = 11, age = 21.6 ± 2.5 years, execution time = 6 s) and experimental group 2 (EG2, n = 12, 21.1 ± 1.2 years, execution time = 3 s). Participants completed a 6-week SLDSe training program (80% of 1-RM) three days a week. The structural characteristics of the VL and the PT were measured with ultrasonography before and after 6-week SLDSe training and after 6 weeks of de-training. Our results indicate that EG1 increased ≈21.8% the thickness of the PT and EG2 increased ≈15.7% the thickness of the VL after the 6-week intervention program. EG1 and EG2 showed greater values (p < 0.05) of lean mass and lower values (p < 0.05) of fat percentage on the thigh after the intervention program. In conclusion, the SLDSe training carried out with the execution time of 6 s had greater effects on the structural and elastic properties of the PT, and the exercise with the execution time of 3 s caused greater structural adaptations in the VL musculature.
... performance, aging effects on muscle quality, and effects of resistance training on skeletal muscle (5,12,16). In fact, previous studies have reported differences in echo intensity with aging (15,34) and decreases in echo intensity after resistance training protocols in young and older adults (35,36). However, these findings are not consistent throughout the literature and often lead to conclusions that seem opposite to that expected (37). ...
Article
Muscle quality is typically defined as muscle strength relative to muscle size. Echo intensity has gained popularity as an index of skeletal muscle quality. There is common agreement that muscle size is related to strength at baseline and echo intensity is purported to impact this relationship. Thus, the purpose of this study was to examine whether echo intensity can be used as a physiological marker for muscle quality by investigating the moderating effect of echo intensity on the relationship between muscle size and strength. A sample of 96 participants was used for the upper body analysis and a separate sample of 96 participants was used for the lower body analysis. Echo intensity, muscle thickness, and strength measurements were measured on each limb. For strength, participants performed unilateral elbow flexion (upper body analysis) and knee extension (lower body analysis) to quantify 1-repetition maximum. Muscle thickness and echo intensity were determined from images captured using B-mode ultrasound. Muscle size correlated with muscle strength for all limbs. However, the relationship between muscle size and strength was not significantly moderated by echo intensity for Arm 1 (b = 0.042, p = 0.54) or Arm 2 (b = -0.002, p = 0.97). At the proximal site, no significant moderating effect of echo intensity was found in Leg 1 (b = 0.037, p = 0.67) or Leg 2 (b = -0.085, p = 0.29). Similarly, no significant moderating effect was observed at the distal site for Leg 1 (b = 0.03, p = 0.69) or Leg 2 (b = -0.026, p = 0.75). The results would indicate that the relationship between muscle size and strength does not depend on echo intensity. Therefore, the use of echo intensity as an index of muscle quality in healthy young adults may need to be reconsidered.
... In clinical practice, open (seated knee extension, straight leg raise etc.) and closed kinetic chain exercises (leg press, squatting, sit-to-stand etc.) are widely used by physiotherapists to strengthen the quadriceps muscle (Kooiker et al., 2014). However, conventional multi-joint, closed kinetic chain exercises have several advantages because both be observed regarding muscle thickness in both eccentric and concentric training (Blazevich et al., 2007;Cadore et al., 2014;Franchi et al., 2015;Santos et al., 2018;Timmins et al., 2016). It is thought that these contradictory results may arise from the different evaluation methods used (Roig et al., 2009). ...
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Background: In clinical practice, resistance training, which includes concentric and eccentric dynamic muscle movements, is widely used by physiotherapists to strengthen the quadriceps muscle. However, although eccentric training is assumed to induce greater hypertrophy compared to concentric contractions, there are also studies reporting that similar increases in muscle thickness can be seen in both eccentric and concentric training. Objective: This study aims to assess the effect of the eccentric and concentric squat exercise on quadriceps thickness, and lower extremity performance during jumping and walking in healthy young sedentary males. Methods: Participants were randomly divided into three groups: concentric exercise group (CE; n = 19), eccentric exercise group (EE; n = 13) and control group (CG; n = 16). Both exercises were performed seven days a week, for eight weeks with a gradual strength increase. The CG was not given any exercise. Ultrasound assessment of quadriceps muscle thickness, performance in Six-Minute Walk Test and vertical jump was measured. Results: Thickness of dominant side of rectus femoris (p = .008) and vastus lateralis (p = .021) differed significantly among the three groups; post hoc analysis revealed the thickness of rectus femoris in CG was significantly lower than in the CE (p = .046) and EE (p = .006) and the thickness of vastus lateralis in the EE was significantly higher than in the CG (p = .018). Six-Minute Walk Test score in the EE was significantly higher than in the CG (p = .025) and the vertical jump score in the CG significantly lower than in the EE (p = .002) and CE (p < .001). Conclusions: Eccentric and concentric training both benefits muscle hypertrophy and lower extremity functional performance. However, eccentric training also appears to offer a small advantage over concentric training. Keywords: muscle contraction, isotonic contraction, muscle hypertrophy, functional performances, ultrasonography
... We were only able to find one other study reporting the relationship between relative changes in isometric and isokinetic strength (although it is likely that additional reports exist). That study, which was conducted in a young adult population, reported that resistance exerciseinduced relative change in isometric leg extension strength explained 44% of the variance in the relative change in isokinetic strength (at 60 • / s) (Cadore et al., 2014). Accordingly, we reached out to several authors of articles who measured isometric and isokinetic strength following resistance exercise and asked them to analyze their data for the relationship between the relative changes in isometric and isokinetic strength. ...
