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Is the VO2max that we measure really maximal?

Is the VO2max that we measure really maximal? OPINION ARTICLE published: 05 August 2013 doi: 10.3389/fphys.2013.00203 Is the VO max that we measure really maximal? 1 1,2 1 Bruno P. C. Smirmaul *, Danilo R. Bertucci and Inaian P. Teixeira Department of Physical Education, São Paulo State University (UNESP), Rio Claro, Brazil Department of Physiological Sciences, Federal University of São Carlos (UFSCAR), São Carlos, Brazil *Correspondence: [email protected] Edited by: Simon C. Gandevia, Neuroscience Research Australia, Australia INTRODUCTION proposed the existence of an individual this model proposes that there is always a exercise intensity beyond which there is no physiological reserve, both cardiovascular The maximal oxygen uptake (VO max) can be defined as the maximum integrated increase in the VO ,representing the limit and neuromuscular, once the number of of the cardiorespiratory capacity. However, motor unit recruited by the active muscles capacity of the pulmonary, cardiovascular the need for the plateau occurrence to during exercise is regulated by the brain and muscular systems to uptake, trans- the VO max determination presents lim- to prevent catastrophic failure in bodily port and utilize O , respectively (Poole 2 itations, once it conflicts with the fact that systems (Noakes and Marino, 2009). et al., 2008). Usually measured by the its occurrence is not universal (Doherty incremental exercise test in the tread- et al., 2003; Astorino et al., 2005). With the IS THE VO maxTHAT WEMEASURE mill or cycle ergometer, the VO max test purpose to solve this problem and ensure REALLY MAXIMAL? has become a cornerstone in clinical and that individuals attain always “maximal” applied physiology involving physical exer- Independently of the VO max conditions by the end of an incremental limiting/regulatory mechanisms (Ekblom, cise. Its applications are numerous, rang- exercise test, producing true VO max val- ing from elite athletes to individuals with 2 2009; Noakes and Marino, 2009), it several pathologic conditions (Mancini ues, the use of physiological parameters as is believed that implementing specific criteria for exercise test interruption based et al., 1991; Bassett and Howley, 2000). criteria during the incremental exercise upon respiratory exchange ratio, maximal Despite studied for approximately a cen- test as duration (Midgley et al., 2008), heart rate and blood lactate concentrations tury, questions regarding the VO max presence of the “verification phase” (Day became popular (Poole et al., 2008). These are still source of debate and disagree- et al., 2003; Midgley and Carroll, 2009), parameters, though, when used as criteria and rate of VO sample acquisition ment in the literature (Noakes, 1998; for VO max determination, can underesti- Bergh et al., 2000; Levine, 2008; Ekblom, (Astorino, 2009), one obtains true mate the actual measured value up to 26% VO max values. Two recent studies, 2009; Noakes and Marino, 2009; Spurway (Poole et al., 2008). Finally, the current et al., 2012). In particular, the study of however, challenge such beliefs. solution proposed to VO max determina- The first study (Mauger and the methods of VO max measurement 2 tion when the plateau does not occur, is the is a field of investigation that has been Sculthorpe, 2012)compared a conven- challenging through the years (Midgley use of the VO peak, which seems to be a tional incremental exercise test (i.e., with consistent VO max index, aslongasacon- et al., 2007, 2008). Intriguing findings 2 fixed load increments until voluntary stant supramaximal exercise test is done recently published (Beltrami et al., 2012; exhaustion) with a maximal self-paced after the incremental test, called “verifica- Mauger and Sculthorpe, 2012) bring addi- incremental exercise test regulated by tion phase” (Day et al., 2003; Midgley and tional debate regarding the measurement individual perception of effort. The Carroll, 2009). of the true VO max value and its limit- total duration of the latter was 10 min, Presently, two main theoretical mod- ing/regulatory mechanisms. In this article distributed in 5 stages of 2 min each, in els are discussed in the literature aiming which individuals controlled the exercise we briefly describe the current testing to explain the mechanisms of VO max methods and mechanisms of VO max lim- intensity at each moment in order to limitation and/or regulation. The classical achieve individual perceptions of effort itation/regulation, and discuss the new model proposes that VO max is limited by findings of these two recent studies and of 11, 13, 15, 17, and 20, respectively, in the maximal