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Muscle conduction velocity, strength, neural activity, and morphological changes after eccentric and concentric training
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.
... However, no relationship exists between changes in EI and muscle strength before and after strength training [12][13][14]. There are scattered reports of EI decline after strength training [15,16], and a consensus has not been reached. Therefore, changes in EI may reflect not only changes in muscle strength but also changes in muscle stiffness. ...
... Therefore, a relationship between improvements in EI and muscle strength is expected; however, no consensus has been reached on this to date. Cadore et al. [15] reported improvement in both muscle strength and EI in healthy young individuals who underwent isokinetic training for six weeks. Bassan et al. [12] reported an increase in muscle strength but no change in EI in healthy individuals who underwent resistance training for three weeks. ...
... Decreased EI in the SOL muscle was associated with improved ankle plantarflexion strength. The EI decreases after six weeks of strength training in healthy young individuals [15] and after eight weeks of strength training in patients with hip osteoarthritis [16]. Our results support those of previous studies. ...
Objective: We aimed to clarify the relationship between the changes in echo intensity (EI) and Young’s modulus of the soleus (SOL) muscle after ankle fracture surgery.
Methods: Sixteen participants after ankle fracture surgery participated in this study (mean age: 46.8 ± 21.4 years). At three and five months after surgery, ankle range of motion (ROM), ankle strength, SOL muscle EI, and Young’s modulus were measured, and changes in values were calculated. The EI was measured using the B-mode and ImageJ software (National Institutes of Health, Bethesda, MD), and Young’s modulus was measured using shear wave elastography (SWE). The EI values corrected for subcutaneous fat thickness were calculated. Correlation and simple regression analysis were used to clarify the relationship between the amount of change in EI, the amount of change in Young’s modulus, and the amount of change in ankle ROM.
Results: Simple regression analysis showed that the amount of change in EI influenced the amount of change in Young’s modulus of the SOL muscle (r = 0.623; p = 0.010) and the amount of change in ankle dorsiflexion ROM with the knee flexed (r = -0.702; p = 0.002).
Conclusion: The change in EI of the SOL muscle affected the change in Young’s modulus after ankle fracture surgery. Clinically, changes in the EI may reflect changes in muscle stiffness.
... Studies in healthy volunteers and patients with diabetic neuropathy have shown that exercise training (isokinetic [22,23] or hybrid [23]) can improve conduction velocity [22,23] and reduce the incidence of developing motor and sensory neuropathy in the future [24]. The mechanism that exercise can induce changes in the neural status is not fully understood; however, improvements in sleep [25], fatigue [26,27], functional capacity [3], cardiovascular physiology [28], and peripheral neural adjustments to the metabolic changes after training [21], could at least partially explain some of the improvements seen in those patients after the exercise training period. ...
... Studies in healthy volunteers and patients with diabetic neuropathy have shown that exercise training (isokinetic [22,23] or hybrid [23]) can improve conduction velocity [22,23] and reduce the incidence of developing motor and sensory neuropathy in the future [24]. The mechanism that exercise can induce changes in the neural status is not fully understood; however, improvements in sleep [25], fatigue [26,27], functional capacity [3], cardiovascular physiology [28], and peripheral neural adjustments to the metabolic changes after training [21], could at least partially explain some of the improvements seen in those patients after the exercise training period. ...
... Most improved were the lower limb nerves (tibial, peroneal and sural) as expected since the applied aerobic and resistance exercise training involved mainly the leg muscles. More specifically, conduction velocity from tibial and peroneal nerves was improved by 3.7% and 4.2%, respectively, implying that exercise can impose effective stimuli to increase velocity of action potential propagation in muscle fibers and therefore improve muscle strength and reduce fatigability [22] something that has been shown in the present study as well. Slow conduction velocities often seen in many polyneuropathies, have been recognized as an early stage characteristic of uremia-induced neural deficit usually accompanied by a large F-wave latency [7,46]. ...
Introduction and aims
Neurological complications such as peripheral neuropathy are very common in the end-stage renal disease (ESRD) patients, occurring in 60–80% of this specific population. The aim of the present study was to examine whether a 9-month hybrid intradialytic exercise training program could alter motor and sensory nerve conduction study (NCS) parameters in hemodialysis population.
Methods
Seventeen stable patients undergoing HD with no clinical evidence of uremic polyneuropathy were included in the study (15 M/2F, 59 ± 13.7 years). All patients completed a 9-month supervised exercise training program composed of both aerobic cycling and resistance training (hybrid) during HD. Functional capacity was assessed by a battery of tests, while pain levels and fatigue profile were assessed via validated questionnaires. Motor and sensory NCS on bilateral median, ulnar, peroneal and tibial nerves as well as F-wave were assessed using a full neurographic electromyography (EMG) assessment.