Article
Background Older adults display wide individual variability (heterogeneity) in the effects of resistance exercise training on muscle strength. The mechanisms driving this heterogeneity are poorly understood. Understanding of these mechanisms could permit development of more targeted interventions and/or improved identification of individuals likely to respond to resistance training interventions. Thus, this study assessed potential physiological factors that may contribute to strength response heterogeneity in older adults: neural activation, muscle hypertrophy, and muscle contractility. Methods In 24 older adults (72.3 ± 6.8 years), we measured the following parameters before and after 12 weeks of progressive resistance exercise training: i) isometric leg extensor strength; ii) isokinetic (60°/sec) leg extensor strength; iii) voluntary (neural) activation by comparing voluntary and electrically-stimulated muscle forces (i.e., superimposed doublet technique); iv) muscle hypertrophy via dual-energy x-ray absorptiometry (DXA) estimates of regional lean tissue mass; and v) intrinsic contractility by electrically-elicited twitch and doublet torques. We examined associations between physiological factors (baseline values and relative change) and the relative change in isometric and isokinetic muscle strength. Results Notably, changes in quadriceps contractility were positively associated with the relative improvement in isokinetic (r = 0.37–0.46, p ≤ 0.05), but not isometric strength (r = 0.09–0.21). Change in voluntary activation did not exhibit a significant association with the relative improvements in either isometric or isokinetic strength (r = 0.35 and 0.33, respectively; p > 0.05). Additionally, change in thigh lean mass was not significantly associated with relative improvement in isometric or isokinetic strength (r = 0.09 and −0.02, respectively; p > 0.05). Somewhat surprising was the lack of association between exercise-induced changes in isometric and isokinetic strength (r = 0.07). Conclusions The strength response to resistance exercise in older adults appears to be contraction-type dependent. Therefore, future investigations should consider obtaining multiple measures of muscle strength to ensure that strength adaptations are comprehensively assessed. Changes in lean mass did not explain the heterogeneity in strength response for either contraction type, and the data regarding the influence of voluntary activation was inconclusive. For isokinetic contraction, the strength response was moderately explained by between-subject variance in the resistance-exercise induced changes in muscle contractility.
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High‐load eccentric training reputedly produces greater muscle hypertrophy than concentric training, possibly due to greater loading and/or inflammation. We quantified the temporal impact of combined maximal concentric‐eccentric training vs maximal concentric training on muscle cross‐sectional area (CSA), volume and targeted mRNA expression (93 transcripts). Eight recreationally active males (24±5 years, BMI 23.5±2.5 kg/m2) performed 3x30 maximal eccentric isokinetic knee extensions and 2x30 maximal concentric knee extensions in dominant limb (ECC+CON) and 5x30 maximal concentric contractions (CON) in the non‐dominant limb for 12 weeks (all 90°/s, 3x/week). Quadriceps muscle CSA and volume were measured at baseline, 28 days (d) and 84d in both limbs (3T MRI). Resting vastus lateralis biopsies were obtained from both limbs at baseline, 24 hours (h), 7d, 28d and 84d for mRNA abundance measurements (RT‐PCR microfluidic cards). Work output was greater throughout training in ECC+CON vs CON (20.8±9.7%, p<0.001). Muscle CSA increased from baseline in both limbs at 28d (CON 4.3±2.6%, ECC+CON 4.0±1.9%, both p<0.001) and 84d (CON 3.9±2.3%, ECC+CON 4.0±3.1%, both p<0.001), and muscle volume and isometric strength at 84d (CON 44.8±40.0%, p<0.001; ECC+CON 36.9 ± 40.0%, p<0.01), but no between‐limb differences existed in any parameter. Ingenuity Pathway Analysis identified several cellular functions associated with regulation of muscle mass and metabolism as altered by both modalities at 24h and 7d, but particularly with ECC+CON. However, mRNA responses waned thereafter, regardless of modality. Initial muscle mRNA responses to training did not reflect chronic training‐induced hypertrophy. Moreover, ECC+CON did not produce greater hypertrophy than CON, despite greater loading throughout and a differential mRNA response during the initial training week.
