VO2max: what do we know, and what do we still need to know? J Physiol

Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, 7232 Greenville Avenue, Dallas, TX 75231, USA.
The Journal of Physiology (Impact Factor: 5.04). 02/2008; 586(1):25-34. DOI: 10.1113/jphysiol.2007.147629
Source: PubMed


Maximal oxygen uptake (.VO(2,max)) is a physiological characteristic bounded by the parametric limits of the Fick equation: (left ventricular (LV) end-diastolic volume--LV end-systolic volume) x heart rate x arterio-venous oxygen difference. 'Classical' views of .VO(2,max) emphasize its critical dependence on convective oxygen transport to working skeletal muscle, and recent data are dispositive, proving convincingly that such limits must and do exist. 'Contemporary' investigations into the mechanisms underlying peripheral muscle fatigue due to energetic supply/demand mismatch are clarifying the local mediators of fatigue at the skeletal muscle level, though the afferent signalling pathways that communicate these environmental conditions to the brain and the sites of central integration of cardiovascular and neuromotor control are still being worked out. Elite endurance athletes have a high .VO(2,max) due primarily to a high cardiac output from a large compliant cardiac chamber (including the myocardium and pericardium) which relaxes quickly and fills to a large end-diastolic volume. This large capacity for LV filling and ejection allows preservation of blood pressure during extraordinary rates of muscle blood flow and oxygen transport which support high rates of sustained oxidative metabolism. The magnitude and mechanisms of cardiac phenotype plasticity remain uncertain and probably involve underlying genetic factors, as well as the length, duration, type, intensity and age of initiation of the training stimulus.

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    • "For endurance athletes, maximal oxygen consumption allows a more appropriate and objective classification, because this variable is considered " gold-standard " and predicts time-trial performance [22]. This is due to the concept that an athlete's maximal oxygen consumption is mainly determined by the oxygen delivery to the mitochondria and its utilization, which in turn are limiting the oxidative production of ATP required for the energy supply of the working muscles [23]. As neural efficiency is task-related, it is necessary to study brain cortical activity in athletes directly during endurance exercise. "