Results
After the 9-month exercise training intervention, exercise capacity was increased by 65% and functional capacity by an average of 40%. The neurological assessment showed that conduction velocity from tibial and peroneal nerves was improved by 3.7% and 4.2%, respectively, while tibial F-wave latency and peroneal and sural nerve distal latency were significantly improved by 4.2%, 4.9% and 10%, respectively. Fatigue and pain were improved after the exercise intervention while fatigue score was positively correlated with conduction velocity and amplitude values.
Conclusions
The results of the current study demonstrate that 9-month hybrid exercise training induces beneficial effects on both sensory and motor NCS parameters, improving conduction velocity and F-wave latency. Improvements in neural activity were accompanied by changes in fatigue score and pain-related aspects. The parallel improvement in motor nerve conduction velocity and its correlations with functional tests supports the hypothesis that exercise could be beneficial for preventing a decline in neural function in HD patients.
... 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.). ...
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.
... 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.). ...
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. ...
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.
... 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 . ...
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.
... 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) ...
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.
... 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 ...
... 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. ...
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.
... 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. ...
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%.
... Considerando o amplo escopo de intensidades que pode ser aplicada visando hipertrofia muscular, os profissionais podem prescrever o treinamento a partir de diferentes estratégias visando a obtenção de resultados por seus alunos. Foram desenvolvidos estudos avaliando apenas a fase concêntrica, apenas a fase excêntrica e comparando os resultados dos dois métodos de treino 44,46,47 . Foi observado que ambas as ações produzem resultados na hipertrofia muscular 44,46 , mas foram desenvolvidas pesquisas para investigar qual seria a melhor ação muscular para a hipertrofia. ...
... Foi observado que ambas as ações produzem resultados na hipertrofia muscular 44,46 , mas foram desenvolvidas pesquisas para investigar qual seria a melhor ação muscular para a hipertrofia. Franchi et al. 46 e Cadore et al. 47 ...
As recomendações para o treinamento resistido partem de diretrizes como o ACSM e NSCA para as populações em geral, sendo encorajado a sua prática, a qual leva a benefícios à saúde física e mental. Nessa revisão narrativa, foi analisada a literatura atual sobre as variáveis do treinamento resistido (TR) e sua relação com a hipertrofia muscular, primeiramente, abordando os resultados acerca de cada variável de maneira isolada, posteriormente discutindo os resultados com revisões sistemáticas sobre cada variável isoladamente, e por último, chegando a um consenso do papel de cada variável como um conjunto, e seu impacto na hipertrofia muscular. Em nossos achados encontramos uma relação do volume com a hipertrofia, a frequência como ferramenta para distribuição do volume, um amplo espectro de intensidades que resultam em resultados equivalentes, a ordem e seleção dos exercícios como recurso para hipertrofia localizada, ações excêntricas superiores a ações concêntricas, intervalos como uma maneira de aumentar o volume, e a amplitude de movimento permanece necessitando de mais estudos para relacionar seu papel com a hipertrofia muscular.
... 18 As the amount of fat and fibrous tissue in the muscle decreases, lower EI values are observed. 16,18,19 Thus, this study aimed to investigate the effects of 6-week plyometric training on the sonographic characteristics of the VL including muscle thickness and EI, and PT-CSA, quadriceps strength, and the vertical jump performance of adolescent female volleyball athletes. It was hypothesized that plyometric exercise would increase VL thickness, PT-CSA, quadriceps strength, and vertical jump height but decrease VL-EI in adolescent female volleyball players. ...
... Moreover, previous study showed that 6-week concentric and eccentric trainings reduced VL-EI of in young men and women. 19 Consistent with the findings of Cadore et al., 36 we found a significant decrease in VL-EI for both dominant and nondominant limbs after plyometric training in adolescent female volleyball athletes and the changes exceeded the measurement errors. Larger effects sizes in EI in both limbs showed that plyometric training affected muscle quality more than size. ...
The aim of this study was to investigate the effects of plyometric training on vastus lateralis (VL) and patellar tendon size, quadriceps isokinetic strength, and vertical jump height in adolescent female volleyball players. Thirty players (age mean ± SD : 15.7 ± 1.1 years) participated in a 6-week Sportsmetrics ™ plyometric training program. VL thickness, echo intensity, and patellar tendon cross-sectional area were assessed by real-time ultrasound. Isokinetic quadriceps strength and vertical jump were assessed. The VL thickness, quadriceps strength, and VJ height increased and VL–echo intensity decreased after training. We recommended that 6-week Sportmetrics plyometric training program may be implemented in adolescent female volleyball programs especially before the beginning of the volleyball season.