capacity of the heart to pro- the 15-points Borg scale. Interestingly, their possible implications in the field. vide O to the muscles, that means, when 2 this maximal self-paced incremental test one reaches the VO max the cardiovascu- resulted in a significantly higher VO max CURRENT MEASUREMENT AND lar system is working on its limit (Ekblom, (≈ 8%; Figure 1A)whencompared to VO max LIMITING/REGULATORY 2009). Alternatively, the other model advo- the values found during the conventional MECHANISMS cates that the cardiovascular system never incremental exercise test (Mauger and One of the most popular concepts used reaches a limit of work, and that VO max Sculthorpe, 2012). to obtain VO max during an incremental is regulated, rather than limited, by the The second study (Beltrami et al., 2012) exercise test is the occurrence of the number of motor unit recruited in the compared a conventional incremental plateau. The origin of this concept had exercising limbs, which is always submax- exercise test with a decremental protocol its basis in the studies of Hill and imal (Noakes and Marino, 2009). Thus, Lupton (1923) 90 years ago, in which they (i.e., with decreasing exercise intensity www.frontiersin.org August 2013 | Volume 4 | Article 203 | 1 Smirmaul et al. Is VO max really maximal? FIGURE 1 | (A) VO and power output data for the self-paced for the decremental protocol (right) in a representative subject. A incremental protocol (top) and conventional incremental protocol higher VO max (group mean ≈ 4.4%) was achieved in the (bottom) in a representative subject. A higher VO max (group decremental protocol during submaximal workload. VO is 2 2 mean ≈ 8%) was achieved in the self-paced incremental protocol represented by solid lines, and dotted lines represent speed. during submaximal workload. (B) VO and speed data for the “Reproduced from Mauger and Sculthorpe (2012) and Beltrami conventional incremental test (left) + verification phase (middle) and et al. (2012) with permission from BMJ Publishing Group Ltd.” levels over time). This decremental pro- reduction in the anaerobic component of values found (Beltrami et al., 2012; tocol started in the speed used during the the test, and/or an increase in the oxy- Mauger and Sculthorpe, 2012)uponthe “verification phase” of the incremental gen demand and utilization due to the existing body of knowledge relating to −1 test, which means, 1 km h faster than high power output in the last stage of this area? In our opinion, a consider- the last stage accomplished during the the self-paced incremental test, may also able portion of the scientific knowledge conventional exercise test. This intensity have contributed to the greater VO max would be mildly affected, due to the exis- was kept for 60% of the individual time found (Mauger and Sculthorpe, 2012). It tence of systematic error. For instance, that subjects were able to tolerate during is noteworthy that criticisms have already studies aiming to verify the effect of spe- the “verification phase,” with a subsequent been raised to this study (Chidnok et al., cific interventions upon VO max already −1 reduction in speed of 1 km h for 30 s 2013). At thesametime the authors of have VO max underestimations aggre- −1 and consecutive reductions of 0.5 km h , the second study (Beltrami et al., 2012) gated into their results. As pre- and post- in which each stage was kept for 30, 45, suggest that differences in the anticipa- intervention values are measured by the 60, 90, and 120 s, respectively. Similarly tory workload perception of the protocols, same protocol, the intervention effects to the maximal self-paced incremental growing in the conventional incremen- upon VO max values would still be cor- test (Mauger and Sculthorpe, 2012), the tal test and reducing in the decremental rectly measured, despite underestimation decremental test proposed resulted in test, might have impacted the sympathetic of VO max true value. In contrast, studies significantly higher VO max (≈ 4.4%; or parasympathetic drives and led to based upon VO max percentages, as the 2 2 Figure 1B) when compared to the conven- different metabolic responses to exercise aerobic training zone for cardiorespira- tional incremental exercise test (Beltrami and to the greater VO max. Surprisingly, tory fitness, for example, which habitually et al., 2012). both studies showed that either untrained varies around 50 and 85% of VO max, The main explanation suggested by (Mauger and Sculthorpe, 2012), or trained would have its interval range shifted to the authors for the results found in (Beltrami et al., 2012) individuals attained the right. Likewise, it would be neces- the first study (Mauger and Sculthorpe, the greater VO max values