A verification phase adds little value to the determination of maximum oxygen uptake in well-trained adults.

PURPOSE: The objective was to investigate if performing a sub-peak or supra-peak verification phase following a ramp test provides additional value for determining 'true' maximum oxygen uptake ( V ˙ O2). METHODS: 17 and 14 well-trained males and females, respectively, performed two ramp tests each followed by a verification phase. While the ramp tests were identical, the verification phase differed in power output, wherein the power output was either 95% or 105% of the peak power output from the ramp test. The recovery phase before the verification phase lasted until capillary blood lactate concentration was ≤ 4 mmol·L-1. If a V ˙ O2 plateau occurred during ramp test, the following verification phase was considered to provide no added value. If no V ˙ O2 plateau occurred and the highest V ˙ O2 ( V ˙ O2peak) during verification phase was < 97%, between 97 and 103%, or > 103% of V ˙ O2peak achieved during the ramp test, no value, potential value, and certain value were attributed to the verification phase, respectively. RESULTS: Mean (standard deviation) V ˙ O2peak during both ramp tests was 64.5 (6.0) mL·kg-1·min-1 for males and 54.8 (6.2) mL·kg-1·min-1 for females. For the 95% verification phase, 20 tests showed either a V ˙ O2 plateau during ramp test or a verification V ˙ O2peak < 97%, indicating no value, 11 showed potential value, and 0 certain value. For the 105% verification phase, the values were 26, 5, and 0 tests, respectively. CONCLUSION: In well-trained adults, a sub-peak verification phase might add little value in determining 'true' maximum V ˙ O2, while a supra-peak verification phase adds no value.

Is the maximal lactate steady state concept really relevant to predict endurance performance?

PURPOSE: There is no convincing evidence for the idea that a high power output at the maximal lactate steady state (PO_MLSS) and a high fraction of [Formula: see text]O2max at MLSS (%[Formula: see text]O2_MLSS) are decisive for endurance performance. We tested the hypotheses that (1) %[Formula: see text]O2_MLSS is positively correlated with the ability to sustain a high fraction of [Formula: see text]O2max for a given competition duration (%[Formula: see text]O2_TT); (2) %[Formula: see text]O2_MLSS improves the prediction of the average power output of a time trial (PO_TT) in addition to [Formula: see text]O2max and gross efficiency (GE); (3) PO_MLSS improves the prediction of PO_TT in addition to [Formula: see text]O2max and GE. METHODS: Twenty-one recreationally active participants performed stepwise incremental tests on the first and final testing day to measure GE and check for potential test-related training effects in terms of changes in the minimal lactate equivalent power output (∆PO_LEmin), 30-min constant load tests to determine MLSS, a ramp test and verification bout for [Formula: see text]O2max, and 20-min time trials for %[Formula: see text]O2_TT and PO_TT. Hypothesis 1 was tested via bivariate and partial correlations between %[Formula: see text]O2_MLSS and %[Formula: see text]O2_TT. Multiple regression models with [Formula: see text]O2max, GE, ∆PO_LEmin, and %[Formula: see text]O2_MLSS (Hypothesis 2) or PO_MLSS instead of %[Formula: see text]O2_MLSS (Hypothesis 3), respectively, as predictors, and PO_TT as the dependent variable were used to test the hypotheses. RESULTS: %[Formula: see text]O2_MLSS was not correlated with %[Formula: see text]O2_TT (r = 0.17, p = 0.583). Neither %[Formula: see text]O2_MLSS (p = 0.424) nor PO_MLSS (p = 0.208) did improve the prediction of PO_TT in addition to [Formula: see text]O2max and GE. CONCLUSION: These results challenge the assumption that PO_MLSS or %[Formula: see text]O2_MLSS are independent predictors of supra-MLSS PO_TT and %[Formula: see text]O2_TT.

Effect of intensive prior exercise on muscle fiber activation, oxygen uptake kinetics, and oxygen uptake plateau occurrence.