... 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]. ...
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.
... 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. ...
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 impact of eccentric vs. concentric training on muscle mass and function has been studied previously and mostly in young subjects (Cadore et al., 2014;Franchi et al., 2014;. Franchi et al found no major differences in muscle mass or muscle protein synthesis rates between the two modalities after 10 weeks of training in two small (n = 6) groups of young subjects (Franchi et al., 2014), but in other young subjects the author reported greater phosphorylation of kinases in the MAP kinase family following eccentric exercise (Franchi et al., 2018). ...
... A systematic review in young people (20-33 yr.), focusing on weight-training, documented that gains in muscle mass and strength are higher in exclusively eccentric training compared to concentric training, possibly due to the higher intensity used in eccentric training (Roig et al., 2009). Other studies, with a limited number of subjects in each study (Cadore et al., 2014;Franchi et al., 2014;, overall found no differences in gain of muscle mass or strength between concentric and eccentric traning. ...
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.
... 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. ...
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.
... The role of eccentric loading in enhancing muscle strength has also been tested by prescribing the same external loads, sets, and repetitions in both eccentric-only and concentric-only training [11,24,37,38]. In this instance, the eccentric-only group could theoretically train at a lower relative intensity (i.e., % maximal eccentric strength) due to inherent differences in force-generating capacity between the two muscle action types [39,40]. ...
The principle of specificity suggests that the largest changes in strength occur when training resembles the specific strength test. A one-repetition maximum (1RM) test, which tests the maximal concentric strength, is commonly used as a surrogate for strength adaptation. When separating muscle actions into concentric or eccentric phases, multiple lines of evidence suggest that eccentric muscle actions possess several distinct physiological properties compared with concentric actions. In accordance, there are instances where the increases in 1RM strength test were similar between eccentric-only and concentric-only resistance training. This is at odds with the principle of specificity which suggests that individuals who trained with concentric actions would be expected to have an advantage in that specific task. Although the mechanistic reasons why eccentric-biased training carries over to maximal concentric strength remains to be elucidated, the lack of discernible differences in strength gains with eccentrically-biased training (e.g., eccentric-only and accentuated eccentric training) may imply that the effects of eccentric loading in training are transferable to concentric strength. Our review revisits the role of eccentric loading in enhancing concentric maximal muscle strength. We also speculate on potential physiological factors (i.e., molecular and neural factors) that may differentiate the effects of eccentric and concentric resistance training on the changes in muscle strength. Currently, the majority of the studies investigating the changes in strength have been conducted using isokinetic eccentric training. This is important as there is a viewpoint that the magnitude of chronic adaptations with different modalities of eccentric exercises (i.e., isotonic, isokinetic, and isoinertial training) may also differ from each other. While it has been suggested that eccentric action has a greater transferable capacity for strength adaptations compared to concentric actions, future investigations are warranted to investigate with different modalities of eccentric exercises. There also remains a host of unanswered questions related to the role of eccentric action for maximal concentric strength. For example, future studies may examine whether the eccentric action would be additive when the training is already maximally loaded during the concentric action for increasing concentric maximal strength. We suggested a few different designs that could be used to answer some of these questions in future studies.
... Moreover, ECC session is associated with greater mechanical constraints per skeletal muscle fiber compared with CON power session (71), as evidenced in the present study by the lower muscle activation for a given power output in ECC session compared with CON power session (Fig. 2). Interestingly, muscle hypertrophy is directly stimulated by mechanical constraint per fiber (72); therefore, eccentric exercise leads to greater development of muscle mass and force than concentric exercise (73)(74)(75). Taken together, these findings indicate that eccentric cycling is a promising exercise modality in patients with breast cancer suffering from skeletal muscle atrophy (12). ...
Introduction
This study investigated the magnitude and etiology of neuromuscular fatigue and muscle damage induced by eccentric cycling compared to conventional concentric cycling in patients with breast cancer.