during sub- sary to review the indirect equations 2012) is that the nature of the self- maximal workloads, challenging the tradi- to estimate VO max, as they make use paced protocol may have allowed a higher tional concept that VO max occurs at the of VO max reference values that are, 2 2 power output for the same level of per- maximal workload. according to the new findings (Beltrami ception of effort or discomfort, lead- et al., 2012; Mauger and Sculthorpe, ing to greater VO max before voluntary IMPLICATIONS OF THE NEW FINDINGS 2012), submaximal. Nevertheless, know- exhaustion. This occurred despite heart ing the underestimation magnitude of Once recognized and further corrobo- rate, ventilation, and respiratory exchange rated that current VO max measurement the VO max by the conventional incre- 2 2 ratiovalues being similar tothe conven- methods (i.e., conventional incremental mental protocols, mathematical equations tional protocol. Additional suggestions as would be able to provide a posteriori exercise protocol) provide, in fact, a greater relative contribution of oxygen- submaximal values, which would be the corrections, reducing/correcting such dependent type 1 fibers with a consequent inaccuracies. implications of the new true VO max Frontiers in Physiology | Exercise Physiology August 2013 | Volume 4 | Article 203 | 2 Smirmaul et al. Is VO max really maximal? Contrary to the relatively minor impact emphasizes the paramount importance of determinants of endurance performance. Med. Sci. Sports Exerc. 32, 70–84. described above, the findings of greater effort on endurance exercise performance Beltrami,F.G., Froyd, C.,Mauger, A. R.,Metcalfe, VO max than the ones commonly found regulation and tolerance (Marcora and A. J., Marino, F., and Noakes, T. D. (2012). during conventional incremental exercise Staiano, 2010; Smirmaul et al., 2013). The Conventional testing methods produce submaxi- tests conflict with the theoretical models higher VO max values achieved (Beltrami 2 mal values of maximum oxygen consumption. Br. proposed to explain its limiting/regulatory et al., 2012; Mauger and Sculthorpe, 2012) J. Sports Med. 46, 23–29. doi: 10.1136/bjsports- 2011-090306 mechanisms (Ekblom, 2009; Noakes and may have been associated with altered per- Bergh, U., Ekblom, B., and Astrand, P. O. (2000). Marino, 2009). If the VO max values ceptual responses due to the differences in Maximal oxygen uptake “classical” versus “con- found so far during conventional incre- the protocols used. However, this possibil- temporary” viewpoints. Med. Sci. Sports Exerc. 32, mental tests are limited by the maximal ity remains speculative. 85–88. Billat, V., Petot, H., Karp,J.R., Sarre, G.,Morton, capacity of the heart to provide O to R. H., and Mille-Hamard, L. (2013). The sus- CONCLUSION the muscles (Ekblom, 2009), how can one tainability of VO2max: effect of decreasing the The proposals of different exercise proto- explain such an increase (Beltrami et al., workload. Eur. J. Appl. Physiol. 113, 385–394. doi: cols which result in greater VO max values 2012; Mauger and Sculthorpe, 2012)? We 2 10.1007/s00421-012-2424-7 than commonly found during the con- identify two possibilities. The theoretical Chidnok, W., Dimenna, F. J., Bailey, S. J., Burnley, M., Wilkerson, D. P., Vanhatalo, A., et al. (2013). ventional incremental exercise tests should model may still be correct, that means, VO2max is not altered by self-pacing during incre- interest the exercise and sports physiol- VO max is indeed limited by the maximal mental exercise: reply to the letter of Alexis, R. ogy community. At the same time that capacity of the heart, though, the VO max Mauger. Eur. J. Appl. Physiol. 113, 543–544. doi: such findings mildly impact a consid- values found during conventional incre- 10.1007/s00421-012-2563-x mental tests are not truly maximal, and erable portion of knowledge, they chal- Day, J. R., Rossiter, H. B.,Coats, E.M., Skasick, A.,and Whipp, B. J. (2003). The maximally attainable VO2 lenge, for instance, the theoretical models alternative protocols would be able to during exercise in humans: the peak vs. maximum increase it. In opposition, the model may to explain VO max limitation/regulation. issue. J. Appl. Physiol. 95, 1901–1907. Still, they also challenge the concept that be wrong in stating that VO max is pri- Doherty, M., Nobbs, L., and Noakes, T. D. (2003). marily limited by the cardiac capacity, VO max occurs at the maximal work- Low frequency of the “plateau phenomenon” dur- load. While recent work has shown that ing maximal exercise in elite British athletes. Eur. and another mechanism might exist to J. Appl. Physiol. 