PURPOSE: We tested the hypothesis that the described increase in oxygen uptake ([Formula: see text])-plateau incidence following a heavy-severe prior exercise is caused by a steeper increase in [Formula: see text] and muscle fiber activation in the submaximal intensity domain. METHODS: Twenty-one male participants performed a standard ramp test, a [Formula: see text] verification bout, an unprimed ramp test with an individualized ramp slope and a primed ramp test with the same ramp slope, which was preceded by an intensive exercise at 50% of the difference between gas exchange threshold and maximum workload. Muscle fiber activation was recorded from vastus lateralis, vastus medialis, and gastrocnemius medialis using a surface electromyography (EMG) device in a subgroup of 11 participants. Linear regression analyses were used to calculate the [Formula: see text]-([Formula: see text]) and EMG-(∆RMS/∆P) ramp test kinetics. RESULTS: Twenty out of the 21 participants confirmed their [Formula: see text] in the verification bout. The [Formula: see text]-plateau incidence in these participants did not differ between the unprimed (n = 8) and primed (n = 7) ramp test (p = 0.500). The [Formula: see text] was lower in the primed compared to the unprimed ramp test (9.40 ± 0.66 vs. 10.31 ± 0.67 ml min-1 W-1, p < 0.001), whereas the ∆RMS/∆P did not differ between the ramp tests (0.62 ± 0.15 vs. 0.66 ± 0.14% W-1; p = 0.744). CONCLUSION: These findings do not support previous studies, which reported an increase in [Formula: see text]-plateau incidence as well as steeper increases in [Formula: see text] and muscle fiber activation in the submaximal intensity domain following a heavy-severe prior exercise.

Oxygen uptake plateau: calculation artifact or physiological reality?

PURPOSE: To test whether the oxygen uptake ([Formula: see text]) plateau at [Formula: see text] is simply a calculation artifact caused by the variability of [Formula: see text] or a clearly identifiable physiological event. METHODS: Forty-six male participants performed an incremental ramp and a [Formula: see text] verification test. Variability of the difference between adjacent sampling intervals (difference) and of the slope of the [Formula: see text]-workload relationship (slope) in the submaximal intensity domain were calculated. Workload defined sampling intervals used for the calculation of the difference and slope were systematically increased from 20 to 100 W until the expected risk of false plateau diagnoses based on the Gaussian distribution function was lower than 5%. Overall, more than 1500 differences and slopes were analyzed. Subsequently, frequencies of plateau diagnoses in the submaximal and maximal intensity domains were compared. RESULTS: Variability of the difference and slope decreased with increasing sampling interval (p < 0.001). At a sampling interval of 50 W, the predefined acceptable risk of false plateau diagnoses (≤ 5%) was achieved. At this sampling interval, the actual frequency (1.4%) of false-positive plateau diagnoses did not differ from the expected frequency in the submaximal intensity domain (1.6%; p = 0.491). In contrast, the actual frequency at maximal intensity (35.7%) was significantly higher compared to the submaximal intensity domain (p < 0.001) and even higher than the expected frequency of false-positive diagnoses (p < 0.001). CONCLUSION: The [Formula: see text] plateau at [Formula: see text] represents a physiological event and no calculation artifact caused by [Formula: see text] variability. However, detecting a [Formula: see text] plateau with sufficient certainty requires large sampling intervals.

Oxygen uptake plateau occurrence depends on oxygen kinetics and oxygen deficit accumulation.

