Analise do torque isometrico e da atividade elétrica apos lesão muscular induzida por exercício excentrico em humanos / Analysis of isometrci torque and of the electrical activity after induced muscle damage by eccentric exercise human

Este estudo avaliou e relacionou as alteracoes funcionais domusculo quadriceps femoral apos lesao induzida pelo exercicio excentrico. O torque isometrico maximo medio desse musculo e a eletromiografia de superficie (raiz quadrada da media dos quadrados, root meam square - RMS; frequencia mediana -FM) dos musculos vasto medial obliquo(VMO) e vasto lateral(VL) foram avaliados antes, imediatamente apos e durante os 7 dias apos o exercicio excentrico. As imagens de ressonancia magnetica nuclearRMN) de tres voluntarias foram usadas para evidenciar a presenca de lesao muscular. Nove mulheres (21,7+-1,48 anos), sedentarias e saudaveis, foram avaliadas. A lesao foi induzida por meio de contracoes isocineticas excentricas. O torque isometrico maximo medio e a atividade eletrica foram mensurados por meio da contracao isometrica maxima com o joelho a 90 graus de flexao. O torque isometrico maximo medio diminiu imediatamente apos o exercicio excentrico (p<0,01), com recuperacao gradual na primeira semana. O RMS do musculo VL diminuiu imediatamente apos o exercicio excentrico (p<0,05). Por outro lado, somente o musculo VMO ocorreu aumento na FM imediatamente apos o exercicio excentrico (p<0,01). Correlacao significativa foi observada entre o torque isometrico maximo medio e a FM do musculo VMO entre o 1o. e 7o. dia apos o exercicio (r=0,32, p<0,05). Extensas areas de lesao no musculo quadriceps femoral foram identificadas pela RMN. Em conclusao, o exercicio excentrico diminuiu o torque isometrico maximo medio e alterou o sinal eletromiografico, os quais se recuperaram gradualmente na primeira semana, apesar da presenca de lesao muscular

Functional changes of human quadriceps muscle injured by eccentric exercise

The present study evaluated functional changes of quadriceps muscle after injury induced by eccentric exercise. Maximal isometric torque of quadriceps and the surface electromyography (root mean square, RMS, and median frequency, MDF) of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles were examined before, immediately after and during the first 7 days after injury. Serum creatine kinase (CK) levels and magnetic resonance imaging (MRI) were used to identify muscle injury. The subject was used as her own control and percent refers to pre-injury data. Experiments were carried out with a sedentary 23-year-old female. Injury was induced by 4 bouts of 15 maximal isokinetic eccentric contractions (angular velocity of 5º/s; range of motion from 40º to 110º of knee flexion). The isometric torque of the quadriceps (knee at 90º flexion) decreased 52 percent immediately after eccentric exercise and recovered on the 5th day. The highest reduction of RMS occurred on the 2nd day after injury in both VL (63 percent) and VMO (66 percent) and only VL recovered to the pre-injury level on the 7th day. Immediately after injury, the MDF decreased by 5 and 3 percent (VMO and VL, respectively) and recovered one day later. Serum CK levels increased by 109 percent on the 2nd day and were still increased by 32 percent on the 7th day. MRI showed large areas of injury especially in the deep region of quadriceps. In conclusion, eccentric exercise decreased the isometric torque and electromyographic signals of quadriceps muscle, which were recovered in one week, despite the muscle regeneration signals