BackgroundCompared to eccentric contractions, concentric contractions result in higher cardiovascular stress. However, we do not know how these two types of contractions influence cardiac autonomic modulation during the post-exercise recovery period.Objectiveto compare the effect of resistance training that is performed with concentric vs. eccentric emphasis on muscle strength and on post-exercise recovery which was assessed by examining heart rate variability (HRV), for the knee extensor muscle group in young healthy adults.MethodsFor this study, 105 men between 18 and 30 years of age were randomized into 4 groups: concentric control (CONCC), eccentric control (ECCC), concentric training (CONCT) and eccentric training (ECCT). The CONCC and ECCC groups underwent one session of resistance exercise (RE) using the knee extensor muscle group (3 sets of 1 repetition at 100% of the maximal repetition [1MR]) and the CONCT and ECCT groups performed 10 training sessions. The HRV was analyzed at baseline and across four recovery periods (T1, T2, T3 and T4). ResultsThe ECCT group exhibited increased muscle strength at the end of the study. Regarding cardiac autonomic modulation, the CONCC and ECCC groups exhibited increases in overall variability (SDNN and SD2) at T1 compared to baseline, and the ECCT group demonstrated increases in variables reflecting vagal modulation and the recovery process (RMSSD, SD1 and HF [ms2]) at T1, T2 and T4 compared to baseline. ConclusionsResistance training with emphasis on eccentric contractions promoted strength gain and an increase in cardiac vagal modulation during recovery compared to baseline.
Objective: To evaluate the effect of exposure to cigarette smoke and running training on a treadmill on the expression of glucose transporter GLUT4 in oxidative soleus muscle of rats. Materials and methods: Wistar rats were divided into: (C) control, (E) exercise control, (SS), sedentary smoker, and (ES) exercise smoker. Insulin Tolerance Test, Western blotting, and RT--PCR were performed for the evaluation of GLUT4 levels. Results: The SS group presented lower insulin sensitivity with reduced GLUT4 protein in the plasma membrane (PM), no changes in the microsomal fraction, but increased mRNA content. Training reversed this condition. No intervention altered total GLUT4 content of the oxidative muscle. Conclusion: These results suggest that passive smoking stimulates GLUT4 transcription without changing total protein content, but impairs the ability of GLUT4 translocation to the PM. On the other hand, training seems to reduce the deleterious effects, even under the influence of cigarette smoking. Arq Bras Endocrinol Metab. 2013;57(1):19-26 Keywords Cigarette smoking; training; glucose transporter; GLUT4; insulin resistance; oxidative muscle RESUMO Objective: Avaliar o efeito da exposição à fumaça de cigarro e do treinamento de corrida em esteira rolante sobre a expressão do transportador de glicose GLUT4 no músculo oxidativo solear de ratos. Materiais e métodos: Ratos Wistar foram divididos em: (C) controle, (E) exercitado, (SS) fumante sedentário e (ES) fumante exercitado. Foram realizados testes de tolerância à insulina, Western Blotting e RT-PCR para avaliação da expressão de GLUT4. Resultados: O grupo SS apresentou menor sensibilidade à insulina, com redução de proteína GLUT4 na membrana plasmática (MP), sem alteração na fração microssomal, e conteúdo de RNAm aumentado. O treinamento reverteu esse quadro. Nenhuma intervenção alterou o conteúdo total de GLUT4 no músculo oxidativo. Conclusão: Esses resultados sugerem que o fumo estimula a transcrição de GLUT4 sem alterar o conteúdo total de proteína, porém prejudica a capacidade de translocação para a MP. Já o treinamento em esteira parece, mesmo sob influência do cigarro, reduzir seus efeitos deletérios. Arq Bras Endocrinol Metab. 2013;57(1):19-26 Descritores
