The slope of the VO2 slow component is associated with exercise intolerance during severe-intensity exercise.

The aim of this study was to analyze the relationship between the slope of the VO2 slow component (VO2sc) and exercise tolerance (tlim) during constant-work-rate (CWR) exercise performed within the severe intensity domain. Fifteen active subjects (VO2max = 41.2 ± 5.1 ml.kg-1.min-1) performed the following tests: 1) an incremental test to determine the VO2max and the work rate associated with the VO2max (IVO2max) and; 2) two CWR transitions at 95% of the IVO2max to determine the slope of the VO2 slow component and the tlim. Three tlims were obtained: tlim1 = CWR1; tlim2 = CWR2; and tlim1+2 = (CWR1 + CWR2) / 2. There was no significant difference between the VO2max (3271.7 ± 410.7 mL·min-1) and VO2peak obtained during the CWR tests (CWR1 = 3356.3 ± 448.8 mL·min-1, CWR2 = 3362.2 ± 393.4 mL·min-1, p > 0.05). Significant correlations (p < 0.05) were found among the VO2sc kinetics and tlim1 (r = -0.53), tlim2 (r = -0.49) and tlim1+2 (r = -0.55). Thus, exercise tolerance during CWR performed within the severe intensity domain is partially explained by the slope of the VO2 slow component.