89, 619–623. doi: 10.1007/s00421- it is possible to maintain a conventional explain its limitation/regulation. The other 003-0845-z VO max plateau up to 15 min by decreas- theoretical model (Noakes and Marino, 2 Ekblom, B. (2009). Counterpoint: maximal oxygen ing individuals’ workload, that means, 2009), on its turn, also conflicts with the uptake is not limited by a central nervous system during submaximal work (Petot et al., findings. If the brain regulates the num- governor. J. Appl. Physiol. 106, 339–341. discus- 2012; Billat et al., 2013), it is unknown sion: 341–342. ber of motor unit recruited during exer- Hill, A. V., and Lupton, H. (1923). Muscular exer- whether the same is possible for the cise in order to prevent catastrophic fail- cise, lactic acid, and the supply and utiliza- superior VO max values found (Beltrami ure in bodily systems, thus regulating the tion of oxygen. Q. J. Med. 16, 135–171. doi: VO max achievable, why would the brain et al., 2012; Mauger and Sculthorpe, 2012). 10.1093/qjmed/os-16.62.135 The suggestion that VO max values are allow individuals during these two new 2 Jones, N. L., and Killian, K. J. (2000). Exercise limi- tation in health and disease. N. Engl. J. Med. 343, protocols (Beltrami et al., 2012; Mauger task-dependent, and that the conventional 632–641. doi: 10.1056/NEJM200008313430907 incremental exercise test does not produce and Sculthorpe, 2012) to attain VO max Levine, B. D. (2008). VO2max: what do we true maximal values is attractive. However, values greater than during the conven- know, and what do we still need to know. understanding how these new exercise tional incremental tests? Would not the J. Physiol. 586, 25–34. doi: 10.1113/jphysiol.2007. protocols produce higher VO max values, brain, based on afferent feedback from 147629 Mancini, D. M., Eisen, H., Kussmaul, W., Mull, R., the influences of different protocols on various systems, regulate the number of Edmunds, L. H., and Wilson, J. R. (1991). Value perceptual responses and VO max mea- motor unit recruited in a similar fash- of peak exercise oxygen consumption for opti- surement, determining its full implications ion, independently of the exercise protocol mal timing of cardiac transplantation in ambu- and applications, and the specific limit- performed? latory patients with heart failure. Circulation 83, A possible explanation for the recent ing/regulatory mechanisms underpinning 778–786. doi: 10.1161/01.CIR.83.3.778 Marcora, S. M., and Staiano, W. (2010). The limit VO max, are new horizons that sports and findings may be found reaching back 2 to exercise tolerance in humans: mind over mus- exercise scientists may explore. to the proposal by Jones and Killian cle. Eur. J. Appl. Physiol. 109, 763–770. doi: (2000), who reviewed evidence to show 10.1007/s00421-010-1418-6 that, rather than limitations based on the Mauger, A. R., and Sculthorpe, N. (2012). A REFERENCES Astorino, T. A. (2009). Alterations in VOmax and new VO2max protocol allowing self-pacing capacity of oxygen-delivery mechanisms, in maximal incremental exercise. Br.J.Sports the VO plateau with manipulation of sampling cardiorespiratory and exercise limitations interval. Clin. Physiol. Funct. Imaging 29, 60–67. Med. 46, 59–63. doi: 10.1136/bjsports-2011- are symptom-based. 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A recent theoretical model further 10.2165/00007256-200838060-00001 factors for maximum oxygen uptake and www.frontiersin.org August 2013 | Volume 4 | Article 203 | 3 Smirmaul et al. Is VO max really maximal? Midgley, A. W., and Carroll, S. (2009). Emergence Petot, H., Meilland, R., Le Moyec, L., Mille-Hamard, September 2010. J. Sports Sci. 30, 517–531. doi: of the verification phase procedure for con- L., and Billat, V. L. (2012). A new incremental test 10.1080/02640414.2011.642809 firming “true” VO(2max). Scand. J. Med. Sci. for VO2max accurate measurement by increasing Sports 19, 313–322. doi: 10.1111/j.1600-0838.2009. VO2max plateau duration, allowing the investiga- Received: 28 June 2013; accepted: 18 July 2013; 00898.x tion of its limiting factors. Eur. J. Appl. Physiol. 112, published online: 05 August 2013. Midgley, A. W.,McNaughton, L. R.,Polman, R., 2267–2276. doi: 10.1007/s00421-011-2196-5 Citation: Smirmaul BPC, Bertucci DR and Teixeira IP and Marchant, D. (2007). Criteria for determina- Poole, D. C., Wilkerson, D. P., and Jones, A. M. (2008). (2013) Is the VO max that we measure really maximal? tion of maximal oxygen uptake: a brief critique Validity of criteria for establishing maximal O2 Front. Physiol. 4:203. doi: 10.3389/fphys.2013.00203 and recommendations for future research. Sports uptake during ramp exercise tests. Eur. J. Appl. This article was submitted to Frontiers in Exercise Med. 37, 1019–1028. doi: 10.2165/00007256- Physiol. 