Cardiorespiratory fitness level influences the ventilatory threshold identification

We aimed to analyze the influence of cardiorespiratory fitness (CRF) on ventilatory threshold identification (VT1) using the Ventilatory Equivalents (VEq) and V-slope methods. Twenty-two male runners (32.9 ± 9.4 years) were divided into two groups: G1 - group with less cardiorespiratory fitness (CRF: VO2max 40 to 51 ml·kg-1·min-1) and G2 - higher CRF (G1; VO2max £56,4 to 72 ml·kg-1·min-1) divided by the 50th percentile. An incremental cardiopulmonary exercise test was applied to identify VT1 using VEq and V-slope methods to compare heart rate (HR), oxygen consumption (VO2), and speed. Two-way ANOVA was used to compare HR, VO2, and speed (groups vs. methods). The Effect size was calculated using Cohen’s d. The intraclass correlation coefficient, variation coefficient, typical error, and Bland Altman were applied to verify reliability and agreement. No significant differences (p < 0.05) were found between methods for G1 (VO2, HR, and speed), and Bland Altman showed good agreement (mean difference: VO2 0.35ml·kg-1·min-1; HR 2.58bpm; speed 0.33km·h-1). However, G2 presented statistical differences between methods (VO2 and speed) and a more significant mean difference (VO2 2.68ml·kg-1·min-1; HR 6.87 bpm; speed 0.88km·h-1). The small effect size was found in G1 between methods (VO2: 0.06; speed: 0.20; HR: 0.14), and small and moderate effects were found in G2 between methods (VO2: 0.39; speed: 0.43; HR: 0.51). In conclusion, runners with lower CRF have a better agreement for the V-slope and VEq methods than those with a higher CRF.