BackgroundLocalized exercises are widely used in rehabilitation processes. The predominant options are exercises with an emphasis on either concentric or eccentric contractions. Eccentric exercises promote greater strength gains compared to classical concentric stimuli, but can cause muscle damage. The aim of present study was to compare strength training composed of 10 sessions with progressive loads between groups with a predominance of concentric versus eccentric contraction through an analysis of isotonic strength, pressure pain threshold, creatine kinase, tumor necrosis factor-alpha and cortisol.MethodsOne hundred twenty male subjects were divided into four groups: C1 and E1 – single session of maximum strength with emphasis on concentric and eccentric contraction, respectively; C10 and E10 – 10 sessions with progressive loads from 80% to maximum strength with emphasis on concentric and eccentric contraction, respectively.ResultsIsotonic strength increased by 10% in E10 following the ten training sessions. C1 and E1 exhibited a lower pressure pain threshold 48 hours after the sessions in comparison to C10 and E10, respectively. Creatine kinase was increased in C1 in comparison to baseline, with significant differences (p ≤ 0.05) in comparison to E1 at 48 and 96 hours as well as C10 at 48, 72 and 96 hours. No significant differences were found in TNF-α or cortisol among the groups or evaluation times.ConclusionEccentric contraction training promotes functional adaptation. Moreover, both concentric and eccentric contraction training have a protective effect on the muscle in relation to a single session of maximum strength exercise.Trial registrationRBR-75scwh
INTRODUÇÃO E OBJETIVO: Sabe-se que o tabagismo pode provocar alterações cardiovasculares e redução na sensibilidade à insulina, e que o exercício físico melhora este quadro. O objetivo do estudo foi avaliar o efeito do tabagismo e da prática de atividade física sobre a sensibilidade à insulina em músculo cardíaco de ratos, através da avaliação de expressão do transportador de glicose GLUT4. MÉTODOS: Ratos machos Wistar foram divididos em quatro grupos: (CS) controle, (CE) controle exercitado, (FS) fumante sedentário e (FE) fumante submetido ao exercício físico. Os grupos FS e FE foram submetidos à combustão de quatro cigarros/30 min/60 dias, 2x/dia. Os grupos CE e FE executaram corrida em esteira rolante durante 60 min/60 dias. Foi realizado teste de tolerância à insulina, e a expressão de GLUT4 no coração foi feita através de Western Blotting - ECL e RT-PCR. Foi utilizado método estatístico descritivo e o teste ANOVA, e as diferenças entre os grupos foram consideradas significantes quando P < 0,05. RESULTADOS: Nem o tabagismo nem a atividade física alteraram o peso corpóreo (CS: 364,7 ± 9,7; CE: 372,4 ± 7,2, FS: 368,9 ± 6,7; FE: 376,4 ± 7,8g) e o peso do coração (CS: 1,12 ± 0,05; CE: 1,16 ± 0,04; FS: 1,14 ± 0,05; FE: 1,19 ± 0,05g). A sensibilidade à insulina foi reduzida no grupo fumante, porém, a prática de exercício físico melhorou este quadro (CS: 3,7 ± 0,3; CE: 5,28 ± 0,5*; FS: 2,1 ± 0,7*; FE: 4,8 ± 0,09** %/min; *P < 0,05 vs. CS, **P < 0,05 vs. FS). Os conteúdos de RNAm e de proteína não se alteraram entre os grupos. Porém, quando se calculou o conteúdo total de proteína GLUT4 por grama de tecido, observou-se que o tabagismo causou redução e que o exercício induziu aumento neste parâmetro (CS: 119,72 ± 9,98; CE: 143,09 ± 9,09; FS: 84,36 ± 10,99*; FE: 132,18 ± 11,40# UA/g tecido, *P < 0,05 vs. CS, #P < 0,01 vs. FS). CONCLUSÃO: Conclui-se que o tabagismo reduz a sensibilidade à insulina e a capacidade do coração captar glicose. Já a prática de exercício físico moderado reverte este quadro por completo.
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