THE SLOW COMPONENT OF OXYGEN UPTAKE AND THE MEAN POWER FREQUENCY OF EMG DURING HEAW INTENSITY EXERCISE

##article.abstract##

The purpose of this study was to elucidate the mechanisms causing the slow component of oxygen uptake (VO2), by investigating changes in exercising muscle electrical activity. Volunteers performed square-wave dynamic knee extension exercise. Surface EMG of the rectus femoris was used to measure mean power frequency (MPF) and integrated (IEMG) values for each contraction. VO2 was measured breath-by-breath using a mass spectrometer. During 'heavy' intensity exercise eliciting a VO2 slow component and muscle fatigue, there was no decrease in MPF, which contrasts with 'severe' exercise where the MPF decreased as muscle fatigue occurred. Results from this study suggest a change in fibre recruitment from slow-twitch to oxygen-inefficient high-frequency fasttwitch fibres during fatiguing exercise as the cause of the VO2 slow component.