Brain serotonin and dopamine are neurotransmitters related to fatigue, a feeling that leads to reduced intensity or interruption of physical exercises, thereby regulating performance. The present review aims to present advances on the understanding of fatigue, which has recently been proposed as a defense mechanism instead of a “physiological failure” in the context of prolonged (aerobic) exercises. We also present recent advances on the association between serotonin, dopamine and fatigue. Experiments with rodents, which allow direct manipulation of brain serotonin and dopamine during exercise, clearly indicate that increased serotoninergic activity reduces performance, while increased dopaminergic activity is associated with increased performance. Nevertheless, experiments with humans, particularly those involving nutritional supplementation or pharmacological manipulations, have yielded conflicting results on the relationship between serotonin, dopamine and fatigue. The only clear and reproducible effect observed in humans is increased performance in hot environments after treatment with inhibitors of dopamine reuptake. Because the serotonergic and dopaminergic systems interact with each other, the serotonin-to-dopamine ratio seems to be more relevant for determining fatigue than analyzing or manipulating only one of the two transmitters. Finally, physical training protocols induce neuroplasticity, thus modulating the action of these neurotransmitters in order to improve physical performance.
The study evaluates whether the intrinsic capacity for physical exercise influences dopamine neuroplasticity induced by physical training. Male rats were submitted to three progressive tests until fatigue. Based on the maximal time of exercise (TE), rats were considered as low performance (LP), standard performance (SP) or high performance (HP) to exercise. Eight animals from each group (LP, SP, and HP) were randomly subdivided in sedentary (SED) or trained (TR). Physical training was performed for 6 wk. After that, concentrations of dopamine (DA), serotonin (5-HT), and their metabolites and mRNA levels of D1 receptor ( Drd1), D2 receptor ( Drd2), dopamine transporter ( Dat), tyrosine hydroxylase ( Th), glia cell line neurotrophic factor ( Gdnf), and brain-derived neurotrophic factor ( Bdnf) were determined in the caudate-putamen (CPu). TE was increased with training in all performance groups. However, the relative increase was markedly higher in LP rats, and this was associated with a training-induced increase in dopaminergic activity in the CPu, which was determined by the 3,4-dihydroxyphenylacetic acid (DOPAC)/DA ratio. An opposite monoamine response was found in HP-TR rats, in which physical training decreased the DOPAC/DA ratio in the CPu. Moreover, LP-SED rats displayed higher levels of Drd2 in the CPu compared with the other SED groups, and this higher expression was decreased by physical training. Physical training also decreased Dat and increased Gdnf in the CPu of LP rats. Physical training decreased Bdnf in the CPu only in HP rats. Thus, we provide evidence that the intrinsic capacity to exercise affects the neuroplasticity of the dopaminergic system in response to physical training. NEW & NOTEWORTHY The findings reported reveal that dopaminergic neuroplasticity in caudate-putamen induced by physical training is influenced by the intrinsic capacity to exercise in rats. To evaluate the dopaminergic neuroplasticity, we analyzed mRNA levels of D1 receptor, D2 receptor, dopamine transporter, tyrosine hydroxylase, glia cell line neurotrophic factor, and brain-derived neurotrophic factor as well as concentrations of dopamine, serotonin, and their metabolites. These results expand our knowledge about the interrelationship between genetic background, physical training, and dopaminergic neuroplasticity.
The present study investigated whether intrinsic exercise capacity affects the changes in thermoregulation, metabolism and central dopamine (DA) induced by treadmill running. Male Wistar rats were subjected to three incremental exercises and ranked as low-performance (LP), standard-performance (SP) and high-performance (HP) rats. In the first experiment, abdominal (T) and tail (T) temperatures were registered in these rats during submaximal exercise (SE) at 60% of maximal speed. Immediately after SE, rats were euthanized and concentrations of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) were determined in the preoptic area (POA). In the second experiment, oxygen consumption (VO) was measured and mechanical efficiency (ME) was calculated in these rats during an incremental exercise. HP rats ran for longer periods and fatigued with higher T values, with no difference in T. Nevertheless, thermoregulatory efficiency was higher in HP rats, compared to other groups. DA and DOPAC concentrations in the POA were increased by SE, with higher levels in HP compared to LP and SP rats. VO also differed between groups, with HP rats displaying a lower consumption throughout the incremental exercise but a higher VO at fatigue. ME, in turn, was consistently higher in HP than in LP and SP rats. Thus, our results show that HP rats have greater T values at fatigue, which seem to be related to a higher dopaminergic activity in the POA. Moreover, HP rats exhibited a greater thermoregulatory efficiency during exercise, which that can be attributed to a lower VO, but not to changes in tail heat loss mechanisms.
Efeitos do treinamento resistido associado à oclusão vascular em lesões osteomusculares de membros inferiores: revisão da literatura Effects of resisted training associated with vascular occlusion in osteomuscular injuries of lower members: literature review
As lesões osteosmusculares de membros inferiores trazem várias limitações aos indivíduos, além de alterações que atrasam o processo de reabilitação como dor, edema, fraqueza e atrofia. Essas alterações impactam negativamente a capacidade muscular e impossibilitam que sejam aplicados programas de fortalecimento com cargas elevadas, atrasando a reabilitação. A realização do exercício resistido associado à oclusão vascular (TR-OV), mais conhecido como método KAATSU, tem por objetivo proporcionar aos indivíduos que não toleram exercícios com cargas elevadas, ganhos de força e hipertrofia muscular de forma acelerada. OBJETIVO: Verificar os efeitos do exercício resistido associado à oclusão vascular na reabilitação de lesões osteomusculares em membros inferiores. MÉTODOS: Foram selecionados artigos das bases de dados SciELO, PubMed e PEDro utilizando as palavras chaves: "vascular occlusion", "physiotherapy", "resistence exercise", "reabilitação", "oclusão vascular", "restrição do fluxo sanguíneo", "fisioterapia", "exercício resistido". RESULTADOS E DISCUSSÃO: Foram encontrados nove estudos. Os principais resultados observados com TR-OV foram: melhora na dor e qualidade de vida dos indivíduos avaliados, aumento na resposta hipertrófica e força. Os resultados revelaram efeitos melhores com TR-OV em comparação com a reabilitação convencional, exercícios com resistência de baixa e alta carga. Também foi observado melhora na função durante os exercícios no grupo TR-OV quando comparado aos demais grupos. CONCLUSÃO: A reabilitação de lesões musculoesqueléticas em membros inferiores pode ser otimizada pela técnica de TR-OV e ter resultados semelhantes aos exercícios com altas cargas. Ressalta-se que o TR-OV gera resultados positivos na reabilitação em amplos aspectos como na diminuição da dor, aumento da força e massa muscular.
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