    Neural Plasticity 10/2015; · 3.60 Impact Factor
    • "Variables significantly associated with VO 2peak in bivariate analysis were entered into the regression model as independent variables. Additionally, multiple regression analyses forcing the inclusion of potential causative variables (Q peak , haemotological variables, capillary-to-fibre ratio, total Mito VD , ST cross-sectional area) based on established underlying physiology (di Prampero & Ferretti, 1990; Bassett & Howley, 2000; Levine, 2008 "
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    ABSTRACT: It remains unclear whether improvements in peak oxygen uptake (VO2peak ) following endurance training (ET) are primarily determined by central and/or peripheral adaptations. Herein, we tested the hypothesis that the improvement in VO2peak following 6 weeks of ET is mainly determined by haematological rather than skeletal muscle adaptations. Sixteen untrained healthy male volunteers (age = 25 ± 4 years, VO2peak = 3.5 ± 0.5 l min(-1) ) underwent supervised ET (6 weeks, 3-4 sessions/week). VO2peak , peak cardiac output (Qpeak ), haemoglobin mass (Hbmass ) and blood volumes were assessed prior to and following ET. Skeletal muscle biopsies were analysed for mitochondrial volume density (MitoVD ), capillarity, fibre types and respiratory capacity (OXPHOS). After the post ET assessment, red blood cell volume (RBCV) was re-established to the pre ET level by phlebotomy and VO2peak and Qpeak were measured again. We speculated that the contribution of skeletal muscle adaptations to the ET-induced increase in VO2peak would be revealed when controlling for haematological adaptations. VO2peak and Qpeak were increased (P < 0.05) following ET (9 ± 8 and 7 ± 6 %, respectively) and decreased (P < 0.05) after phlebotomy (-7 ± 7 and -10 ± 7 %). RBCV, plasma volume and Hbmass all increased (P < 0.05) after ET (8 ± 4, 4 ± 6 and 6 ± 5 %). As for skeletal muscle adaptations, capillary-to-fibre ratio and total MitoVD increased (P < 0.05) following ET (18 ± 16 and 43 ± 30 %), but OXPHOS remained unaltered. Through stepwise multiple regression analysis, Qpeak , RBCV and Hbmass were independent predictors of VO2peak . In conclusion, the improvement in VO2peak following 6 weeks of ET is primarily attributed to increases in Qpeak and oxygen-carrying capacity of blood in untrained healthy young subjects. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    The Journal of Physiology 08/2015; 593(20). DOI:10.1113/JP270250 · 5.04 Impact Factor
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    • "In fact, several current models suggest that the rating of perceived exertion (RPE) is of critical importance in dictating central motor drive, and ultimately mechanical output (Noakes, 2004b; Tucker and Noakes, 2009; Marcora and Staiano, 2010). However, despite increasing support for the role of RPE [also referred to by some as the sense of effort or perception of effort (Amann et al., 2007; Dempsey et al., 2008; Marcora, 2009a)] in regulating exercise performance (Edwards, 1983; Bassett and Howley, 2000; Noakes and St. Clair Gibson, 2004; St. Clair Gibson et al., 2006; Levine, 2007; Crewe et al., 2008; Joseph et al., 2008; Tucker, 2009; Amann, 2011; Girard et al., 2011), it is still debated whether this perception or sense is generated via the feedback of afferent sensory receptors stimulated in response to fatiguing locomotor muscles and other organs, and/or is a centrally-originating signal, and whether it acts on the CNS at conscious or sub-conscious levels (Bainbridge, 1919; Marcora, 2009a,b, 2010; Meeusen et al., 2009; Amann and Secher, 2010; Perrey et al., 2010). Much of the debate over the origin of this sensation of fatigue may be attributed to a too-broad operational definition of the RPE, the interchangeable use of the terms " effort " and " exertion , " inconsistent instructions provided by the researchers to the subjects on how to rate one's own perceived exertion and the selective interpretation of results that incorporate the rating (Noakes, 2004a; Lambert, 2005; Meeusen et al., 2009; Tucker, 2009; de Morree and Marcora, 2010; Lane et al., 2011; Swart et al., 2011; Smirmaul, 2012). "
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    ABSTRACT: Purpose: We explored the effects of the sense of effort and accompanying perceptions of peripheral discomfort on self-selected cycle power output under two different inspired O2 fractions. Methods: On separate days, eight trained males cycled for 5 min at a constant subjective effort (sense of effort of '3' on a modified Borg CR10 scale), immediately followed by five 4-s progressive submaximal (sense of effort of "4, 5, 6, 7, and 8"; 40 s between bouts) and two 4-s maximal (sense of effort of "10"; 3 min between bouts) bouts under normoxia (NM: fraction of inspired O2 [FiO2] 0.21) and hypoxia (HY: [FiO2] 0.13). Physiological (Heart Rate, arterial oxygen saturation (SpO2) and quadriceps Root Mean Square (RMS) electromyographical activity) and perceptual responses (overall peripheral discomfort, difficulty breathing and limb discomfort) were recorded. Results: Power output and normalized quadriceps RMS activity were not different between conditions during any exercise bout (p > 0.05) and remained unchanged across time during the constant-effort cycling. SpO2 was lower, while heart rate and ratings of perceived difficulty breathing were higher under HY, compared to NM, at all time points (p < 0.05). During the constant-effort cycling, heart rate, overall perceived discomfort, difficulty breathing and limb discomfort increased with time (all p < 0.05). All variables (except SpO2) increased along with sense of effort during the brief progressive cycling bouts (all p < 0.05). During the two maximal cycling bouts, ratings of overall peripheral discomfort displayed an interaction between time and condition with ratings higher in the second bout under HY vs. NM conditions. During self-selected, constant-effort and brief progressive, sub-maximal, and maximal cycling bouts, mechanical work is regulated in parallel to the sense of effort, independently from peripheral sensations of discomfort.
    Frontiers in Physiology 03/2014; 5:115. DOI:10.3389/fphys.2014.00115 · 3.53 Impact Factor
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