We tested the hypothesis that participants with an oxygen uptake ( V ˙ O 2 ) plateau during incremental exercise exhibit a lower VO2 -deficit (VO2DEF )-accumulation in the submaximal intensity domain due to faster ramp and square wave O2 -kinetics. Twenty-six male participants performed a standard ramp test (increment: 30 W·min-1 ), a ramp test with an individualized ramp slope and a two-step (moderate and severe) square wave exercise followed by a V ˙ O 2 m a x -verification bout. VO2DEF was calculated by the difference between individualized ramp test V ˙ O2 and V ˙ O2 -demand estimated from steady-state V ˙ O2 -kinetics. Twenty-four participants verified their V ˙ O2max in the verification test. Ten of them showed a plateau in the individualized ramp test. VO2DEF at the end of this ramp test (4.34 ± 0.60 vs 4.54 ± 0.43 L) was not different between the plateau and the non-plateau group (P > 0.05). The plateau group had a significantly (P < 0.05) lower VO2DEF 2 minutes before termination of the individualized ramp test (2.24 ± 0.40 vs 2.78 ± 0.33 L). This coincided with a shorter mean response time (43 ± 9 vs 53 ± 7 seconds), a higher increase in V ˙ O2 per W (10.1 ± 0.2 vs 9.2 ± 0.5 mL·min-1 ·W-1 ) at the individualized ramp test as well as shorter time constants of moderate (36 ± 6 vs 48 ± 7 seconds) and severe (62 ± 9 vs 86 ± 10 seconds) square wave kinetics (all P < 0.05). We conclude that the V ˙ O2 -plateau occurrence requires a fast V ˙ O2 -kinetics and a low VO2DEF -accumulation at intensities below V ˙ O2max .

The Oxygen Uptake Plateau-A Critical Review of the Frequently Misunderstood Phenomenon.

A flattening of the oxygen uptake-work rate relationship at severe exercise indicates the achievement of maximum oxygen uptake [Formula: see text]. Unfortunately, a distinct plateau [Formula: see text] at [Formula: see text]is not found in all participants. The aim of this investigation was to critically review the influence of research methods and physiological factors on the [Formula: see text] incidence. It is shown that many studies used inappropriate definitions or methodical approaches to check for the occurrence of a [Formula: see text]. In contrast to the widespread assumptions it is unclear whether there is higher [Formula: see text] incidence in (uphill) running compared to cycling exercise or in discontinuous compared to continuous incremental exercise tests. Furthermore, most studies that evaluated the validity of supramaximal verification phases, reported verification bout durations, which are too short to ensure that [Formula: see text] have been achieved by all participants. As a result, there is little evidence for a higher [Formula: see text] incidence and a corresponding advantage for the diagnoses of [Formula: see text] when incremental tests are supplemented by supramaximal verification bouts. Preliminary evidence suggests that the occurrence of a [Formula: see text] in continuous incremental tests is determined by physiological factors like anaerobic capacity, [Formula: see text]-kinetics and accumulation of metabolites in the submaximal intensity domain. Subsequent studies should take more attention to the use of valid [Formula: see text] definitions, which require a cut-off at ~ 50% of the submaximal [Formula: see text] increase and rather large sampling intervals. Furthermore, if verification bouts are used to verify the achievement of [Formula: see text]/[Formula: see text], it should be ensured that they can be sustained for sufficient durations.

Comparison of V̇O2-Kinetic Parameters for the Management of Heart Failure.

Objective: The aim of this study was to analyze whether V̇O2-kinetics during cardiopulmonary exercise testing (CPET) is a useful marker for the diagnosis of heart failure (HF) and to determine which V̇O2-kinetic parameter distinguishes healthy participants and patients with HF. Methods: A total of 526 healthy participants and 79 patients with HF between 20 and 90 years of age performed a CPET. The CPET was preceded by a 3-min low-intensity warm-up and followed by a 3-min recovery bout. V̇O2-kinetics was calculated from the rest to exercise transition of the warm-up bout (on-kinetics), from the exercise to recovery transition following ramp test termination (off-kinetics) and from the initial delay of V̇O2 during the warm-up to ramp test transition (ramp-kinetics). Results: V̇O2 off-kinetics showed the highest z-score differences between healthy participants and patients with HF. Furthermore, off-kinetics was strongly associated with V̇O2peak. In contrast, ramp-kinetics and on-kinetics showed only minimal z-score differences between healthy participants and patients with HF. The best on- and off-kinetic parameters significantly improved a model to predict the disease severity. However, there was no relevant additional value of V̇O2-kinetics when V̇O2peak was part of the model. Conclusion: V̇O2 off-kinetics appears to be superior for distinguishing patients with HF and healthy participants compared with V̇O2 on-kinetics and ramp-kinetics. If V̇O2peak cannot be determined, V̇O2 off-kinetics provides an acceptable substitute. However, the additional value beyond that of V̇O2peak cannot be provided by V̇O2-kinetics.

