Effects of eccentric exercise on muscle architecture in adults: a systematic review / Efectos del ejercicio excéntrico en la arquitectura muscular en adultos: una revisión sistemática

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.

RESUMEN: El propósito de esta revisión sistemática fue determinar los efectos del entrenamiento excéntrico sobre la arquitectura muscular en la población adulta. Se siguieron las recomendaciones del Ìtems de referencia para publicar Revisiones Sistemáticas y Metaanálisis (PRISMA) utilizando palabras clave asociadas con la arquitectura muscular y el entrenamiento excéntrico en cuatro bases de datos: PubMed, Scopus, SPORTDiscus y Web of Science. La calidad metodológica se evaluó mediante la escala PEDro. Se encontró un total de 1260 artículos, del los cuales, 18 fueron incluidos en esta revisión. Los parámetros más frecuentemente evaluados en los estudios fueron el ángulo de penación (AP), la longitud del fascículo (LF) y el grosor muscular (Gm). Estos fueron evaluados principalmente en músculos de los miembros inferiores como la cabeza larga del bíceps femoral (CLBf), el vasto lateral (VL), el gastrocnemio medial (GM) y el gastrocnemio lateral (GL), respectivamente. El entrenamiento excéntrico durante al menos cuatro semanas genera adaptaciones en estos parámetros, principalmente aumentando el GM con la LF y disminuyendo el AP, determinando de esta manera la función muscular. Estos resultados aportan evidencias sobre los efectos del entrenamiento excéntrico en la arquitectura muscular, que podrían ser útiles para prevenir lesiones y favorecer los procesos de recuperación muscular.

Effect of eccentric training on mitochondrial function and oxidative stress in the skeletal muscle of rats

The objective of the present study was to investigate the effects of eccentric training on the activity of mitochondrial respiratory chain enzymes, oxidative stress, muscle damage, and inflammation of skeletal muscle. Eighteen male mice (CF1) weighing 30-35 g were randomly divided into 3 groups (N = 6): untrained, trained eccentric running (16°; TER), and trained running (0°) (TR), and were submitted to an 8-week training program. TER increased muscle oxidative capacity (succinate dehydrogenase and complexes I and II) in a manner similar to TR, and TER did not decrease oxidative damage (xylenol and creatine phosphate) but increased antioxidant enzyme activity (superoxide dismutase and catalase) similar to TR. Muscle damage (creatine kinase) and inflammation (myeloperoxidase) were not reduced by TER. In conclusion, we suggest that TER improves mitochondrial function but does not reduce oxidative stress, muscle damage, or inflammation induced by eccentric contractions.

Treinamento de força excêntrico em idosos: revisão acerca das adaptações fisiológicas agudas e crônicas / Eccentric resistance training in elderly: review on the acute and chronic physiological adaptations

Já está bem estabelecido na literatura que a manutenção da massa muscular tem um importante papel na capacidade funcional, manutenção da saúde e independência dos idosos. Deste modo, o estudo dos mecanismos envolvidos com o processo fisiológico no envelhecimento tem sido evidenciado nas ultimas três décadas, fato que impulsionou os interesses sobre as relações do exercício físico com a melhoria da qualidade de vida e saúde da população idosa. Ademais, considerando o declínio das funções fisiológicas do músculo humano e outros sistemas com o avanço da idade, o treinamento de força pode ser aplicado como ferramenta preventiva aos processos degenerativos associados ao envelhecimento. Dentre as diferentes formas de contração músculo-esquelética, o treinamento que visa priorizar a ação excêntrica recebeu considerável atenção. Neste sentido, o presente estudo teve como objetivo apresentar os efeitos agudos e crônicos do treinamento de força excêntrico sobre as respostas cardiorrespiratórias, metabólicas e neuromotoras em idosos. Foi realizada uma busca bibliográfica utilizando os seguintes unitermos: resistance training, molecular mechanisms, hypertrophy, eccentric resistance training e aging, nas bases de dados PubMed, MEDLINE, SciELO e LILACS. A presente revisão indica que os exercícios que priorizam as ações excêntricas promovem menor sobrecarga cardiorrespiratória, metabólica e neuromotora quando comparados com exercícios de ação concêntrica e isométrica. Por esta razão, o treinamento de força excêntrico torna-se potencialmente adequado para idosos, os quais possuem uma relativa preservação da força excêntrica durante o envelhecimento, bem como risco e/ou doenças cardiorrespiratórias e neuromotoras. Adicionalmente, este tipo de treinamento induz ao ganho de massa muscular e capacidade funcional em idosos.