102, 403–410. doi: 10.1007/s00421-007- Physiology, a specialty of Frontiers in Physiology. 200737120-00002 0596-3 Copyright © 2013 Smirmaul, Bertucci and Teixeira. Noakes, T. D. (1998). Maximal oxygen uptake: Smirmaul,B. P. C., Dantas,J.L., Nakamura, F. Y., This is an open-access article distributed under the terms “classical” versus “contemporary” view- Pereira, G. (2013). The psychobiological model: of the Creative Commons Attribution License (CC BY). points: a rebuttal. Med. Sci. Sports Exerc. 30, a new explanation to intensity regulation and The use, distribution or reproduction in other forums 1381–1398. (in)tolerance in endurance exercise. Rev. Bras. is permitted, provided the original author(s) or licen- Noakes, T. D., and Marino, F. E. (2009). Point: maxi- Educ. Fis. Esporte. 27, 333–340. sor are credited and that the original publication in mal oxygen uptake is limited by a central nervous Spurway, N. C.,Ekblom, B.,Noakes, T. D.,and this journal is cited, in accordance with accepted aca- system governor. J. Appl. Physiol. 106, 338–339. Wagner, P. D. (2012). What limits [V(·)]O(2max). demic practice. No use, distribution or reproduction is discussion: 341. A symposium held at the BASES Conference, 6 permitted which does not comply with these terms. Frontiers in Physiology | Exercise Physiology August 2013 | Volume 4 | Article 203 | 4 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Frontiers in Physiology Unpaywall

Is the VO2max that we measure really maximal?

Smirmaul, Bruno P. C.; Bertucci, Danilo R.; Teixeira, Inaian P.
Frontiers in Physiology – Jan 1, 2013
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OPINION ARTICLE published: 05 August 2013 doi: 10.3389/fphys.2013.00203 Is the VO max that we measure really maximal? 1 1,2 1 Bruno P. C. Smirmaul *, Danilo R. Bertucci and Inaian P. Teixeira Department of Physical Education, São Paulo State University (UNESP), Rio Claro, Brazil Department of Physiological Sciences, Federal University of São Carlos (UFSCAR), São Carlos, Brazil *Correspondence: [email protected] Edited by: Simon C. Gandevia, Neuroscience Research Australia, Australia INTRODUCTION proposed the existence of an individual this model proposes that there is always a exercise intensity beyond which there is no physiological reserve, both cardiovascular The maximal oxygen uptake (VO max) can be defined as the maximum integrated increase in the VO ,representing the limit and neuromuscular, once the number of of the cardiorespiratory capacity. However, motor unit recruited by the active muscles capacity of the pulmonary, cardiovascular the need for the plateau occurrence to during exercise is regulated by the brain and muscular systems to uptake, trans- the VO max determination presents lim- to prevent catastrophic failure in bodily port and utilize O , respectively (Poole 2 itations, once it conflicts with the fact that systems (Noakes and Marino, 2009). et al., 2008). Usually measured by the its occurrence is not universal (Doherty incremental exercise test in the tread- et al., 2003; Astorino et al., 2005). With the IS THE VO maxTHAT WEMEASURE mill or cycle ergometer, the VO max test purpose to solve this problem and ensure REALLY MAXIMAL? has become a cornerstone in clinical and that individuals attain always “maximal” applied physiology involving physical exer- Independently of the VO max conditions by the end of an incremental limiting/regulatory mechanisms (Ekblom, cise. Its applications are numerous, rang- exercise test, producing true VO max val- ing from elite athletes to individuals with 2 2009; Noakes and Marino, 2009), it several pathologic conditions (Mancini ues, the use of physiological parameters as is believed that implementing specific criteria for exercise test interruption based et al., 1991; Bassett and Howley, 2000). criteria during the incremental exercise upon respiratory exchange ratio, maximal Despite studied for approximately a cen- test as duration (Midgley et al., 2008), heart rate and blood lactate concentrations tury, questions regarding the VO max presence of the “verification phase” (Day became popular (Poole et al., 2008). These are still source of debate and disagree- et al., 2003; Midgley and Carroll, 2009), parameters, though, when used as criteria and rate of VO sample acquisition ment in the literature (Noakes, 1998; for VO max determination, can underesti- Bergh et al., 2000; Levine, 2008; Ekblom, (Astorino, 2009), one obtains true mate the actual measured value up to 26% VO max values. Two recent studies, 2009; Noakes and Marino, 2009; Spurway (Poole et al., 2008). Finally, the current et al., 2012). In particular, the study of however, challenge such beliefs. solution proposed to VO max determina- The first study (Mauger