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Background: Skeletal muscle contractions are caused to release myokines by muscle fiber. This study investigated the myogenic regulatory factors, as MHC I, IIA, IIX, Myo-D, MRF4, Murf, Atrogin-1, Decorin, Myonection, and IL-15 mRNA expression in the response of eccentric vs. concentric contraction. Methods: Eighteen healthy men were randomly divided into two eccentric and concentric groups, each of 9 persons. Isokinetic contraction protocols included maximal single-leg eccentric or concentric knee extension tasks at 60°/s with the dominant leg. Contractions consisted of a maximum of 12 sets of 10 reps, and the rest time between each set was 30 seconds. The baseline biopsy was performed four weeks before the study, and post-test biopsies were taken immediately after exercise protocols from Vastus Lateralis muscle. The gene expression levels evaluated using Real-Time PCR methods. Results: A significant difference in MyoD, MRF4, Myonection, and Decorin mRNA, were observed following eccentric or concentric contractions (P≤0.05). The MHC I, MHC IIA, IL-15 mRNA has been changed significantly compared to the pre-exercise in the concentric group (P≤0.05). While only MHC IIX and Atrogin-1 mRNA changed significantly in the eccentric group (P≤0.05). Additionally, the results showed a significant difference in MyoD, MRF4, IL-15, and Decorin were observed at the follow-up values between eccentric or concentric groups (P≤0.05). Conclusion: Our findings highlight the growing importance of elucidating the different responses of muscle growth factors associated with a myogenic activity such as MHC IIA, Decorin, IL-15, Myonectin, Decorin, MuRF1, and MHC IIX mRNA in following to various types of exercise.
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Purpose: Motor unit conduction velocity (MUCV) represents the propagation velocity of action potentials along the muscle fibres innervated by individual motor neurons and indirectly reflects the electrophysiological properties of the sarcolemma. In this study, we investigated the effect of a 4-week strength training intervention on the peripheral properties (MUCV and motor unit action potential amplitude, RMSMU) of populations of longitudinally tracked motor units (MUs). Methods: The adjustments exhibited by 12 individuals who participated in the training (INT) were compared with 12 controls (CON). Strength training involved ballistic (4x10) and sustained (3x10) isometric ankle dorsi flexions. Measurement sessions involved the recordings of maximal voluntary isometric force (MViF) and submaximal isometric ramp contractions, while high-density surface EMG (HDsEMG) was recorded from the tibialis anterior. HDsEMG signals were decomposed into individual MU discharge timings and MUs were tracked across the intervention. Results: MViF (+14.1%, P=0.003) and average MUCV (+3.00%, P=0.028) increased in the INT group, while normalized MUs recruitment threshold (RT) decreased (-14.9%, P=0.001). The slope (rate of change) of the regression between MUCV and MUs RT increased only in the INT group (+32.6%, P=0.028), indicating a progressive greater increase in MUCV for higher-threshold MUs. The intercept (initial value) of MUCV did not change following the intervention (P=0.568). The association between RMSMU and MUs RT was not altered by the training. Conclusion: The increase in the rate of change in MUCV as a function of MU recruitment threshold, but not the initial value of MUCV, suggests that short-term strength training elicits specific adaptations in the electrophysiological properties of the muscle fibre membrane in high-threshold motor units.
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Objective Recumbent rest elicits a decrease in muscle size of the lower extremity, but the extent of decrease may be related to differences in muscle quality. This could have implications for ultrasound-derived measures of muscle size, particularly in individuals with a large proportion of intramuscular contractile elements. The research objective was to determine whether decreases in muscle size following recumbent rest are related to ultrasound-derived corrected echo intensity in resistance-trained males. Methods Cross-sectional area (CSA), echo intensity (EI), subcutaneous fat thickness (SFT), and EI corrected for SFT (EI Cor ) of the vastus lateralis (VL) were measured via ultrasonography in 30 resistance-trained males. Measures were obtained immediately following recumbency (T0) and 15 minutes after recumbency (T15). The association between EI Cor and percentage change in CSA (%ΔCSA) from T0 to T15 was examined. Comparisons of morphological characteristics were examined between a subset of participants with the lowest (LO; n = 10; <33rd percentile) and highest (HI; n = 10; >66th percentile) EI Cor . Results EI Cor was not correlated with %ΔCSA ( P = .151), and the decrease in CSA from T0 to T15 did not differ between the LO and HI groups. Conclusions Muscle quality (EI Cor ) is not related to the decrease in CSA of the VL following recumbent rest among resistance-trained, young males. The time frame of muscle CSA acquisition should not differ based solely on differences in muscle quality.
