However, seven participants registered a ⩒o2peak that was ≥ 3% lower on the CWR, which is important to consider because for these individuals, the additional test was not necessary to provide a more accurate measurement. Collectively, we believe these findings support our contention that ⩒o2max is not consistently achieved during RAMP-INC across a heterogeneous (i.e., with respect to sex and body composition) population of sedentary participants. The data that are presented in this article were collected as part of a cross-sectional trial that included performance of RAMP-INC to Tlim followed by CWR at 100% of WRpeak on RAMP-INC. The objective was to provide two opportunities for participants to achieve their ⩒o2max (assumed to be the higher of the two values), which was used for group matching for the evaluation that would follow.
The protocol was designed to obtain equivalent power output in succeeding intervals, for example 50 W in 3’, 100 W in 6’, 150 W in 9’, etc. The pedaling frequency remained above https://www.globalcloudteam.com/ 60 rev per minute and the test continued until volitional exhaustion. This main author of this work was supported by the Faculdade Estácio de Sá (Research Fellowship).
Incremental exercise test (IET)
However, it is important to note that only four of the 12 participants who did not achieve a greater ⩒o2peak during CWR were able to satisfy this criterion during RAMP-INC. While we cannot confirm that the RAMP-INC ⩒o2peak was ⩒o2max for these individuals (see above), it seems unlikely that it definitely was not for eight of the 12. Furthermore, this criterion HR value was equally difficult to achieve during CWR as only six of the 35 participants (all of whom also achieved it on RAMP-INC) were able to do so. This means that if this particular HR value was valid as a threshold indicator of the attainment of ⩒o2max (i.e., did not result in a high proportion of rejection of tests during which it actually was achieved), 29 of 35 participants in our study would not have achieved their ⩒o2max on either test. This seems unlikely, which implies that this value for HR is too stringent to be used for accepting that ⩒o2max has been achieved with this type of individual.
In other words, the usefulness of a severe-intensity CWR bout to limit of tolerance following INC might simply be to determine whether a higher ⩒o2peak can be elicited. Unlike an RER of 1.10 or 1.13, which was “easy” for participants to achieve (e.g., achieved at ~72% and ~76% of the highest ⩒o2peak attained across both tests, respectively), the criterion values for HR that we used in this study were more difficult for participants to surpass. For example, only three of the 23 individuals who achieved a higher ⩒o2peak on CWR compared to RAMP-INC achieved a HR during RAMP-INC that exceeded 95% of their age-predicted maximum (220 minus age), which was the traditional criterion that we employed. This supports the contention that achievement of a threshold level for HR might provide a useful way to identify RAMP-INC tests characterized by a submaximal ⩒o2peak for sedentary individuals.
This was also the case in a group of chronic heart failure patients (Bowen et al., 2012). These data could suggest that the verification phase provided a confirmation that a true V˙O2max was established in these subjects. However, these very same findings could just as plausibly indicate that the RI test per-se was an adequate protocol, yielding a true maximal response in most participants. Moreover, a recent study has shown that a verification phase resulted in a lower V˙O2 value as compared to that observed during a graded incremental test (McGawley, 2017). Importantly, the possible usefulness of a verification phase has only been investigated in relatively small and homogeneous samples and (with the exception of McGawley (2017)) with a suboptimal statistical approach (i.e., only comparison of mean values).
- The objective was to provide two opportunities for participants to achieve their ⩒o2max (assumed to be the higher of the two values), which was used for group matching for the evaluation that would follow.
- Buchfuhrer, M. J., Hansen, J. E., Robinson, T. E., Sue, D. Y., Wasserman, K., and Whipp, B. J.
- Cyclists reported to the laboratory after having abstained from eating the whole night (11 ± 1 h).
- The first test during this visit required participants to lie supine on a bed with a hood placed over their head so that gas exchange and ventilation could be measured for 60 min.
