Estimation of Lactate Thresholds, Aerobic Capacity and Recovery Rate from Muscle Oxygen Saturation in Highly Trained Speed Skaters and Healthy Untrained Individuals

<b>Objective:</b> The main objective of this study was to compare lactate thresholds and aerobic capacity from a graded-intensity exercise test (GXT) for near-infrared spectroscopy measurements in healthy, untrained individuals and highly trained athletes. <b>Methods:</b> This study included 29 untrained students (13 females) and 27 highly trained speed skaters (13 females). A maximal effort GXT was performed on a cycloergometer. The lactate-based aerobic and anaerobic thresholds, and the corresponding thresholds for muscle oxygen saturation (SmO₂), were determined. <b>Results:</b> The power values determined for all thresholds were significantly higher in female and male speed skaters compared to male and female college students. SmO₂ at anaerobic thresholds was significantly lower in female speed skaters than in female students. Both female and male skaters showed greater changes in SmO₂ after the GXT compared to students. The recovery did not significantly differ between groups within gender. There was a significant positive correlation in females between the rate of muscle reoxygenation and VO₂max power (r = 0.610). In speed skaters, the rate of muscle reoxygenation was not significantly higher than students and correlated positively with VO₂max (r = 0.449). <b>Conclusions:</b> The SmO₂ at the exercise thresholds, during and after maximal exercise, depends on the training status of the individual. The participants with a higher physical fitness level showed greater decreases in ΔSmO₂ at the AT level, as well as after maximal exercise. SmO₂ corresponding to the well-established exercise thresholds may be applied to guide training prescription. The rate of muscle reoxygenation after a GXT was also dependent on the aerobic capacity of the participants.