Increased Ventilatory Efficiency in Supramaximal Compared to Graded Exercise in Athletes.

Background : Supramaximal constant work rate tests (CWR) elicit intense hyperventilation, thus potentially up-shifting ventilation (⩒ _E )-to-carbon dioxide (CO ₂ ) responses when compared to graded exercise tests (GXT) in athletes. We predicted higher ventilatory efficiency on supramaximal CWR using a new method, challenging the classic orthodox interpretation of an increased ⩒ _E -⩒CO ₂ as ventilatory inefficiency. This misinterpretation could make difficult to differentiate between physiological hyperventilation from heart disease conditions in athletes. Methods : On different days, a GXT and a CWR at 110% of the maximal velocity achieved in the GXT were performed. Twenty-seven athletes completed the two tests and were compared for usual (linear regression) and log-transformed new variables for ventilatory efficiency through paired t -Student statistics. Results : The ⩒ _E -⩒CO ₂ slope (31.4 ± 4.9 vs . 26.2 ± 3.4, p  < .001), ⩒ _E -⩒CO ₂ intercept (7.2 ± 7.5 vs . 2.8 ± 4.2, p  < .007), ⩒ _E /⩒CO ₂ nadir (33.0 ± 3.6 vs . 25.4 ± 2.2, p  < .001), ⩒CO ₂ -log⩒ _E slope (10.8 ± 2.9 vs . 6.9 ± 2.2 L _* logL ^-1 , p  < .001), and η⩒ ^E (36.0 ± 12 vs . 22.8 ± 8.1%, p  < .001) values were all significantly higher in the CWR compared to the GXT. We registered a bi-modal nadir response for ⩒ _E/ ⩒CO ₂ on CWR for 22 out of 27 subjects for the first time. A weak association was observed between ⩒ _E /⩒CO ₂ nadir (coefficient of determination ~ 27%) and time to exhaustion. Conclusions : The new method allows us to improve the quantification and interpretation of ventilatory efficiency in athletes, avoiding misinterpretation due to the up-shifting elicited by the usual ⩒ _E -⩒CO ₂ slope and ⩒ _E /⩒CO ₂ nadir indices, which may be confounded with ventilatory inefficiency. This study suggests that ventilatory changes underpin better ventilatory efficiency during CWR.