The influence of muscle fiber type on slow component of oxygen uptake kinetics

Abstract

The purpose of this study was to investigate the influence of muscle fiber type on the slow component of oxygen uptake (VO2) kinetics and electromyographic activity. Twelve sprinters and ten endurance runners participated in the study. They performed two separate treadmill running tests, the first test being conducted to determine the ventilatory threshold and maximal oxygen uptake. The second test consisted of a 6 min running bout at severe exercise intensity. A two-component exponential model was used to fit the VO2 response. Surface electromyographic signals were collected from Vastus lateralis, and processed by wavelet analysis. Sprinters and endurance runners, with their distinct anaerobic and aerobic fitness, showed a substantial difference in VO2 slow component during severe exercise. The sprinters showed a significantly higher VO2 slow component amplitude (A2: 381.0 ± 96.3 mL/min) and a significantly earlier slow component onset (TD2: 118.1 ± 16.1 s) than the endurance runners (A2: 142.2 ± 58.4 mL/min, TD2: 145.9 ± 19.9 s). The electromyographic mean power frequency of the tested muscles increased significantly during the slow component phase. There is a significant correlation between VO2 slow component and electromyographic mean power frequency for endurance runners ( r = 0.50, p = 0.003). The combined use of VO2 kinetics modeling and electromyographic measurement provides evidence of the influence of muscle fiber type on slow component of oxygen uptake kinetics during severe intensity exercise.