and the methods of VO max measurement 2 tion when the plateau does not occur, is the is a field of investigation that has been Sculthorpe, 2012)compared a conven- challenging through the years (Midgley use of the VO peak, which seems to be a tional incremental exercise test (i.e., with consistent VO max index, aslongasacon- et al., 2007, 2008). Intriguing findings 2 fixed load increments until voluntary stant supramaximal exercise test is done recently published (Beltrami et al., 2012; exhaustion) with a maximal self-paced after the incremental test, called “verifica- Mauger and Sculthorpe, 2012) bring addi- incremental exercise test regulated by tion phase” (Day et al., 2003; Midgley and tional debate regarding the measurement individual perception of effort. The Carroll, 2009). of the true VO max value and its limit- total duration of the latter was 10 min, Presently, two main theoretical mod- ing/regulatory mechanisms. In this article distributed in 5 stages of 2 min each, in els are discussed in the literature aiming which individuals controlled the exercise we briefly describe the current testing to explain the mechanisms of VO max methods and mechanisms of VO max lim- intensity at each moment in order to limitation and/or regulation. The classical achieve individual perceptions of effort itation/regulation, and discuss the new model proposes that VO max is limited by findings of these two recent studies and of 11, 13, 15, 17, and 20, respectively, in the maximal capacity of the heart to pro- the 15-points Borg scale. Interestingly, their possible implications in the field. vide O to the muscles, that means, when 2 this maximal self-paced incremental test one reaches the VO max the cardiovascu- resulted in a significantly higher VO max CURRENT MEASUREMENT AND lar system is working on its limit (Ekblom, (≈ 8%; Figure 1A)whencompared to VO max LIMITING/REGULATORY 2009). Alternatively, the other model advo- the values found during the conventional MECHANISMS cates that the cardiovascular system never incremental exercise test (Mauger and One of the most popular concepts used reaches a limit of work, and that VO max Sculthorpe, 2012). to obtain VO max during an incremental is regulated, rather than limited, by the The second study (Beltrami et al., 2012) exercise test is the occurrence of the number of motor unit recruited in the compared a conventional incremental plateau. The origin of this concept had exercising limbs, which is always submax- exercise test with a decremental protocol its basis in the studies of Hill and imal (Noakes and Marino, 2009). Thus, Lupton (1923) 90 years ago, in which they (i.e., with decreasing exercise intensity www.frontiersin.org August 2013 | Volume 4 | Article 203 | 1 Smirmaul et al. Is VO max really maximal? FIGURE 1 | (A) VO and power output data for the self-paced for the decremental protocol (right) in a representative subject. A incremental protocol (top) and conventional incremental protocol higher VO max (group mean ≈ 4.4%) was achieved in the (bottom) in a representative subject. A higher VO max (group decremental protocol during submaximal workload. VO is 2 2 mean ≈ 8%) was achieved in the self-paced incremental protocol represented by solid lines, and dotted lines represent speed. during submaximal workload. (B) VO and speed data for the “Reproduced from Mauger and Sculthorpe (2012) and Beltrami conventional incremental test (left) + verification phase (middle) and et al. (2012) with permission from BMJ Publishing Group Ltd.” levels over time). This decremental pro- reduction in the anaerobic component of values found (Beltrami et al., 2012; tocol started in the speed used during the the test, and/or an increase in the oxy- Mauger and Sculthorpe, 2012)uponthe “verification phase” of the incremental gen demand and utilization due to the existing body of knowledge relating to −1 test, which means, 1 km h faster than high power output in the last stage of this area? In our opinion, a consider- the last stage accomplished during the the self-paced incremental test, may also able portion of the scientific knowledge conventional exercise test. This intensity have contributed to the greater VO max would be mildly affected, due to the exis- was kept for 60% of the individual time found (Mauger and Sculthorpe, 2012). It tence of systematic error. For instance, that subjects were able to tolerate during is noteworthy that criticisms have already studies aiming to verify the effect of spe- the “verification phase,” with a subsequent been raised to this study (Chidnok et al., cific interventions upon VO max already −1 reduction in speed of 1 km h for 30 s 2013). At thesametime the authors of have VO max underestimations aggre- −1 and