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Exercise is important for prevention of sarcopenia in the elderly population. We tested two training modalities, ascending or descending stair walking, representing concentric (CON) and eccentric (ECC) exercise, respectively. We also tested the effects of additional weight during eccentric exercise (ECC+). Thirty-two healthy men and women (70±3 [mean ± SE] yrs.) were randomly assigned to CON, ECC, or ECC+ (carrying +15 % of body weight in a vest) in a 3 (n=32) or 6 (n=21) week intervention (3 sessions/week). Data was analysed by mixed models approach. Rate of perceived exertion (RPE; Borg scale 6-20; mean values from 3 and 6weeks) during training did not differ between CON (12.3±0.4), ECC (11.5±0.3), and ECC+ (11.7±0.4). After 6weeks, leg muscle mass increased more in ECC+ (+0.29±0.09 kg) vs CON (+0.08±0.05 kg) (P<0.05) but not different from ECC (+0.16±0.06 kg). 6-minute walk test (6MWT) increased after 6 weeks more (P<0.05) in ECC+ (+85±23 m) compared with ECC (+37±13 m) and CON (+27±12 m). Intramyocellular glycogen content increased from 359±19 nmol/mg d.w. in CON (to 511±65 and 471±44 after 3 and 6 wks, respectfully (P<0.05)), but not in ECC (to 344±28 after 6 weeks) or in ECC+ (to 389±20 after 6 weeks). Conclusion: carrying extra weight while descending stair walking do not increase RPE, but the ECC+ training resulted in greater muscle responses compared with CON, but glycogen synthesis was stimulated only in CON. Descending stairs is a simple model for prevention and treatment of sarcopenia and the stimulus is enhanced by carrying extra weights.
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Background Reductions in muscle size are common after anterior cruciate ligament reconstruction (ACLR) and may contribute to suboptimal patient outcomes. However, few studies have quantified postoperative alterations in muscle quality and evaluated its associations with patient-reported function. Hypotheses Rectus femoris cross-sectional area (CSA) will decrease postoperatively but improve at return to activity (RTA), rectus femoris muscle quality (percentage fat [PF]) will increase postoperatively and be greater at RTA compared with preoperative values, and rectus femoris CSA and PF will be associated with International Knee Documentation Committee (IKDC) scores at both postoperative time points. Study Design Case series. Level of Evidence Level 4. Methods A total of 26 individuals who sustained an ACL injury and underwent reconstructive surgery were evaluated preoperatively (T 0 ), 9 weeks post-ACLR (T 1 ), and at RTA. Rectus femoris CSA and PF were evaluated bilaterally via ultrasound imaging, and patient-reported function was assessed using the IKDC score. Results Bilateral reductions in rectus femoris CSA were noted from T 0 to T 1 ( P < 0.01). Only the uninvolved limb returned to preoperative CSA ( P = 0.80), as the involved limb failed to return to preoperative levels at RTA ( P = 0.04). No significant changes in rectus femoris PF were observed across time points ( P > 0.05). Lesser PF ( P < 0.01) but not CSA ( P = 0.75) was associated with higher IKDC score at T 1 . Lesser PF ( P = 0.04) and greater CSA ( P = 0.05) was associated with higher IKDC score at RTA. Conclusion Substantial atrophy occurs bilaterally after ACLR, and the involved limb does not return to preoperative muscle size despite the patient completing rehabilitation. Quadriceps muscle morphology is associated with patient-reported function and may be an important rehabilitation target after ACLR. Clinical Relevance Quadriceps atrophy and poor muscle quality may contribute to suboptimal patient functioning and quadriceps dysfunction and may be important in RTA decision making. Assessing muscle morphology using ultrasound may be a feasible and clinically beneficial tool in patients after ACLR.
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Individual skeletal muscle fibers have been used to examine a wide variety of cellular functions and pathologies. Among other parameters, skeletal muscle action potential propagation has been measured to assess the integrity and function of skeletal muscle. In this paper, we utilize Di-8-ANEPPS, a potentiometric dye and mag-fluo-4, a low-affinity intracellular calcium indicator to non-invasively and reliably measure action potential conduction velocity in skeletal muscle. We used an extracellular bipolar electrode to generate an electric field that will initiate an action potential at one end of the fiber or the other. Using enzymatically dissociated flexor digitorum brevis (FDB) fibers, we demonstrate the strength and applicability of this technique. Using high-speed line scans, we estimate the conduction velocity to be approximately 0.4 m/s. In addition to measuring the conduction velocity, we can also measure the passive electrotonic potentials elicited by pulses by either applying tetrodotoxin (TTX) or reducing the bath sodium levels. We applied these methodologies to FDB fibers under elevated extracellular potassium conditions, and found that the conduction velocity is significantly reduced compared to our control concentration. Lastly, we have constructed a circuit model of a skeletal muscle in order to predict passive polarization of the fiber by the field stimuli. Our predictions from the model fiber closely resemble the recordings acquired from in vitro assays. With these techniques, we can examine how many different pathologies and mutations affect skeletal muscle action potential propagation. Our work demonstrates the utility of using Di-8-ANEPPS or mag-fluo-4 to non-invasively measure action potential conduction velocity.