In addition, a strong correlation was observed between the FATmax intensity delineated in the RAMP test and AeT for the probed variables which were used in monitoring exercise intensity. In the present study, the verification phase at 85% and 105% of peak PO were collected in two different laboratories, which might represent a possible limitation. However, the equipment used in both laboratories was comparably accurate and precise and the experimental procedures were consistent between laboratories and clearly described to allow replication. Furthermore, since the analysis compares V˙O2 values obtained with the RI test and verification phase within each individual, whatever systematic bias in V˙O2 measures might exist between laboratories would affect both data-points in the same way. As for the vast majority of the studies that have described the use of a verification phase, the population tested in the present study is limited to male participants.
(A) The highest individual V˙O2 values observed during the verification phase (verification-V˙O2) are correlated with the values measured during the ramp incremental test (RI-V˙O2). The identity (dashed) and the correlation (solid) lines are displayed along with the correlation coefficient for the entire database. Data of subjects who completed the verification phase at 105 and 85% of maximal power output are displayed as filled (•) and empty circles (°) respectively. (B) Individual absolute differences (Δ V˙O2) between measures of the highest V˙O2 during the RI test and the verification phase are plotted as a function of the average of the two measures. Bias (dashed line) and precision (limits of agreement, dotted lines), for the entire database, are displayed along with the numerical values.
Journal of Exercise Science & Fitness
During both exercise tests, participants breathed through a low dead-space mouthpiece so that gas-exchange and ventilation data could be collected breath by breath (Carefusion Vmax Encore, Yorba Linda, CA). The gas analyzers were calibrated with gases of known concentration prior to each testing session and the flow sensor was calibrated using a 3-L syringe (Hans Rudolph Inc.). Blood pressure (SunTech Tango M2, Morrisville, NC), HR and ECG were also monitored continuously during the tests. The WRpeak and time to Tlim on RAMP-INC were recorded and participants rated their whole-body sense of effort at Tlim using the Borg RPE scale (6–20) immediately following the test. The participants were instructed to avoid hard training sessions during the data collection period (15–20 days) and not to ingest caffeine or any kind of stimulant for 6 h before the tests. Tests were scheduled at the same time of the day (afternoon; between 3 and 5 p.m.) and laboratory conditions were stable for the duration of the study (ambient temperature 20–22 °C, relative air humidity 50–60%).
That evaluation involved a nine-day investigation period which included moderate-intensity CWR bouts to assess the participant’s capacity for lipid oxidation. These bouts were performed at specific percentages of the gas exchange threshold measured during RAMP-INC; however, the ⩒o2peak measured during RAMP-INC was used to ensure that participants were of a similar level of conditioning (≤ average). No other data from the parent study have yet to be published and other than the group mean ± SD for ⩒o2peak, none of the data presented in the present article will be included in any other articles derived from the parent investigation when they are published. Although the verification phase appears appealing in providing a strategy to overcome the ongoing V˙O2 max-peak debate, data from different studies do not convincingly support the usefulness or necessity of a verification phase either in the general healthy population or in specific clinical/frail/unfit populations. In sedentary (Astorino et al., 2009), recreationally active (Sedgeman et al., 2013; Nolan et al., 2014), overweight and obese (Wood et al., 2010; Sawyer et al., 2015) adults, as well as children (Barker et al., 2011), the V˙O2 response during the verification phase was not higher than that observed during the RI test.
Achten et al. (2002) suggest that 3-min stages are optimal to reach a state of equilibrum and define MFO for well-trained athletes. Others recommend four to six longer (60 min) continuous exercise cycles, executed on separate days, at the intensity used in the IET (Meyer et al., 2007; Takagi et al., 2014). The latter approach may, however, be excessively time-consuming and therefore inconvenient in sports training.
