Correlation of gas exchange threshold and first muscle oxyhemoglobin inflection point with time-to-exhaustion during heavy-intensity exercise.

The twofold aim of the study was to: 1) compare the gas exchange threshold (GET), the first oxyhemoglobin inflection point ([O2Hb]-T), and perceptual threshold as determined during an incremental exercise test, and 2) investigate the link between each threshold and time-to-exhaustion during heavy intensity exercise.Fourteen competitive cyclists performed an incremental exercise test to exhaustion on a cycloergometer to determine the different thresholds and peak workload (Wpeak). The participants then performed a sub-maximal constant workload test (90% Wpeak) to exhaustion to determine time-to-exhaustion. The thresholds were identified from: 1) the first breakpoint in the oxygen uptake vs. carbon dioxide output curve (GET), 2) the [O2Hb]-T, and 3) a rating of 13 in perceived exertion (perceptual threshold: RPE13-T).Oxygen uptake at the different thresholds was not significantly different (P>0.05). Moreover, GET and [O2Hb]-T were significantly correlated: 1) to each other (r≥0.79; P≤0.001), and 2) to time-to-exhaustion (r=0.81 and r=0.72, respectively; P<0.01). RPE13-T, however, was not significantly correlated with the time-to-exhaustion (P=0.148).The anaerobic threshold as identified from GET was concomitant to [O2Hb]-T. Both thresholds were correlated to time-to-exhaustion, and could therefore be used as a performance index in middle-duration events.