Methods
After a gradual familiarization protocol for eccentric cycling, nine patients with early-stage breast cancer performed three cycling sessions in eccentric or concentric mode. The eccentric cycling session (ECC) was compared to concentric cycling sessions matched for power output (CON power, 80% of concentric peak power output, 95 ± 23 W) or oxygen uptake ( 10 ± 2 mL.min.kg ⁻¹ ). Pre- to postexercise changes (30s through 10 min recovery) in knee extensor maximal voluntary contraction force (MVC), voluntary activation, and quadriceps potentiated twitch force (Q tw ) were quantified to determine global, central, and peripheral fatigue, respectively. Creatine kinase (CK) and lactate dehydrogenase (LDH) activities were measured in the plasma before and 24 h postexercise as markers of muscle damage.
Results
Compared to CON power (-11 ± 9%) and (-5 ± 5%), the ECC session resulted in a greater decrease in MVC (-25 ± 12%) postexercise ( P < 0.001). Voluntary activation decreased only in ECC (-9 ± 6% postexercise, P < 0.001). The decrease in Q tw was similar postexercise between ECC and CON power (-39 ± 21% and -40 ± 16%, P > 0.99) but lower in ( P < 0.001). The CON power session resulted in twofold greater compared to the ECC and sessions ( P < 0.001). No change in CK or LDH activity was reported from preexercise to 24 h postexercise.
Conclusions
The ECC session induced greater neuromuscular fatigue compared to the concentric cycling sessions without generating severe muscle damage. ECC is a promising exercise modality for counteracting neuromuscular maladaptation in patients with breast cancer.
... Effect sizes (Cohen's d) were calculated from mean ± SD changes in the primary variables (strength, ROM, fascicle length, stretch tolerance, energy storage) from previous studies employing similar methods (50)(51)(52). To ensure adequate statistical power for all variables, power analysis was conducted on the variable with the smallest effect size (fascicle length) using the following parameters: β = 0.20, α = 0.05, d = 1.17. ...
Introduction
Large increases in joint range of motion (ROM) have been reported after eccentric resistance training, however limited data exist describing the associated mechanisms or potential cross-education effects in the contralateral limb. Therefore, the effects of a 6-week isokinetic eccentric plantarflexor training program were examined in 26 participants.
Methods
Before and after the training program, dorsiflexion ROM, plantarflexor strength, and muscle-tendon unit (MTU) morphology and mechanics were measured in control ( n = 13) and experimental ( n = 13) young adult groups. Training consisted of 5 sets of 12 maximal isokinetic eccentric plantarflexor contractions twice weekly on the right limb.
Results
Significant ( P < 0.05) increases in dorsiflexion ROM (4.0-9.5°), stretch tolerance (40.3-95.9%), passive elastic energy storage (47.5-161.3%), and isometric (38.1-40.6%) and eccentric (46.7-67.0%) peak plantarflexor torques were detected in both trained and contralateral limbs in the experimental group. Significant increases in gastrocnemius medialis (GM) and soleus thickness (5.4-6.1%), GM fascicle length (7.6 ± 8.5%), passive plantarflexor MTU stiffness (30.1 ± 35.5%) and Achilles tendon stiffness (5.3 ± 4.9%) were observed in the trained limb only. Significant correlations were detected between the changes in trained and contralateral limbs for dorsiflexion ROM ( r = 0.59) and both isometric ( r = 0.79) and eccentric ( r = 0.73) peak torques. No significant changes in any metric were detected in the control group.
Conclusions
Large ROM increases in the trained limb were associated with neurological, mechanical, and structural adaptations, with evidence of a cross-education effect in the contralateral limb being primarily driven by neurological adaptation (stretch tolerance). The large improvements in ROM, muscle size, and strength confirm that isokinetic eccentric training is a highly effective training tool, with potential for use in athletic and clinical populations where MTU function is impaired and current therapies are ineffective.
... In order to assess the EI features of the CM and LC, the images were transferred to offline DICOM ImageJ software version 1.53 (National Institutes of Health, Bethesda, MD, USA) and processed according to previous studies [33,42]. First, all RGB (Red-Green-Blue) images were converted into 256 gray-scale 32-bit images. ...