To investigate the efficacy of exercise intervention using a real-time video conferencing platform (ZOOM) on inter-recti distance, abdominal muscle thickness, static trunk endurance, and maternal quality of life, 37 women with diastasis recti between six months and one year postpartum were randomly divided into the online (n = 19) and offline (n = 18) groups. The online group underwent 40-min trunk stabilization exercise sessions twice a week for six weeks, through a real-time video conference platform, while the offline group attended the same program in person. The inter-recti distance and muscle thickness between the abdominal muscles were measured by rehabilitation ultrasound imaging, the Torso endurance test was used to compare the static trunk endurance, and the maternal quality of life questionnaire (MAPP-QOL, score) was applied. Significant improvements were observed in the inter-recti distance between the rectus abdominis, abdominal muscle thickness, static trunk endurance, and maternal quality of life in both groups (p < 0.001); a more significant improvement was observed in the offline group. No significant differences were observed between groups except for the left rectus abdominis thickness and Psychological/Baby and Relational/Spouse-Partner subscale in the maternal quality of life index (p > 0.05). Exercise interventions delivered in a real-time videoconferencing platform are effective at improving the inter-recti distance, trunk stability, and quality of life in postpartum women and may be an alternate to face-to-face intervention.
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The aim of the study was to verify whether 8 weeks of resistance training employing maximal isokinetic eccentric (IERT) knee extensor actions would reduce the acute force loss observed after high-intensity treadmill running exercise. It was hypothesized that specific IERT would induce protective effects against muscle fatigue and ultrastructural damages, preventing or reducing the loss in mechanical muscle function after running. Subjects were tested before and after IERT protocol for maximal isometric, concentric and eccentric isokinetic knee extensor strength (60° and 180° s(-1)). In a second session, subjects performed treadmill running (~35 min) and the previously mentioned measurements were repeated immediately after running. Subsequently, subjects were randomized to training (n = 12) consisting of 24 sessions of maximal IERT knee extensors actions at 180° s(-1), or served as controls (n = 8). The effects of acute running-induced fatigue and training on isokinetic and isometric peak torque, and rate of force development (RFD) were investigated. Before IERT, running-induced eccentric torque loss at 180° s(-1) was -8 %, and RFD loss was -11 %. Longitudinal IERT led to reduced or absent acute running-induced losses in maximal IERT torque at 180° s(-1) (+2 %), being significantly reduced compared to before IERT (p < 0.05), however, RFD loss remained at -11 % (p > 0.05). In conclusion, IERT yields a reduced strength loss after high-intensity running workouts, which may suggest a protective effect against fatigue and/or morphological damages. However, IERT may not avoid reductions in explosive muscle actions. In turn, this may allow more intense training sessions to be performed, facilitating the adaptive response to running training.
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The aim of this study was to compare the effects of low- and high-volume strength training on strength, muscle activation and muscle thickness (MT) of the lower- and upper-body, and on muscle quality (MQ) of the lower-body in older women. Twenty apparently healthy elderly women were randomly assigned into two groups: low-volume (LV, n=11) and high-volume (HV, n=9). The LV group performed one-set of each exercise, while the HV group performed three-sets of each exercise, twice weekly for 13 weeks. MQ was measured by echo intensity obtained by ultrasonography (MQEI), strength per unit of muscle mass (MQST), and strength per unit of muscle mass adjusted with an allometric scale (MQAS). Following training, there was a significant increase (p≤0.001) in knee extension 1-RM (31.8 ± 20.5% for LV and 38.3 ± 7.3% for HV) and in elbow flexion 1-RM (25.1 ± 9.5% for LV and 26.6 ± 8.9% for HV) and in isometric maximal strength of the lower-body (p≤0.05) and upper-body (p≤0.001), with no difference between groups. The maximal electromyographic activation for both groups increased significantly (p≤0.05) in the vastus medialis and biceps brachii, with no difference between groups. All MT measurements of the lower- and upper-body increased similarly in both groups (p≤0.001). Similar improvements were also observed in MQEI (p≤0.01), MQST, and MQAS (p≤0.001) for both groups. These results demonstrate that low- and high-volume strength training promote similar increases in neuromuscular adaptations of the lower- and upper-body, and in MQ of the lower-body in elderly women.
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This study investigated the chronology of neural and morphological adaptations to knee extensor eccentric training and their contribution to strength gains in isometric, concentric and eccentric muscle actions. 20 male healthy subjects performed a 12-week eccentric training program on an isokinetic dynamometer, and neuromuscular evaluations of knee extensors were performed every 4 weeks. After 12 training weeks, significant increases were observed for: isometric (24%), concentric (15%) and eccentric (29%) torques; isometric (29%) and eccentric (33%) electromyographic activity; muscle thickness (10%) and anatomical cross-sectional area (19%). Eccentric and isometric torques increased progressively until the end of the program. Concentric torque and muscle mass parameters increased until the eighth training week, but did not change from this point to the twelfth training week. Eccentric and isometric activation increased at 4 and 8 training weeks, respectively, while no change was found in concentric activation. These results suggest that: 1) the relative increment in concentric strength was minor and does not relate to neural effects; 2) eccentric and isometric strength gains up to 8 training weeks are explained by the increased neural activation and muscle mass, whereas the increments in the last 4 training weeks seem to be associated with other mechanisms.
