Abstract des Autors

The EMG signal is a reflection of the amplitude and frequency of the myoelectric activity. It can therefore be used to represent the evolution of fatigue during a given exercise. The literature states that the amplitude increases and that the frequency of the EMG decreases with fatigue during submaximal exercise. Electromyographic modifications induced by fatigue are subject of many studies. These studies dealt with the acute responses of the muscle groups during isometric anbd dynamic exercise. Objective of this study was to examine effects of training on the evolution of changes in the myoelectric signal during fatiguing dynamic contractions. 13 subjects (6 girls, 7 boys) executed flexion/extension of the elbow at a work load of 20 of the IRM (extension) until exhaustion. The myoelectric activity of the triceps brachii was recorded before and after 6 wk of training. Statistical analyses indicated an improved duration of exercise of 177 but no change in maximal force. Fatigue induced an increase in maximal amplitude (65) and mean amplitude (75) of EMG bursts. These changes were seen before and after training. Median frequency (MF) of the surface EMG power spectrum diminished during fatigue before training, but did not change after training. Results demonstrate that training of triceps brachii increases its capacity to maintain dynamic exercise for a prolonged period with the same motor units. An interesting finding was that training changed the evolution of the EMG during fatigue in slowing down the rate of changes. Verf.-Referat