Efeitos do treino em plataforma vibratória nos parâmetros histomorfométricos do músculo extensor longo dos dedos de ratos wistar obesos – MSG

Abstract

Obesity causes morphological changes in musculoskeletal tissue and, in order to prevent them, it is recommended the practice of physical exercise. The vibration platform is an exercise method that has been used because, by means of oscillatory vibrations, it stimulates muscle contractions that can improve power, strength, and muscle trophism, besides promoting energy expenditure, which improves the energy balance. The aim of this research was to verify the effects of the vibration platform on the extensor digitorum longus muscle of Wistar rats with MSG (monosodium glutamate)-induced obesity. The sample consisted of 24 Wistar rats, neonates, randomly divided into 2 groups: CG (Control Group) and GO (MSG Group). From the 1st to the 5th day of life, they were submitted to daily intradermal injections; the GO received monosodium glutamate, at a dose of 4 mg/g body weight, with the objective of promoting obesity and the CG, hyperosmotic saline solution 1.25 mg/g body weight, simulating the same stress. At 70 days, we began training on vibration platform; for this, the groups were subdivided into CPG (control group + vibration platform) and GOP (group MSG + vibration platform), with 6 animals in each group. The training protocol had frequency adjusted to 60 Hz and amplitude of 2 millimeters; the action was performed three times a week for ten minutes over a period of eight consecutive weeks. At 130 days of age, all animals had their body weight and nasoanal length measured to verify the incidence of obesity by analyzing the Lee Index, which proved the incidence of obesity, but showed no statistically significant difference when compared to control groups. The animals were euthanized, and the extensor digitorum longus (EDL) muscle of both antimersals was collected for histological processing for morphological and histomorphometric analyses of the cross-sectional area, the largest and smallest diameter, and density of the muscle fibers, as well as the neuromuscular junctions. The data obtained were expressed using descriptive statistics (mean and standard error) and analyzed with SPSS 20.0 software. Generalized Linear Models (Normal or Gamma probability distribution) were used, with LSD post-test, always with a 5% significance level. The morphological analysis of the EDL of MSG animals exhibited muscle hypotrophy, amorphous fibers with dye differences, increased number of nuclei, higher density of muscle fibers and higher amount of type II fibers. Regarding cross-sectional area, density, largest and smallest muscle fiber diameter, as well as muscle fiber types, the MSG groups of animals exhibited muscle hypotrophy, with higher density of muscle fibers, as well as a greater amount of type IIb fibers. However, there was no difference in the areas of neuromuscular junctions of the platform groups. It was possible to conclude that the proposed obesity model, as well as the vibration platform training were able to cause morphological changes in the EDL of Wistar rats, and further studies are needed to confirm such findings.