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Purpose: The purpose of this study was to compare neuromuscular adaptations induced by work-matched isoload (IL) versus isokinetic (IK) eccentric resistance training. Methods: A total of 31 healthy subjects completed a 9-wk IL (n = 11) or IK (n = 10) training program for the knee extensors or did not train (control group; n = 10). The IL and IK programs consisted of 20 training sessions, which entailed three to five sets of eight repetitions in the respective modalities. The amount of work and the mean angular velocity were strictly matched between IL and IK conditions. Neuromuscular tests were performed before and after training and consisted of the assessment of quadriceps muscle strength, muscle architecture (vastus lateralis), EMG activity, and antagonist coactivation. Results: IL, but not IK, eccentric resistance training enhanced eccentric strength at short muscle length (+20%), high-velocity eccentric strength (+15%), muscle thickness (+10%), and fascicle angle measured at rest (+11%; P < 0.05). Agonist EMG activity increased almost similarly for the two modalities, whereas antagonist coactivation was unaffected by training. Conclusions: IL proved to be more effective than IK training for improving quadriceps muscle strength and structure. It is conjectured that the rapid acceleration of the load in the early phase of IL eccentric movements (i.e., at short muscle lengths), which results in greater torque and angular velocities compared with IK actions, is the main determinant of strength and neuromuscular adaptations to eccentric training. These findings have important consequences for the optimization of IL and IK eccentric exercise for resistance training and rehabilitation purposes.
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The purpose of the present study was to investigate the effect of supplemental heavy strength training on muscle thickness and determinants of performance in well-trained Nordic Combined athletes. Seventeen well-trained Nordic Combined athletes were assigned to either usual training supplemented with heavy strength training (STR; n = 8) or to usual training without heavy strength training (CON; n = 9). The strength training performed by STR consisted of one lower-body exercise and two upper-body exercises [3-5 repetition maximum (RM) sets of 3-8 repetitions], which were performed twice a week for 12 weeks. Architectural changes in m. vastus lateralis, 1RM in squat and seated pull-down, squat jump (SJ) height, maximal oxygen consumption (VO(2max)), work economy during submaximal treadmill skate rollerskiing, and performance in a 7.5-km rollerski time trial were measured before and after the intervention. STR increased 1RM in squat and seated pull-down, muscle thickness, and SJ performance more than CON (p < 0.05). There was no difference between groups in change in work economy. The two groups showed no changes in total body mass, VO(2max), or time-trial performance. In conclusion, 12 weeks of supplemental strength training improved determinants of performance in Nordic Combined by improving the athletes' strength and vertical jump ability without increasing total body mass or compromising the development of VO(2max).
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The present study aimed to compare muscle architecture and electromyographic activity during isotonic (IT) and isokinetic (IK) knee extensors eccentric contractions. Seventeen subjects were assigned in test and reproducibility groups. During test session, subjects performed two IT and two IK sets of eccentric contractions of knee extensor muscles. Torque, angular velocity, VL architecture and EMG activity of agonist (vastus lateralis, VL; vastus medialis; rectus femoris) and antagonist (semitendinosus; biceps femoris, BF) muscles were simultaneously recorded and averaged on a 5° window. Torque-angle and angular velocity-angle relationships exhibited differences in mechanical load between the IT and IK modes. Changes in muscle architecture were similar in both modes, since VL fascicles length increased and fascicle angle decreased, resulting in a decrease in muscle thickness during eccentric contraction. Agonist activity and BF co-activity levels were higher in IT mode than in IK mode at short muscle lengths, whereas agonist activity was higher in IK mode than in IT mode at long muscle lengths. Differences in mechanical load between both modes induced specific neuromuscular responses in terms of agonist activity and antagonist co-activity. These results suggest that specific neural adaptations may occur after IT or IK eccentric training. This hypothesis needs to be tested in order to gain new insights concerning the most effective eccentric protocols based on whether the objective is sportive or clinical.
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It has been shown that mean muscle fiber conduction velocity (CV) can be acutely impaired after eccentric exercise. However, it is not known whether this applies to other exercise modes. Therefore, the purpose of this experiment was to compare the effects of eccentric and concentric exercises on CV, and amplitude and frequency content of surface electromyography (sEMG) signals up to 24 h post-exercise. Multichannel sEMG signals were recorded from biceps brachii muscle of the exercised arm during isometric maximal voluntary contraction (MVC) and electrically evoked contractions induced by motor-point stimulation before, immediately after and 2 h after maximal eccentric (ECC group, N = 12) and concentric (CON group, N = 12) elbow flexor exercises. Isometric MVC decreased in CON by 21.7 ± 12.0% (± SD, p < 0.01) and by 30.0 ± 17.7% (p < 0.001) in ECC immediately post-exercise when compared to baseline. At 2 h post-exercise, ECC showed a reduction in isometric MVC by 24.7 ± 13.7% (p < 0.01) when compared to baseline, while no significant reduction (by 8.0 ± 17.0%, ns) was observed in CON. Similarly, reduction in CV was observed only in ECC both during the isometric MVC (from baseline of 4.16 ± 0.3 to 3.43 ± 0.4 m/s, p < 0.001) and the electrically evoked contractions (from baseline of 4.33 ± 0.4 to 3.82 ± 0.3 m/s, p < 0.001). In conclusion, eccentric exercise can induce a greater and more prolonged reduction in muscle force production capability and CV than concentric exercise.