consecutive reductions of 0.5 km h , the second study (Beltrami et al., 2012) gated into their results. As pre- and post- in which each stage was kept for 30, 45, suggest that differences in the anticipa- intervention values are measured by the 60, 90, and 120 s, respectively. Similarly tory workload perception of the protocols, same protocol, the intervention effects to the maximal self-paced incremental growing in the conventional incremen- upon VO max values would still be cor- test (Mauger and Sculthorpe, 2012), the tal test and reducing in the decremental rectly measured, despite underestimation decremental test proposed resulted in test, might have impacted the sympathetic of VO max true value. In contrast, studies significantly higher VO max (≈ 4.4%; or parasympathetic drives and led to based upon VO max percentages, as the 2 2 Figure 1B) when compared to the conven- different metabolic responses to exercise aerobic training zone for cardiorespira- tional incremental exercise test (Beltrami and to the greater VO max. Surprisingly, tory fitness, for example, which habitually et al., 2012). both studies showed that either untrained varies around 50 and 85% of VO max, The main explanation suggested by (Mauger and Sculthorpe, 2012), or trained would have its interval range shifted to the authors for the results found in (Beltrami et al., 2012) individuals attained the right. Likewise, it would be neces- the first study (Mauger and Sculthorpe, the greater VO max values during sub- sary to review the indirect equations 2012) is that the nature of the self- maximal workloads, challenging the tradi- to estimate VO max, as they make use paced protocol may have allowed a higher tional concept that VO max occurs at the of VO max reference values that are, 2 2 power output for the same level of per- maximal workload. according to the new findings (Beltrami ception of effort or discomfort, lead- et al., 2012; Mauger and Sculthorpe, ing to greater VO max before voluntary IMPLICATIONS OF THE NEW FINDINGS 2012), submaximal. Nevertheless, know- exhaustion. This occurred despite heart ing the underestimation magnitude of Once recognized and further corrobo- rate, ventilation, and respiratory exchange rated that current VO max measurement the VO max by the conventional incre- 2 2 ratiovalues being similar tothe conven- methods (i.e., conventional incremental mental protocols, mathematical equations tional protocol. Additional suggestions as would be able to provide a posteriori exercise protocol) provide, in fact, a greater relative contribution of oxygen- submaximal values, which would be the corrections, reducing/correcting such dependent type 1 fibers with a consequent inaccuracies. implications of the new true VO max Frontiers in Physiology | Exercise Physiology August 2013 | Volume 4 | Article 203 | 2 Smirmaul et al. Is VO max really maximal? Contrary to the relatively minor impact emphasizes the paramount importance of determinants of endurance performance. Med. Sci. Sports Exerc. 32, 70–84. described above, the findings of greater effort on endurance exercise performance Beltrami,F.G., Froyd, C.,Mauger, A. R.,Metcalfe, VO max than the ones commonly found regulation and tolerance (Marcora and A. J., Marino, F., and Noakes, T. D. (2012). during conventional incremental exercise Staiano, 2010; Smirmaul et al., 2013). The Conventional testing methods produce submaxi- tests conflict with the theoretical models higher VO max values achieved (Beltrami 2 mal values of maximum oxygen consumption. Br. proposed to explain its limiting/regulatory et al., 2012; Mauger and Sculthorpe, 2012) J. Sports Med. 46, 23–29. doi: 10.1136/bjsports- 2011-090306 mechanisms (Ekblom, 2009; Noakes and may have been associated with altered per- Bergh, U., Ekblom, B., and Astrand, P. O. (2000). Marino, 2009). If the VO max values ceptual responses due to the differences in Maximal oxygen uptake “classical” versus “con- found so far during conventional incre- the protocols used. However, this possibil- temporary” viewpoints. Med. Sci. Sports Exerc. 32, mental tests are limited by the maximal ity remains speculative. 85–88. Billat, V., Petot, H., Karp,J.R., Sarre, G.,Morton, capacity of the heart to provide O to R. H., and Mille-Hamard, L. (2013). The sus- CONCLUSION the muscles (Ekblom, 2009), how can one tainability of VO2max: effect of decreasing the The proposals of different exercise proto- explain such an increase (Beltrami et al., workload. Eur. J. Appl. Physiol. 