The importance of the verification phase following an incremental exercise to ensure maximum oxygen consumption.

Abstract

The purpose of this study was to analyze cardiac output (Qc), stroke volume (SV), heart rate (HR), and arterio-venous O<inf>2</inf> difference (a-vO<inf>2diff</inf>) responses throughout a graded exercise test (GXT) and verification phase (VP) to examine whether SV decrement during the GXT is a main factor for underestimation of the maximal O<inf>2</inf> uptake (V̇O<inf>2max</inf>), or not. Seven well-trained male cyclists volunteered for this study (V̇O<inf>2max</inf>: 61.7±6.13 mL∙min-1∙kg-1). Following submaximal tests, participants were asked to perform GXT until exhaustion. Then, multisession verifications were performed on different days using ±3% constant work rates. The highest 30-second mean of V̇O<inf>2</inf> was considered as the V̇O<inf>2max</inf> and corresponding external power as peak power output (PPO). The Qc, SV, HR, and a-vO<inf>2diff</inf> responses were evaluated at both GXT and VP by nitrous-oxide rebreathing method. After repeated-measures analyses, possible significant differences were investigated by LSD/Wilcoxon. It was shown that the HR and a-vO<inf>2diff</inf> reached their potentially highest values at the end of the both GXT and VP (192.9±8.8 vs. 190.7±7.9 bpm; 17.1±1.6 vs. 16.9±1.1%, respectively; P>0.05); however, SV (128.8±11.2 vs. 137.3±11.2 mL; P=0.029) and Qc (24.8±2.02 vs. 26.2±2.71 L·min-1; P=0.046) were lower at GXT when compared to the VP. V̇O<inf>2</inf> means were, therefore, higher in VP when compared to the GXT (61.7±6.13 vs. 59.1±6.2 mL∙min-1∙kg-1; P=0.041). The GXT provided only a peak V̇O<inf>2</inf> but not the V̇O<inf>2max</inf>. Consequently, the real V̇O<inf>2max</inf> and PPO could be provided by only VP administrations. This is likely to result from the lower Qc and SV responses observed from a prolonged incremental test protocol when compared to short bouts of constant work rate trials.