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The quest to increase lean body mass is widely pursued by those who lift weights. Research is lacking, however, as to the best approach for maximizing exercise-induced muscle growth. Bodybuilders generally train with moderate loads and fairly short rest intervals that induce high amounts of metabolic stress. Powerlifters, on the other hand, routinely train with high-intensity loads and lengthy rest periods between sets. Although both groups are known to display impressive muscularity, it is not clear which method is superior for hypertrophic gains. It has been shown that many factors mediate the hypertrophic process and that mechanical tension, muscle damage, and metabolic stress all can play a role in exercise-induced muscle growth. Therefore, the purpose of this paper is twofold: (a) to extensively review the literature as to the mechanisms of muscle hypertrophy and their application to exercise training and (b) to draw conclusions from the research as to the optimal protocol for maximizing muscle growth.
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The study investigated changes in motor output and motor unit behavior following 6 wk of either strength or endurance training programs commonly used in conditioning and rehabilitation. Twenty-seven sedentary healthy men (age, 26.1 ± 3.9 yr; mean ± SD) were randomly assigned to strength training (ST; n = 9), endurance training (ET; n = 10), or a control group (CT; n = 8). Maximum voluntary contraction (MVC), time to task failure (isometric contraction at 30% MVC), and rate of force development (RFD) of the quadriceps were measured before (week 0), during (week 3), and after a training program of 6 wk. In each experimental session, surface and intramuscular EMG signals were recorded from the vastus medialis obliquus and vastus lateralis muscles during isometric knee extension at 10 and 30% MVC. After 6 wk of training, MVC and RFD increased in the ST group (17.5 ± 7.5 and 33.3 ± 15.9%, respectively; P < 0.05), whereas time to task failure was prolonged in the ET group (29.7 ± 13.4%; P < 0.05). The surface EMG amplitude at 30% MVC force increased with training in both groups, but the training-induced changes in motor unit discharge rates differed between groups. After endurance training, the motor unit discharge rate at 30% MVC decreased from 11.3 ± 1.3 to 10.1 ± 1.1 pulses per second (pps; P < 0.05) in the vasti muscles, whereas after strength training it increased from 11.4 ± 1.2 to 12.7 ± 1.3 pps (P < 0.05). Finally, motor unit conduction velocity during the contractions at 30% MVC increased for both the ST and ET groups, but only after 6 wk of training (P < 0.05). In conclusion, these strength and endurance training programs elicit opposite adjustments in motor unit discharge rates but similar changes in muscle fiber conduction velocity.
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The aim of the present study was to investigate the effects of concurrent strength and endurance training on neuromuscular and hormonal parameters in elderly men. 23 healthy men (65±4 years) were randomly assigned to 1 of 3 groups: concurrent (CG, n=8), strength (SG, n=8) or endurance group (EG, n=7). The programs consisted, of strength training, endurance training on a cycle ergometer or a combination of both in the same session 3 times per week over a duration of 12 weeks. Subjects were evaluated on parameters related to muscle strength, muscle activation and serum hormones. There were significant increases in lower-body strength in all groups (P<0.05), with higher increases in SG (67%) than CG (41%) and both were higher than EG (25%) (p<0.01). Only SG and CG increased upper-body strength (p<0.01), with no significant difference between the 2 groups. Furthermore, there were significant decreases in free testosterone in EG after training. Significant increases in isometric strength and maximal muscle activation (p<0.05) as well as decreases in the submaximal muscle activation to the same load, were only seen in SG (p<0.05). The present results suggest that the interference effect observed due to concurrent strength and endurance training could be related to impairment of neural adaptations.
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The purpose of this study was to examine the reliability and validity of the "panoramic" brightness mode ultrasonography (US) method to detect training-induced changes in muscle cross-sectional area (CSA) by comparison with results obtained using magnetic resonance imaging (MRI). Out of 27 young male volunteers, 20 subjects were assigned to training group and seven to non-training control group. Muscle CSAs of vastus lateralis were analyzed by MRI and US before and after 21 weeks of either heavy resistance training or control period. Measured by both the US and MRI, the resistance training induced significant increases (~13-14%, P < 0.001) in muscle CSA, whereas no changes were observed in control group. A high repeatability was found between the two consequent US measurements (intraclass correlation coefficient, ICC of 0.997) with standard error of measurement (SEM) of 0.38 cm(2) and smallest detectable difference of 1.1 cm(2). Validity of the US method against MRI in assessing CSA of VL produced ICC of 0.905 and SEM of 0.87 cm(2) with high limits of agreement analyzed by Bland and Altman method. However, the MRI produced systematically (10 +/- 4%, P < 0.01) larger CSA values than the US method. The US showed high agreement against MRI in detecting changes in muscle CSA (ICC of 0.929, SEM of 0.94 cm(2)). The results of this study showed that the panoramic US method provides repeatable measures of a muscle CSA although MRI produced larger absolute CSA values. Moreover, this US method detects training-induced changes in muscle CSA with a comparable degree of precision to MRI.