113, 385–394. doi: cols which result in greater VO max values 2012; Mauger and Sculthorpe, 2012)? We 2 10.1007/s00421-012-2424-7 than commonly found during the con- identify two possibilities. The theoretical Chidnok, W., Dimenna, F. J., Bailey, S. J., Burnley, M., Wilkerson, D. P., Vanhatalo, A., et al. (2013). ventional incremental exercise tests should model may still be correct, that means, VO2max is not altered by self-pacing during incre- interest the exercise and sports physiol- VO max is indeed limited by the maximal mental exercise: reply to the letter of Alexis, R. ogy community. At the same time that capacity of the heart, though, the VO max Mauger. Eur. J. Appl. Physiol. 113, 543–544. doi: such findings mildly impact a consid- values found during conventional incre- 10.1007/s00421-012-2563-x mental tests are not truly maximal, and erable portion of knowledge, they chal- Day, J. R., Rossiter, H. B.,Coats, E.M., Skasick, A.,and Whipp, B. J. (2003). The maximally attainable VO2 lenge, for instance, the theoretical models alternative protocols would be able to during exercise in humans: the peak vs. maximum increase it. In opposition, the model may to explain VO max limitation/regulation. issue. J. Appl. Physiol. 95, 1901–1907. Still, they also challenge the concept that be wrong in stating that VO max is pri- Doherty, M., Nobbs, L., and Noakes, T. D. (2003). marily limited by the cardiac capacity, VO max occurs at the maximal work- Low frequency of the “plateau phenomenon” dur- load. While recent work has shown that ing maximal exercise in elite British athletes. Eur. and another mechanism might exist to J. Appl. Physiol. 89, 619–623. doi: 10.1007/s00421- it is possible to maintain a conventional explain its limitation/regulation. The other 003-0845-z VO max plateau up to 15 min by decreas- theoretical model (Noakes and Marino, 2 Ekblom, B. (2009). Counterpoint: maximal oxygen ing individuals’ workload, that means, 2009), on its turn, also conflicts with the uptake is not limited by a central nervous system during submaximal work (Petot et al., findings. If the brain regulates the num- governor. J. Appl. Physiol. 106, 339–341. discus- 2012; Billat et al., 2013), it is unknown sion: 341–342. ber of motor unit recruited during exer- Hill, A. V., and Lupton, H. (1923). Muscular exer- whether the same is possible for the cise in order to prevent catastrophic fail- cise, lactic acid, and the supply and utiliza- superior VO max values found (Beltrami ure in bodily systems, thus regulating the tion of oxygen. Q. J. Med. 16, 135–171. doi: VO max achievable, why would the brain et al., 2012; Mauger and Sculthorpe, 2012). 10.1093/qjmed/os-16.62.135 The suggestion that VO max values are allow individuals during these two new 2 Jones, N. L., and Killian, K. J. (2000). Exercise limi- tation in health and disease. N. Engl. J. Med. 343, protocols (Beltrami et al., 2012; Mauger task-dependent, and that the conventional 632–641. doi: 10.1056/NEJM200008313430907 incremental exercise test does not produce and Sculthorpe, 2012) to attain VO max Levine, B. D. (2008). VO2max: what do we true maximal values is attractive. However, values greater than during the conven- know, and what do we still need to know. understanding how these new exercise tional incremental tests? Would not the J. Physiol. 586, 25–34. doi: 10.1113/jphysiol.2007. protocols produce higher VO max values, brain, based on afferent feedback from 147629 Mancini, D. M., Eisen, H., Kussmaul, W., Mull, R., the influences of different protocols on various systems, regulate the number of Edmunds, L. H., and Wilson, J. R. (1991). Value perceptual responses and VO max mea- motor unit recruited in a similar fash- of peak exercise oxygen consumption for opti- surement, determining its full implications ion, independently of the exercise protocol mal timing of cardiac transplantation in ambu- and applications, and the specific limit- performed? latory patients with heart failure. Circulation 83, A possible explanation for the recent ing/regulatory mechanisms underpinning 778–786. doi: 10.1161/01.CIR.83.3.778 Marcora, S. M., and Staiano, W. (2010). The limit VO max, are new horizons that sports and findings may be found reaching back 2 to exercise tolerance in humans: mind over mus- exercise scientists may explore. to the proposal by Jones and Killian cle. Eur. J. Appl. Physiol. 109, 763–770. doi: (2000), who reviewed evidence to show 10.1007/s00421-010-1418-6 that, rather than limitations based on the Mauger, A. R., and Sculthorpe, N. (2012). A REFERENCES Astorino, T. A. (2009). Alterations in VOmax and new VO2max protocol allowing self-pacing capacity of oxygen-delivery mechanisms, in maximal incremental exercise. Br.J.Sports the VO plateau with manipulation of sampling cardiorespiratory and exercise limitations interval. Clin. Physiol. Funct. Imaging 29, 60–67. Med. 46, 59–63. doi: 10.1136/bjsports-2011- are symptom-based. 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