Is the Ventilatory Efficiency in Endurance Athletes Different?-Findings from the NOODLE Study.

Background: Ventilatory efficiency (VE/VCO 2 ) is a strong predictor of cardiovascular diseases and defines individuals' responses to exercise. Its characteristics among endurance athletes (EA) remain understudied. In a cohort of EA, we aimed to (1) investigate the relationship between different methods of calculation of VE/VCO 2 and (2) externally validate prediction equations for VE/VCO 2 . Methods: In total, 140 EA (55% males; age = 22.7 ± 4.6 yrs; BMI = 22.6 ± 1.7 kg·m -2 ; peak oxygen uptake = 3.86 ± 0.82 L·min -1 ) underwent an effort-limited cycling cardiopulmonary exercise test. VE/VCO 2 was first calculated to ventilatory threshold (VE/VCO 2 -slope), as the lowest 30-s average (VE/VCO 2 -Nadir) and from whole exercises (VE/VCO 2 -Total). Twelve prediction equations for VE/VCO 2 -slope were externally validated. Results: VE/VCO 2 -slope was higher in females than males (27.7 ± 2.6 vs. 26.1 ± 2.0, p < 0.001). Measuring methods for VE/VCO 2 differed significantly in males and females. VE/VCO 2 increased in EA with age independently from its type or sex (β = 0.066-0.127). Eleven equations underestimated VE/VCO 2 -slope (from -0.5 to -3.6). One equation overestimated VE/VCO 2 -slope (+0.2). Predicted and observed measurements differed significantly in nine models. Models explained a low amount of variance in the VE/VCO 2 -slope (R 2 = 0.003-0.031). Conclusions: VE/VCO 2 -slope, VE/VCO 2 -Nadir, and VE/VCO 2 -Total were significantly different in EA. Prediction equations for the VE/VCO 2 -slope were inaccurate in EA. Physicians should be acknowledged to properly assess cardiorespiratory fitness in EA.