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The aim of this systematic review was to determine if eccentric exercise is superior to concentric exercise in stimulating gains in muscle strength and mass. Meta-analyses were performed for comparisons between eccentric and concentric training as means to improve muscle strength and mass. In order to determine the importance of different parameters of training, subgroup analyses of intensity of exercise, velocity of movement and mode of contraction were also performed. Twenty randomised controlled trials studies met the inclusion criteria. Meta-analyses showed that when eccentric exercise was performed at higher intensities compared with concentric training, total strength and eccentric strength increased more significantly. However, compared with concentric training, strength gains after eccentric training appeared more specific in terms of velocity and mode of contraction. Eccentric training performed at high intensities was shown to be more effective in promoting increases in muscle mass measured as muscle girth. In addition, eccentric training also showed a trend towards increased muscle cross-sectional area measured with magnetic resonance imaging or computerised tomography. Subgroup analyses suggest that the superiority of eccentric training to increase muscle strength and mass appears to be related to the higher loads developed during eccentric contractions. The specialised neural pattern of eccentric actions possibly explains the high specificity of strength gains after eccentric training. Further research is required to investigate the underlying mechanisms of this specificity and its functional significance in terms of transferability of strength gains to more complex human movements.
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Our previous study showed that relatively low-intensity (approximately 50% one-repetition maximum [1RM]) resistance training (knee extension) with slow movement and tonic force generation (LST) caused as significant an increase in muscular size and strength as high-intensity (approximately 80% 1RM) resistance training with normal speed (HN). However, that study examined only local effects of one type of exercise (knee extension) on knee extensor muscles. The present study was performed to examine whether a whole-body LST resistance training regimen is as effective on muscular hypertrophy and strength gain as HN resistance training. Thirty-six healthy young men without experience of regular resistance training were assigned into three groups (each n = 12) and performed whole-body resistance training regimens comprising five types of exercise (vertical squat, chest press, latissimus dorsi pull-down, abdominal bend, and back extension: three sets each) with LST (approximately 55-60% 1RM, 3 seconds for eccentric and concentric actions, and no relaxing phase); HN (approximately 80-90% 1RM, 1 second for concentric and eccentric actions, 1 second for relaxing); and a sedentary control group (CON). The mean repetition maximum was eight-repetition maximum in LST and HN. The training session was performed twice a week for 13 weeks. The LST training caused significant (p < 0.05) increases in whole-body muscle thickness (6.8 +/- 3.4% in a sum of six sites) and 1RM strength (33.0 +/- 8.8% in a sum of five exercises) comparable with those induced by HN training (9.1 +/- 4.2%, 41.2 +/- 7.6% in each measurement item). There were no such changes in the CON group. The results suggest that a whole-body LST resistance training regimen is as effective for muscular hypertrophy and strength gain as HN resistance training.
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Four male subjects aged 23-34 years were studied during 60 days of unilateral strength training and 40 days of detraining. Training was carried out four times a week and consisted of six series of ten maximal isokinetic knee extensions at an angular velocity of 2.09 rad.s-1. At the start and at every 20th day of training and detraining, isometric maximal voluntary contraction (MVC), integrated electromyographic activity (iEMG) and quadriceps muscle cross-sectional area (CSA) assessed at seven fractions of femur length (Lf), by nuclear magnetic resonance imaging, were measured on both trained (T) and untrained (UT) legs. Isokinetic torques at 30 degrees before full knee extension were measured before and at the end of training at: 0, 1.05, 2.09, 3.14, 4.19, 5.24 rad.s-1. After 60 days T leg CSA had increased by 8.5% +/- 1.4% (mean +/- SEM, n = 4, p less than 0.001), iEMG by 42.4% +/- 16.5% (p less than 0.01) and MVC by 20.8% +/- 5.4% (p less than 0.01). Changes during detraining had a similar time course to those of training. No changes in UT leg CSA were observed while iEMG and MVC increased by 24.8% +/- 10% (N.S.) and 8.7% +/- 4.3% (N.S.), respectively. The increase in quadriceps muscle CSA was maximal at 2/10 Lf (12.0% +/- 1.5%, p less than 0.01) and minimal, proximally to the knee, at 8/10 Lf (3.5% +/- 1.2%, N.S.). Preferential hypertrophy of the vastus medialis and intermedius muscles compared to those of the rectus femoris and lateralis muscles was observed.(ABSTRACT TRUNCATED AT 250 WORDS)