The aim of this study was to analyze the differences in morphological and histological features of the cervical multifidus (CM) and longus colli (LC) muscles among patients with cervical disc bulging, protrusion, or extrusion. Fifteen patients with cervical disc bulging (20% male, mean age: 48.5, standard deviation (SD) 7.5 years), fifteen with cervical disc protrusion (6% male, mean age: 43, SD 7.8 years), and fifteen with cervical disc extrusion (40% male, mean age: 44, SD 8 years) diagnosed via clinical and imaging findings participated in this study. Additionally, fifteen asymptomatic controls (40% male, mean age: 40.4, SD 9.7 years) were also included. The following ultrasound measurements, cross-sectional area (CSA), anterior–posterior distance (APD), lateral dimension (LD), and mean echo-intensity (EI) of the CM and LC at C5-C6 level were examined by an assessor blinded to the subject’s condition. The results revealed no group ×side significant differences among the groups (p > 0. 00625). However, group effects were found for APD and MEI of the CM (p = 0.006 and p < 0.001, respectively) and CSA, APD and MEI of the LC (all, p < 0.001). The LD of the LC muscle and the APD and LD of the CM were negatively associated with related disability (p < 0.01; p < 0.05 and p < 0.01, respectively), and pain intensity was negatively associated with LC APD and LD (both p < 0.05). These results suggest that US can be used to detect bilateral morphological changes in deep cervical flexors and extensors to discriminate patients with cervical disc alterations.
... However, a previous study also reported that a greater VL cross-sectional area relative to VM is associated with a decreased risk of knee OA 20 and strengthening the lateral muscle knee chain can decrease the load on the medial compartment 21 ; hence, specific intervention programs by selectively strengthening the individual quadriceps and hamstrings seemed to be beneficial in reducing the knee OA risk. The muscle thickness, the fascicle length and the pennation angle increased and the echo intensity reduced following training interventions [22][23][24] . Based on the current study results, strengthening VM can be conflicting in terms of knee joint loading because improved VM was associated with the lower peak KFM and KFM impulse, but greater peak KAMs and KAM impulse at the same time. ...
The purpose of this study was to investigate the relationship between muscular parameters of quadriceps/hamstrings and knee joint kinetics in gait. Muscle architecture (thickness, pennation angle, and fascicle length), and quality (echo intensity) of individual quadriceps and hamstrings of 30 healthy participants (16 males and 14 females) was measured using ultrasound. Peak knee flexion moment (KFM), KFM impulse, peak knee adduction moment (KAM), and KAM impulse during walking were obtained at preferred speed. Pearson’s correlation coefficient and multiple regression analyses were performed at significance level of 0.05, and Cohen’s f² values were calculated to examine the effect sizes of multiple regression. The hamstring-to-quadriceps muscle thickness ratio (r = 0.373) and semitendinosus echo intensity (r = − 0.371) were predictors of first peak KFM (R² = 0.294, P = 0.009, f² = 0.42), whereas only vastus medialis (VM) echo intensity was a significant predictor of second peak KFM (r = 0.517, R² = 0.267, P = 0.003, f² = 0.36). Only the VM thickness was the predictor of first (r = 0.504, R² = 0.254, P = 0.005, f² = 0.34) and second peak KAM (r = 0.581, R² = 0.337, P = 0.001, f² = 0.51), and KAM impulse (r = 0.693, R² = 0.480, P < 0.001, f² = 0.92). In conclusion, the greater hamstring-to-quadriceps muscle thickness ratio and the muscle architecture and quality of medial quadriceps/hamstring play an important role in KFM and KAM, and may have implications in knee osteoarthritis.
... More specifically, the wide variety of movements implemented in PLYO likely did not enable an adequate stimulus for the VL or PFs, while the minimal loading of these muscles in CYC was not conducive to muscle hypertrophy. Interestingly, EI decreased (indicative of improved muscle quality) for both, the VL and PFs, which expands on similar findings following resistance training (Radaelli et al. 2013;Cadore et al. 2014). In contrast to this finding, a previous study found no effect of HIIT on EI (Blue et al. 2018). ...
High-intensity interval training (HIIT) is an effective alternative to moderate intensity continuous training for improvements in body composition and aerobic capacity; however, there is little work comparing different modalities of HIIT. The purpose of this study was to compare the effects of plyometric- (PLYO) and cycle-oriented (CYC) HIIT on body composition, aerobic capacity, and skeletal muscle size, quality, and function in recreationally trained females. Young (21.7 ± 3.1 yrs), recreationally active females were quasi-randomized (1:1 ratio) to 8 weeks of twice weekly PLYO (n = 15) or CYC (n = 15) HIIT. Body composition (four-compartment model), VO2peak, countermovement jump performance, muscle size, and echo intensity (muscle quality), as well as strength and power of the knee extensors and plantar flexors were measured before and after training. Both groups showed a similar decrease in body fat percentage (p < 0.001; η p 2 = 0.409) and echo intensity (p < 0.001; η p 2 = 0.558), and an increase in fat-free mass (p < 0.001; η p 2 = 0.367) and VO2peak (p = 0.001; η p 2 = 0.318). Muscle size was unaffected (p > 0.05), whereas peak torque was reduced similarly in both groups (p = 0.017; η p 2 = 0.188) and rapid torque capacity was diminished only for the knee extensors after CYC (p = 0.022; d = −0.67). These results suggest that PLYO and CYC HIIT are similarly effective for improving body composition, aerobic capacity, and muscle quality, whereas muscle function may express moderate decrements in recreationally active females. ClinicalTrials.gov (NCT05821504)
... It has been reported that eccentric overload exercises could optimize muscle fiber length [14], add sarcomeres in series [15], and increase pennation angle [16], consequently optimizing muscle hypertrophy and strength [17]. Several [18,19] but not all [20,21] studies reported eccentric training to be superior to traditional strength training for muscle mass, strength, and functional performance gains. In addition, eccentric strength training gains could also be specific to the training modality without functional improvements [22]. ...
