Verification Phase Confirms V̇O2max in a Hot Environment in Sedentary Untrained Males

Abstract

The verification phase is becoming the norm for confirming VO 2max during a graded exercise test (GXT), but the use of such testing in untrained participants in the heat remains unknown. Purpose: This study aimed to assess the VO 2 uptake obtained during a GXT and subsequent verification phase in untrained participants in a hot environment. Methods: Twelve sedentary males completed a GXT followed by a biphasic supramaximal-load verification phase in a hot environment (39°C, 32% relative humidity). Rest between tests occurred in a temperate chamber and lasted until gastrointestinal temperature returned to baseline. Results: Mean verification phase VO 2max (37.8 ± 4.3 mL•kg −1 •min −1 ) was lower than GXT (39.8 ± 4.1 mL•kg −1 •min −1 ; P = 0.03) and not statistically equivalent. Using an individualized analysis approach, only 17% (2/12) of participants achieved a VO 2 plateau during the GXT. Verification phase confirmed GXT VO 2max in 100% of participants, whereas the traditional and the new age-dependent secondary VO 2max criteria indicated GXT VO 2max achievement at much lower rates (8/12 [67%] vs 7/12 [58%], respectively). Correlational indices between GXT and verification phase VO 2max were strong (intraclass correlation coefficient = 0.95, r = 0.86), and Bland-Altman analysis revealed a low mean bias of −2.1 ± 1.9 mL•kg −1 •min −1 and 95% limits of agreement (−5.8 to 1.7 mL•kg −1 •min −1 ). Conclusions: Very few untrained males achieved a VO 2 plateau during GXT in the heat. When conducting GXT in a hot condition, the verification phase remains a valuable addition to confirm VO 2max in untrained males.

Analysis of Individual V˙O2max Responses during a Cardiopulmonary Exercise Test and the Verification Phase in Physically Active Women

“…Previous work [ 27 , 28 , 29 ] has used the MD to examine the individual differences in the O 2CPET and O 2verification in treadmill running in men and women and in cycle ergometry in men. These works, in addition to others [ 4 , 25 , 30 ], demonstrated that young healthy subjects accustomed to exhaustive exercise seldom demonstrate differences between the O 2CPET and O 2verification , and in some cases, they demonstrate no differences at all. The lack of individual subjects who demonstrate O 2verification values that are either equivalent or are significantly less than the O 2CPET [ 4 , 25 , 27 , 28 , 29 ] support previous work [ 23 ] that has questioned the need for the verification phase in measuring the O 2max in all populations and settings.…”

“…These works, in addition to others [ 4 , 25 , 30 ], demonstrated that young healthy subjects accustomed to exhaustive exercise seldom demonstrate differences between the O 2CPET and O 2verification , and in some cases, they demonstrate no differences at all. The lack of individual subjects who demonstrate O 2verification values that are either equivalent or are significantly less than the O 2CPET [ 4 , 25 , 27 , 28 , 29 ] support previous work [ 23 ] that has questioned the need for the verification phase in measuring the O 2max in all populations and settings. The additional benefit of the quantification of the MD in specific populations and in different modalities is that future works, such as training or nutritional interventions, are able to use the MD as a threshold by which individual responses can be examined without the need to perform verification phases.…”

“…Previous work investigating the need for a verification phase in the determination of the O 2max has examined the mean responses of the O 2 determined from the CPET compared to the O 2 determined from the verification phase. Other works have demonstrated no mean difference in the O 2max between the CPET and verification phase, yet still recommend its use in all populations [ 8 , 25 ]. However, as has been previously pointed out [ 23 , 24 ], the examination of the individual responses is more important than the mean responses in regard to the attainment of the highest O 2 ( O 2max ).…”

“…Using this threshold, Weatherwax et al [ 4 ] demonstrated 2.6% of subjects (4 out of 156 tests) demonstrated a 3% difference between the O 2CPET and O 2verification . Other more recent work [ 25 ] has extrapolated the O 2 versus work rate relationship to predict the O 2verification and used the predicted value as a method to confirm the individual attainment of the O 2max following the recommendation of Midgley et al [ 26 ]. These authors [ 25 ] demonstrated that the O 2verification was on average 5% lower than the O 2CPET , but that on an individual basis, the O 2max was ‘confirmed’ in all participants since the difference between the predicted and actual O 2max was less than half the regression slope [ 25 , 26 ].…”

“…Other more recent work [ 25 ] has extrapolated the O 2 versus work rate relationship to predict the O 2verification and used the predicted value as a method to confirm the individual attainment of the O 2max following the recommendation of Midgley et al [ 26 ]. These authors [ 25 ] demonstrated that the O 2verification was on average 5% lower than the O 2CPET , but that on an individual basis, the O 2max was ‘confirmed’ in all participants since the difference between the predicted and actual O 2max was less than half the regression slope [ 25 , 26 ]. While this method represents an improvement upon the 3% threshold, this may not serve as a threshold for future studies to use to examine individual responses.…”