Evaluation Of Maximal Oxygen Uptake Using Verification Phases Of Different Intensities Across Fitness Levels

Abstract

Confirmation of maximal oxygen consumption (V˙O2max) has relevance in both clinical and exercise settings. Though there are criteria in place to confirm V˙O2max has been attained, they are inconsistently achieved. For example, a plateau in V˙O2 with a corresponding increase in workload is often absent, and other criteria such as a respiratory exchange ratio (RER) ≥1.15 or heart rate (HR) within 10 beats per min (bpm) of age predicted maximum can result in an inaccurate estimate of V˙O2max. Due to these shortcomings, some researchers have suggested the use of a verification phase (VP) to confirm the attainment of V˙O2max. PURPOSE: Therefore, this study aimed to provide further evidence for the need to use a VP with V˙O2max testing protocols in populations of different fitness levels. METHODS: 49 participants (M: 27, F: 22; 21.9±2.6 y, 24.3±2.8 kg·m2) had their V˙O2 and HR measured during three maximal graded treadmill tests with each test followed by a VP of differing intensity (85%, 95%, 105% final workload). Participants were divided into groups based on their V˙O2max using norms adapted from American College of Sports Medicine (ACSM) V˙O2max guidelines (poor, fair, good, excellent) resulting in 7, 19, 18, and 5 participants respectively. V˙O2max from the graded treadmill test was confirmed with the VP and/or an additional test if the highest V˙O2 value achieved was no more than 2 x typical error (TE: 1.9 to 3.7 mL·kg-1·min-1 across groups). RESULTS: Plateau was achieved on 43/147 tests (29%), RER ≥ 1.15 was achieved on 104/147 tests (71%), HR within 10 bpm of age-predicted max was achieved on 83/147 tests (56%), and volitional fatigue was reached on 147/147 tests (100%). The highest V˙O2 value attained on the initial V˙O2max test was not different than either value attained following the VP at 95 or 105% of final V˙O2max test workload or a second repeat test on a separate day (P>0.211). The 85% VP V˙O2 value was lower than the initial V˙O2max test value (P<0.001). CONCLUSION: While traditional criteria to confirm the attainment of V˙O2max were inconsistently achieved, the use of a VP (at 95 or 105%) or a subsequent repeat test on a separate day were able to confirm the V˙O2max value attained. Our data also suggests exercise studies employing only a single V˙O2max test should consider these inconsistencies across a range of fitness levels.