Background and Objectives: An effective post-injury training program is essential to regain performance and fulfill criteria for return to sport for team sport athletes following anterior cruciate ligament (ACL) reconstruction. The aim of this study was to compare the effects of 6 weeks of eccentric-oriented strength training vs. traditional strength training during the late-stage ACL-rehab phase on leg strength and vertical and horizontal jumping performance in professional team sport athletes. Materials and Methods: Twenty-two subjects (14 males, 8 females, age 19.9 ± 4.4 years, mass 77.4 ± 15.6 kg, height 182.4 ± 11.7 cm) (mean ± SD) with a unilateral reconstructed ACL (BTB graft) were included in the study. All participants enrolled in the same rehabilitation protocol prior to the training study. Players were randomly assigned to an experimental (ECC: n = 11, age 21.8 ± 4.6 years, mass 82.7 ± 16.6 kg, height 185.4 ± 12.2 cm), and a control group (CON: n = 11, age 19.1 ± 2.1 years, mass 76.6 ± 16.5 kg, height 182.5 ± 10.2 cm). Both groups underwent an equivolumed rehabilitation program, with the only difference being in strength training, which consisted of flywheel training vs. traditional strength training for the experimental and control groups, respectively. Testing was organized before and after the 6-week training programs and included isometric semi-squat tests (ISOSI-injured and ISOSU-uninjured legs), vertical jump tests (CMJ), single-leg vertical jump tests (SLJI-injured and SLJU-uninjured legs), single-leg hop tests (SLHI-injured and SLHU-uninjured legs), and triple hop tests (TLHI-injured and TLHU-uninjured legs). In addition, limb symmetry indexes were calculated for the isometric semi-squat (ISOSLSI) test, the single-leg vertical jump (SLJLSI), and the hop (SLHLSI) tests, as well as the triple-leg hop (THLLSI) test. Results: Main effects of time across training were observed for all dependent variables (posttest > pretest, p < 0.05). Significant group-by-time interactions were found for ISOSU (p < 0.05, ES = 2.51, very large), ISOSI (p < 0.05, ES = 1.78, large), CMJ (p < 0.05, ES = 2.23, very large), SLJI (p < 0.05, ES = 1.48, large), SLHI (p < 0.05, ES = 1.83, large), and TLHI (p < 0.05, ES = 1.83, large). Conclusions: This study suggests that eccentric-oriented strength training in late-stage ACL recovery, undertaken twice or three times weekly for 6 weeks, results in better outcomes than traditional strength training in leg strength, vertical jump ability, and single and triple hop tests with injured legs in professional team sport athletes. It seems that flywheel strength training can be recommended in late-stage ACL recovery for professional team sport athletes in order to regain recommended performance outcome levels faster.
... Exercises such as eccentric and concentric training have been reported to improve fatty muscle degeneration [42][43][44][45][46]. Targeted training of the hamstrings, iliopsoas, and hip adductor muscles identified in this study may improve fatty degeneration and be useful to improve HRQoL. ...
Purpose
Artificial intelligence (AI) technologies have enabled precise three-dimensional analysis of individual muscles on computed tomography (CT) or magnetic resonance images via automatic segmentation. This study aimed to perform three-dimensional assessments of pelvic and thigh muscle atrophy and fatty degeneration in patients with unilateral hip osteoarthritis using CT and to evaluate the correlation with health-related quality of life (HRQoL).
Methods
The study included one man and 43 women. Six muscle groups were segmented, and the muscle atrophy ratio was calculated volumetrically. The degree of fatty degeneration was defined as the difference between the mean CT values (Hounsfield units [HU]) of the healthy and affected sides. HRQoL was evaluated using the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index and the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ).
