O impacto do exercício sobre o trato gastrintestinal (TGI), apesar de pouco investigado, é uma área de grande interesse. O exercício aeróbio intenso e de longa duração pode provocar sintomas gastrintestinais. Estes podem ser divididos em sintomas superiores (vômitos, náuseas e pirose retroesternal - azia) e inferiores (diarréia, cólica abdominal, perda de apetite, sangramento, aceleração dos movimentos intestinais e vontade de defecar). A etiologia desses sintomas durante o exercício é multifatorial e inclui a redução do fluxo sanguíneo intestinal, a liberação de hormônios gastrintestinais, o estresse mecânico sobre o TGI, a desidratação, os fatores psicológicos, a idade, o sexo, a dieta e o nível de treinamento do indivíduo. Por outro lado, o exercício de baixa intensidade tem efeito protetor sobre o TGI, principalmente com relação à predisposição a certas doenças como o câncer de cólon, a diverticulite, a colelitíase e a constipação. Diversos mecanismos são postulados para explicar os efeitos do exercício sobre o TGI, contribuindo para o desenvolvimento de estratégias terapêuticas no tratamento de indivíduos com sintomas e doenças gastrintestinais.

The impact of exercise on the gastrointestinal tract (GI tract), although being little investigated, is a field of high interest. Intense endurance aerobic exercise can lead to gastrointestinal symptoms. These symptoms can be classified into upper symptoms (vomiting, nausea and retrosternal pyrosis - heartburn) and lower symptoms (diarrhea, abdominal cramps, loss of appetite, bleeding, accelerated bowel transit time, urge to defecate). These symptoms’ etiology during exercise is multifactorial and includes: reduction of intestinal blood flow, release of gastrointestinal hormones, mechanical stress on the GI tract, dehydration, psychological factors, age, gender, diet, and training status. On the other hand, low intensity exercise has a protective effect on the GI tract; mainly, with certain diseases, such as, colon cancer, diverticular disease, cholelithiases, and constipation. A variety of mechanisms have been postulated to explain the effects of exercise on the GI tract, contributing to the development of therapeutic strategies in the treatment of patients with gastrointestinal symptoms and diseases.

We investigated the effect of swimming training in rats on morphological characteristics, hypertrophy levels and metabolic and contractile adaptations of different fiber types in rat the rectus abdominis muscle. Rats were randoverly assigned to one of three groups (N = 5 each): a) swimming training for 1 h, twice a week (2x/w), b) 1 h five times a week (5x/w) for 9 consecutive weeks, or c) without any swimming training (Control). Body weight increased in 2x/w rats and decreased in the 5x/w ones. Muscle fiber diameters increased in both trained groups, with higher values in the 2x/w group. Aerobic exercise increased slow oxidative (SO) + fast-oxidative-glycolytic (FOG) fibers and decreased fast glycolytic (FG) fibers. In addition, SO fibers were increased and FOG + FG fibers were decreased in trained rats. Small and angulated atrophic fibers were also observed. These results corroborate that swimming exercise increases aerobic metabolism and thus oxidative and low contraction fibers. However, the used protocol induced, to a variable degree, changes in the muscle fiber morphology

Se estudió el efecto de la natación en las características morfológicas, niveles de hipertrofia y las adaptaciones metabólicas y contráctiles de diferentes tipos de fibras en el músculo recto del abdomen de ratas. Las ratas fueron asignadas en tres grupos (N = 5 cada uno): a) natación por 1 hora dos veces a la semana (2x/s), b) 1 hora, cinco veces por semana (5x/s) por nueve semanas consecutivas y c) sin natación (control). El peso corporal se incrementó en las ratas 2x/s y disminuyó en 5x/s. El diámetro de las fibras musculares aumentó en ambos grupos entrenados, con mayores valores en las ratas 2x/s. El ejercicio aeróbico incrementó las fibras de oxidación lenta (OL) + las fibras de glicólisis oxidativa rápida (GOR) y disminuyeron las fibras de glicólisis rápida (GR). Además, las fibras OL aumentaron y las fibras GOR y GR disminuyeron en las ratas entrenadas. Se observó una pequeña atrofia y deshidratación de las fibras. Estos resultados corroboran que la práctica de la natación incrementa el metabolismo aeróbico, las fibras de contracción lenta y la oxidación. Sin embargo, el protocolo utilizado induce cambios en grado variable en la morfología de las fibras musculares