Verification-phase tests show low reliability and add little value in determining [Formula: see text]O2max in young trained adults.

OBJECTIVE: This study compared the robustness of a [Formula: see text]-plateau definition and a verification-phase protocol to day-to-day and diurnal variations in determining the true [Formula: see text]. Further, the additional value of a verification-phase was investigated. METHODS: Eighteen adults performed six cardiorespiratory fitness tests at six different times of the day (diurnal variation) as well as a seventh test at the same time the sixth test took place (day-to-day variation). A verification-phase was performed immediately after each test, with a stepwise increase in intensity to 50%, 70%, and 105% of the peak power output. RESULTS: Participants mean [Formula: see text] was 56 ± 8 mL/kg/min. Gwet's AC1 values (95% confidence intervals) for the day-to-day and diurnal variations were 0.64 (0.22, 1.00) and 0.71 (0.42, 0.99) for [Formula: see text]-plateau and for the verification-phase 0.69 (0.31, 1.00) and 0.07 (-0.38, 0.52), respectively. In 66% of the tests, performing the verification-phase added no value, while, in 32% and 2%, it added uncertain value and certain value, respectively, in the determination of [Formula: see text]. CONCLUSION: Compared to [Formula: see text]-plateau the verification-phase shows lower reliability, increases costs and only adds certain value in 2% of cases.

New Data-based Cutoffs for Maximal Exercise Criteria across the Lifespan.

PURPOSE: To determine age-dependent cutoff values for secondary exhaustion criteria for a general population free of exercise limiting chronic conditions; to describe the percentage of participants reaching commonly used exhaustion criteria during a cardiopulmonary exercise test (CPET); and to analyze their oxygen uptake at the respective criteria to quantify the impact of a given criterion on the respective oxygen uptake (V˙O2) values. METHODS: Data from the COmPLETE-Health Study were analyzed involving participants from 20 to 91 yr of age. All underwent a CPET to maximal voluntary exertion using a cycle ergometer. To determine new exhaustion criteria, based on maximal respiratory exchange ratio (RERmax) and age-predicted maximal HR (APMHR), one-sided lower tolerance intervals for the tests confirming V˙O2 plateau status were calculated using a confidence level of 95% and a coverage of 90%. RESULTS: A total of 274 men and 252 women participated in the study. Participants were nearly equally distributed across age decades from 20 to >80 yr. A V˙O2 plateau was present in 32%. There were only minor differences in secondary exhaustion criteria between participants exhibiting a V˙O2 plateau and participants not showing a V˙O2 plateau. New exhaustion criteria according to the tolerance intervals for the age group of 20 to 39 yr were: RERmax ≥ 1.13, APMHR210 - age ≥ 96%, and APMHR208 × 0.7 age ≥ 93%; for the age group of 40 to 59 yr: RERmax ≥ 1.10, APMHR210 - age ≥ 99%, and APMHR208 × 0.7 age ≥ 92%; and, for the age group of 60 to 69 yr: RERmax ≥ 1.06, APMHR210 - age ≥ 99%, and APMHR208 × 0.7 age ≥ 89%. CONCLUSIONS: The proposed cutoff values for secondary criteria reduce the risk of underestimating V˙O2max. Lower values would increase false-positive results, assuming participants are exhausted although, in fact, they are not.

Higher energy and carbohydrate demand of interval training at a given average velocity on track versus treadmill.

We tested the hypothesis that because of acceleration and deceleration, the energy and carbohydrate demand are higher in interval training on a track than on a treadmill. Ten male subjects performed the same interval training on a treadmill and an outdoor track. A higher energy and carbohydrate demand on the track emphasizes that treadmill interval studies analyzing high numbers of short-lasting interval bouts are not transferable to interval running on a track.