Results
The mean muscle atrophy rate was 16.3%, and the mean degree of muscle fatty degeneration was 7.9 HU. Multivariate correlation analysis revealed that the WOMAC stiffness subscale was significantly related to fatty degeneration of the hamstrings, the WOMAC physical function subscale was significantly related to fatty degeneration of the iliopsoas muscle, and the JHEQ movement subscale was significantly related to fatty degeneration of the hip adductors.
Conclusion
We found that fatty degeneration of the hamstrings, iliopsoas, and hip adductor muscles was significantly related to HRQoL in patients with hip osteoarthritis. These findings suggest that these muscles should be targeted during conservative rehabilitation for HOA and perioperative rehabilitation for THA.
... Following the exercise program, the assigned weekly program was conducted with exercise movements performed according to the difficulty that each individual could perform. In this study, eccentric exercise was performed to activate type 2 muscle fibers [29]. ...
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.
... 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. ...
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), VO 2peak (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. ...
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). ...
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.
... 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. ...
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.
... 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). ...
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
... 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. ...
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.
... 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. ...
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.
... 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. ...
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.
... [26][27][28][29] EI may also signify muscle quality as it is negatively associated with muscle function, strength, and power across populations. 15,17,[30][31][32] Additionally, there is evidence to suggest that EI decreases following chronic resistance training 17,30,[33][34][35] and increases with age, 10,29,30 potentially reflecting changes in the contractile and noncontractile components of muscle. ...
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.
... 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]. ...
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.
... 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. ...
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.
... 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). ...
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.
... 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. ...
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.
... 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. ...
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.
... 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. ...
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), 15 younger women (aged 21 years), 11 older men (aged 74 years), and 15 older women (aged 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.
NoveltyRectus 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 nonuniform across the thigh.
Correction for subcutaneous fat thickness substantially increased EI in women, resulting in greater sex differences.
Background
Improving muscle quality to prevent and treat muscle dysfunction is critical. However, effective measures to improve muscle quality remain poorly understood. We investigated the effects of high- and low-velocity resistance training (RT) on muscle quality, mass, and function before and after an 8-week intervention.
Hypothesis
High-velocity RT would improve muscle quality more effectively than low-velocity RT.
Study Design
Randomized controlled trial.
Level of Evidence
Level 1.
Methods
A total of 33 healthy young women (23.1 ± 2.2 years) were assigned randomly to high-velocity (n = 16) or low-velocity (n = 17) groups. Both groups underwent concentric knee extension RT with a 60% 1-repetition maximum (1RM) load, performing 10 repetitions of 4 sets, 3 times per week for 8 weeks. The high-velocity group was instructed to complete each repetition as quickly as possible (mean repetition duration of 0.5 seconds), while the low-velocity group was required to execute each repetition in 3 seconds. Before and after the 8-week intervention, quadriceps femoris echo intensity (EI), muscle thickness (MT), isokinetic peak torque (60 and 300 deg/s), rate of velocity development (RVD) at 300 deg/s, and 1RM were assessed. Split-plot factorial design analysis of variance was used to compare the group × time interaction.
Results
A group×time interaction was observed for EI ( P < 0.01). Only the high-velocity group showed a significant reduction in EI after the intervention. MT revealed a main effect of time ( P < 0.01), with both groups significantly increasing MT. RVD showed a group × time interaction ( P < 0.05), with significant increase only in the high-velocity group. Isokinetic peak torque and 1RM showed main effects of time ( P < 0.01), with significant increases in both groups.
Conclusion
High-velocity RT may be superior to low-velocity RT in enhancing muscle quality and RVD.
Clinical Relevance
These results emphasize the importance of RT velocity for muscle quality improvement.
Background
Conflicting results have been reported regarding the effects of resistance exercise training with eccentric (lengthening muscle) versus concentric (shortening muscle) contractions on changes in muscle mechanical function assessed by different contraction modes.
Objective
The main objective of this systematic review with meta-analyses was to compare effectiveness of maximal isokinetic eccentric-only and concentric-only strength training for changes in maximal voluntary eccentric (MVCECC), concentric (MVCCON), and isometric contraction (MVCISO) strength in healthy adults.