It is well established in the literature that muscle mass maintenance has an important role on functional capacity, health maintenance and independence in elderly. Thus, the study of the mechanisms involved with the physiological process of aging have been evidenced in the last three decades, which has stimulated the interests on the relationships of exercise with the improvement of life quality and health of the elderly population. Apart from this, considering the decrease of the physiological function of the human muscle and other systems with aging, resistance training can be prescribed as preventive tool to the degenerative process associated with aging. Between the different forms of skeletal-muscle contraction, the training targeting eccentric actions has received considerable attention. In this sense, the present study had the objective to present the acute and chronic effects of eccentric resistance training on cardiorespiratory, metabolic and neuromotor responses in elderly. A bibliographic search using the following keywords was done: resistance training, molecular mechanisms, hypertrophy, eccentric resistance training and aging, on the databases PubMed, MEDLINE, SciELO and LILACS. The present review indicates that exercises targeting eccentric actions promote lower cardiorespiratory, metabolic, and neuromotor stress as compared with exercises of concentric and isometric muscle actions. For this reason, eccentric resistance training becomes potentially adequate for elderly, which have relative reservation of eccentric force during aging, as well as risk for and/or cardiorespiratory and neuromotor diseases. Additionally, this type of training induces gains of muscle mass and functional capacity in elderly.

The effects of knee extensor eccentric training on functional tests in healthy subjects / Os efeitos do treino isocinético excêntrico dos extensores do joelho nos testes funcionais em sujeitos saudáveis

BACKGROUND: It is well known that eccentric training increases muscle strength and promotes greater neural activation, and therefore has been used in the recovery of knee extensors. The hypothesis of this study was that there would be a strong correlation between knee extensor torque and functional tests. OBJECTIVES: To investigate the relationship between knee extensor peak torque and functional tests of agility (runs) and propulsion (hop for distance) after short-term isokinetic eccentric training. METHODS: Twenty healthy and active male undergraduate students (age 22.5±2.1 years; height 1.72±0.10 m; weight 67.8±9.5 kg; body mass index: 22.5±2.0 kg/m²), with no abnormalities or history of injury of the limbs, performed an isokinetic assessment of the knee extensors and flexors and also functional tests before and after isokinetic training, which consisted of 3 sets of 10 MVECs at 30º/s, with 3 minutes of rest between sets, twice a week for 6 weeks. RESULTS: The eccentric training increased the extensor peak torque (16, 27 and 17 percent; P<0.01) and decreased the H/Q ratio (10, 20 and 13 percent; P<0.01) for the isometric and eccentric modes at 30°/s and 120°/s, respectively. It also decreased the time in two of the five agility tests (carioca and pivot diagonal; P<0.01), and increased the distance in the hop tests, for both dominant and non-dominant limbs (P<0.01). CONCLUSIONS: Although the eccentric training led to an increase in extensor peak torques as well as an improvement in most of the functional tests, the hypothesis that a strong correlation would be observed between peak torques and functional tests was not confirmed. Article registered in the Australian New Zealand Clinical Trials Registry (ANZCTR) under the number 12607000590460.