There are limitations with the present study that deserve recognition. As previously mentioned, we chose a severe-intensity work rate for the CWR bout that was equal to the highest attained on the RAMP-INC. Hence, our protocol did not conform to the one that has been advanced for verification bouts which involve supramaximal work rates designed to test whether ⩒o2 can be driven to a higher value than that which was observed on RAMP-INC . However, being that we found that in 23 of 35 cases, ⩒o2 could be driven to a higher value during CWR even if it is performed at only the maximal work rate, it is intuitive that the same result would have been present if we had used a supramaximal work rate assuming it did not result in an “extreme” as opposed to severe domain-specific response. Nevertheless, future research involving post-INC CWR bouts at supramaximal work rates (e.g., 105% of WRpeak) and, perhaps, submaximal work rates that allow for longer duration CWR (e.g., 95% WRpeak) as well as multiple bouts to assess test-retest reliability will be important for providing more insight. Another limitation is that owing to the requirements of the parent study, participants performed the two-test sequence in a fasted state having refrained from consuming calorie-containing foods and beverages for 12 hrs.
Additionally, healthy older adults, for whom V˙O2max is the strongest predictor of independent living (Paterson and Warburton, 2010) and for whom a verification phase would theoretically be needed for accurate V˙O2max determination (Poole and Jones, 2017), have never previously been evaluated. Establishing if a verification phase actually adds confidence in the achievement of V˙O2max in this population would contribute to further support or oppose the recommendation of such practice. Several studies prescribed a more personalized approach with training recommendations based on HR values corresponding to the metabolic thresholds defined through IET (Ghosh, 2004; Meyer et al., 2005). That is why for the FATmax and FATmin points we present absolute and relative values of power and HR, as those variables are commonly used in controlling training intensity in cycling (Robinson et al., 2011). Available results suggest that both the metabolic thresholds and the points of fat oxidation are determined by the participants’ physical work capacity. In accordance with Meyer et al. (2005), it can then be concluded that the greater the athlete’s efficiency, the higher the intensity level at which he/she reaches his/her thresholds.
The idea that performing a verification phase at a given power output above that observed during the RI test to exhaustion is conceptually appealing as this procedure theoretically confirms that further increases in power output do not result in greater V˙O2 values (i.e., an upper limit plateau in the V˙O2 response). However, the evidence to support this type of statement appears surprisingly scant, and this idea neglects well-established concepts that show that exercising to the limit of tolerance at any intensity above critical power would result in attainment of V˙O2max. Endurance training should increase the potential of fat utilization in the process of energy production in order to preserve glycogen reserves used during high intensity exercise (breakaways, climbs, sprints) (Peric et al., 2016).
In conclusion, a severe-intensity CWR bout to limit of tolerance at the highest work rate achieved during a RAMP-INC test concluded 10 minutes prior resulted in a significantly higher ⩒o2peak compared to that which was reached on RAMP-INC for sedentary individuals. While we cannot confirm that CWR revealed the ⩒o2max in these cases, our findings suggest that giving this type of individual a second chance to achieve their highest ⩒o2 response during a subsequent CWR test that is ~70% shorter than RAMP-INC increases the likelihood that they will register a value that, if not their ⩒o2max, is at least closer to it. The popular and often-advocated criterion value of 1.10 for RER was too lenient for identifying RAMP-INC tests characterized by a submaximal ⩒o2peak as was the newly-proposed age-dependent value of 1.13. Conversely, the HR value of 95% of the age-predicted maximum appeared to be too stringent with the newly-proposed ones potentially reducing the chance of type II error at the expense of a greater likelihood of false acceptance.
Furthermore, even in cases where a supramaximal work rate is maintained during CWR, the fact that the work rate is endured during a separate bout (as opposed to one continuous one where work rate is increased throughout) means that it is conceivable that participants could simply stop exercising at the same submaximal ⩒o2 during both tests . This was important because we used this measurement to verify the sedentary status of our participants and to match the various groups that we were stratifying for comparison in our parent study. The purpose of the present study was to determine the degree to which an additional severe-intensity CWR bout and/or traditional and newly-proposed secondary criteria based on RER and HR might be valid methods to employ when attempting to verify ⩒o2max for sedentary individuals.