In Athletes, the Diurnal Variations in Maximum Oxygen Uptake Are More Than Twice as Large as the Day-to-Day Variations.

In competitive sports any substantial individual differences in diurnal variations in maximal performance are highly relevant. Previous studies have exclusively focused on how the time of day affects performance and disregarded the maximal individual diurnal variation of performance. Thus, the aims of this study were (1) to investigate the maximum diurnal variation in maximum oxygen uptake (VO2max), (2) to compare the diurnal variation of VO2max during the day to the day-to-day variation in VO2max, and (3) to investigate if there is a time-of-day effect on VO2max. Ten male and seven female athletes (mean VO2max: 58.2 ± 6.9 ml/kg/min) performed six maximal cardiopulmonary exercise tests including a verification-phase at six different times of the day (i.e., diurnal variation) and a seventh test at the same time the sixth test took place (i.e., day-to-day variation). The test times were 7:00, 10:00, 13:00, 16:00, 19:00, and 21:00. The order of exercise tests was the same for all participants to ensure sufficient recovery but the time of day of the first exercise test was randomized. We used paired t-tests to compare the nadir and peak of diurnal variations, day-to-day variations and the difference between diurnal and day-to-day variations. The mean difference in VO2max was 5.0 ± 1.9 ml/kg/min (95% CI: 4.1, 6.0) for the diurnal variation and 2.0 ± 1.0 ml/kg/min (95% CI: 1.5, 2.5) for the day-to-day variation. The diurnal variation was significantly higher than the day-to-day variation with a mean difference of 3.0 ± 2.1 ml/kg/min (95% CI: 1.9, 4.1). The linear mixed effects model revealed no significant differences in VO2max for any pairwise comparison between the different times of the day (all p > 0.11). This absence of a time-of-day effect is explained by the fact that peak VO2max was achieved at different times of the day by different athletes. The diurnal variations have meaningful implications for competitive sports and need to be considered by athletes. However, the results are also relevant to research. To increase signal-to-noise-ratio in intervention studies it is necessary to conduct cardiopulmonary exercise testing at the same time of the day for pre- and post-intervention exercise tests.

Which Cutoffs for Secondary V˙O2max Criteria Are Robust to Diurnal Variations?

PURPOSE: The aim was to determine the minimum maximum oxygen uptake (V˙O2max) criteria cut-offs in highly trained athletes (i.e., maximum RER [RERmax], maximum HR [HRmax], maximum RPE [RPEmax], and maximum blood lactate concentration [BLmax]) necessary to determine maximum oxygen uptake (V˙O2max) during cardiopulmonary exercise tests (CPET), by balancing type I and type II errors. A further aim was to investigate if the defined cutoffs would be robust to diurnal and to day-to-day variations. METHODS: Data from two CPET studies involving young athletes were analyzed. In the first study, 70 male participants performed one CPET until exhaustion to define cutoffs. In the second study, eight males and five females performed one CPET on seven consecutive days at six different times of day (i.e., diurnal variation). The time of the CPET was identical on the sixth and seventh days (i.e., day-to-day variation). To ensure comparability both studies were carried out under the same conditions. RESULTS: Participants' mean V˙O2max was 63.0 ± 5.3 mL·kg·min. RERmax ≥1.10 was reached by 100%, HRmax ≥95% of age-predicted HRmax by 99%, RPEmax ≥19 by 100%, and BLmax ≥8 mmol·L by 100% of participants, respectively. Regarding the intraday variations, latter cutoffs were not reached in two cases for RERmax and in one case for HRmax and BLmax. Intraclass correlations for the day-to-day variability were r = 0.823 for RERmax, r = 0.828 for HRmax, and r = 0.380 for BLmax, respectively. CONCLUSIONS: The proposed high cut-off values for secondary criteria provide some assurance that V˙O2max may have been achieved in athletes without increasing type II errors. However, type I errors may still occur indicating that further methods such as V˙O2-plateau or V˙O2-validation may be required.