CONTEXTUALIZAÇÃO: Sabe-se que o treino excêntrico aumenta a força muscular, promovendo uma maior ativação neural e, portanto, tem sido usado na recuperação do torque extensor. A hipótese deste estudo foi a de que possa existir uma forte correlação entre o torque extensor do joelho e os testes funcionais. OBJETIVOS: Correlacionar o torque extensor do joelho com os testes funcionais de agilidade (corridas) e impulsão (saltos em distância) após o treino isocinético excêntrico de curta duração. MÉTODOS: Vinte homens universitários, ativos e saudáveis (22,5±2,1 anos; 1,72±0,10 m; 67,8±9,5 kg; IMC 22,5±2,0 kg/m²), sem reportar anormalidades ou história de lesão no membro inferior, realizaram avaliação isocinética do torque extensor e flexor do joelho e testes funcionais antes e depois do treino isocinético que consistiu em três séries de 10 CEVM a 30º/s, com 3 minutos de repouso entre as séries, realizado duas vezes por semana, durante seis semanas. RESULTADOS: O torque extensor aumentou (16, 27 e 17 por cento; P<0,01), a razão I/Q diminuiu (10, 20 e 13 por cento; p<0,01) para os modos: isométrico e excêntrico a 30°/s e 120°/s, respectivamente; diminuiu o tempo em dois dos cinco testes de corridas (carioca e pivô diagonal; P<0,01) e aumentou a distância nos testes de saltos tanto para o membro dominante quanto para o não dominante (P<0,01). CONCLUSÕES: Embora o treino excêntrico tenha aumentado o torque dos extensores do joelho, bem como melhorado a maioria dos testes funcionais, a hipótese de uma forte correlação entre essas variáveis não se confirmou. Artigo registrado no Australian New Zealand Clinical Trials Registry (ANZCTR) sob o número 12607000590460.

Peak torque and knee kinematics during gait after eccentric isokinetic training of quadriceps in healthy subjects / O pico de torque e a cinemática do joelho durante a marcha após treino isocinético excêntrico do quadríceps em sujeitos saudáveis

OBJECTIVE: To evaluate the effects of eccentric isokinetic training on knee range of motion (ROM) of healthy subjects. METHODS: The knee extensor and flexor isokinetic peak torques and ROM of flexion/extension and varus/valgus knee movements during gait of 18 healthy men (21.7±2.2 years; 1.73±0.10m; 68.7±9.4kg; body mass index: 22.6±2kg/m²) were analyzed, before and after six weeks of bilateral eccentric isokinetic training of the knee extensors at 30º/s. RESULTS: The knee extensor torque increased in both limbs (right, from 229±54 to 304±53Nm; p<0.01; and left, from 228±59 to 311±63Nm; p<0.01), without any difference in torque gain between them. The knee flexor peak torque increased (from 114±30 to 123±22Nm; p<0.05), but the hamstrings/quadriceps (H/Q) ratio decreased (from 0.5±0.08 to 0.39±0.07; p<0.01) after the training. There were no differences in the flexion/extension and varus/valgus movements after the training, except for a small change (4°) in valgus for the left knee. CONCLUSIONS: The eccentric isokinetic training of the knee extensors increased the extensor torque and decreased the H/Q ratio, although the effect on the gait pattern seemed negligible in healthy subjects. Associated training for flexors, complementary to the extensor training, seems to be necessary for balance between knee agonists and antagonists.

OBJETIVO: Avaliar os efeitos do treino isocinético excêntrico sobre a amplitude de movimento (ADM) do joelho em sujeitos saudáveis. MÉTODOS: Foram analisados os picos de torque isocinético dos extensores e flexores do joelho e a ADM de flexo/extensão e valgo/varo, durante a marcha, de 18 homens saudáveis (21,7±2,2 anos; 1,73±0,10m; 68,7±9,4kg; índice de massa corpórea: 22,6±2kg/m²) antes e após seis semanas de treino isocinético excêntrico bilateral dos extensores do joelho a 30º/s. RESULTADOS: O torque extensor do joelho aumentou em ambos os membros, direito (de 229±54 para 304±53Nm; p<0,01) e esquerdo (de 228±59 para 311±63Nm; p<0,01) sem diferença de ganho de torque entre eles. O pico de torque flexor aumentou (de 114±30 para 123±22Nm; p<0,05), mas a razão isquiotibiais/quadríceps (I/Q) diminuiu (de 0,5±0,08 para 0,39±0,07; p<0,01) após o treino. Não houve diferença para os movimentos de flexo/extensão e valgo/varo após o treino, exceto uma pequena mudança (4°) no valgo para o joelho esquerdo. CONCLUSÕES: O treino isocinético excêntrico dos extensores do joelho aumentou o torque extensor e diminuiu a razão I/Q, entretanto o efeito sobre o padrão da marcha parece desprezível em sujeitos saudáveis. Um treino associado dos flexores, complementar ao treino dos extensores parece ser necessário para o equilíbrio entre agonistas e antagonistas do joelho.