Methods
We conducted a systematic search in PubMed, SPORTDiscus, and Google Scholar from February to March 2024 for studies that met the following criteria: (1) randomized controlled trials; (2) inclusion of eccentric-only and concentric-only strength training groups; (3) use of an isokinetic dynamometer for training and testing; (4) reporting changes over time in MVCCON and MVCECC; and (5) using healthy adult participants. The certainty of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation approach. A multilevel random-effects model meta‑analyses with robust variance estimation were performed in Rstudio software using metaphor and clubSandwich packages. Moreover, sensitivity analysis was performed, excluding the highly influential studies. The potential moderating role of sex, training status and age of the participants, muscles, velocity in training and testing, initial MVCECC, MVCCON, and MVCECC/MVCCON ratio, and training-related variables such as number of repetitions per set, number of sets, number of sessions per week, and duration of the training protocol were also assessed.
Results
Twenty-seven studies matched with the criteria, and overall 162 study results were identified and included in the meta-analyses. Greater effects on MVCECC was found after eccentric-only versus concentric-only training (Hedge’s g: 1.51; 27% vs. 10%; p < .05). However, no differences were evident between the training modalities for changes in MVCCON (Hedge’s g: − 0.10; 13% vs. 14%, p = .726) and MVCISO (Hedge’s g: − 0.04; 18% vs. 17%; p = .923). The subgroup analyses showed smaller effect of eccentric-only than concentric-only training on MVCCON when eccentric-only training was performed at higher velocities than the velocities of MVCCON testing (Hedge’s g: − 0.99; p < .05). Meta-regressions showed that the longer the training period, the greater the superior effect of eccentric over concentric training on MVCECC.
Conclusions
Eccentric-only strength training is more effective for improving MVCECC, but both concentric-only and eccentric-only training provide similar effects on improving MVCCON and MVCISO. Further studies are necessary to investigate the mechanisms underpinning the superior effect of eccentric-only training.
Background
Various muscle contraction modalities have differing effects on the musculoskeletal system. To understand the magnitude of these effects, the authors investigated the effects of eccentric and concentric contractions on the bone-tendon interface after rotator cuff repair in mice.
Hypothesis
Eccentric contraction promotes healing of the bone-tendon interface after rotator cuff repair in mice better than other muscle contraction patterns.
Study Design
Controlled laboratory study.
Methods
The authors performed acute supraspinatus tendon repair of the right shoulder in 104 C57BL/6 mice. Animals were randomized into 4 groups postoperatively: control group (Con group), horizontal running group (Horz group), +15° uphill running group (Up group), and −15° downhill running group (Down group), with 26 animals in each group. At 4 and 8 weeks postoperatively, the authors removed the eyeball, collected blood samples, and extracted the supraspinatus tendon–humerus complex for histological, immunological, bone morphological, and biomechanical tests.
Results
At 4 and 8 weeks postoperatively, the Down group exhibited a better collagen cell arrangement and fibrocartilage layer than the other 3 groups. At 4 weeks postoperatively, anti-inflammatory macrophages (M2 macrophages) were observed at the repair site in all groups except for the Con group. At 8 weeks postoperatively, M2 macrophages were withdrawn from the tendon site in all groups. The transforming growth factor β1 concentration in the Down group was greater than that in the other 3 groups at 4 weeks postoperatively, and it was higher than that in the Con group at 8 weeks postoperatively. The bone volume fraction, number of trabeculae, and thickness of trabeculae at the repair site in the Down group, as well as the ultimate strength and failure load in the biomechanical tests, were greater than those in the other 3 groups at 8 weeks postoperatively.
Conclusion
Eccentric contraction promotes healing of the bone-tendon interface after rotator cuff repair in mice better than other muscle contraction patterns.
Clinical Relevance
After clinical rotator cuff repair, patients can be rehabilitated by eccentric training to speed up the functional recovery of the shoulder joint.
Cancer cachexia causes significant declines in skeletal muscle mass and strength and is associated with a poor prognosis and impaired activities of daily living and quality of life. Therefore, treating cachexia is an important aim in physical therapy in patients with cancer. Although many studies have reported that training exercises can reduce cancer-related declines in muscle mass and strength, there is still no consensus on the most effective exercise protocol. The first part of this paper reviews the effectiveness of various exercise protocols in animal models of cancer cachexia and in patients with advanced cancer. The review includes resistance training, aerobic training, and combined training performed at least twice per week at an intensity of at least 60% of the maximal strength or heart rate. Protocols that included resistance training appeared to yield the greatest improvements in muscle strength. However, improvements in muscle mass are rarely reported, and the methods used to measure muscle mass are inconsistent. Therefore, the latter half of this paper describes clinically relevant methods for assessing muscle mass and quality. To develop the field of cancer rehabilitation, further studies should examine in detail how physical activity affects muscle mass and muscle quality, in addition to muscle strength.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.