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

ABSTRACT 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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    • "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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    • "[5]. This is highlighted in endurance-trained athletes, where O2 transport is the most important limiting factor of "
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    ABSTRACT: The ability of the cardiorespiratory system (heart, lungs, blood) to deliver oxygen to exercising skeletal muscle constrains maximum oxygen consumption V˙O2max, with cardiac output and the concentration of oxygen-carrying haemoglobin ([Hb]) being key limiting parameters. Total blood volume (BV) is the sum of the plasma volume (PV) and the total red cell volume. The measured [Hb] is dependent upon the total circulating mass of haemoglobin (tHb-mass) and plasma volume (PV). While the proportion of oxygen carried in plasma is trivial (0.3 mL of oxygen per 100 mL of plasma), each gram of Hb, contained in red blood cells, binds 1.39 mL of oxygen. As a result, the relationship between V˙O2max and tHb-mass is stronger than that observed between V˙O2max and [Hb] or BV. The glycoprotein hormone erythropoietin drives red cell synthesis and, like simple transfusion of packed red blood cells, can increase tHb-mass. An iron-containing haem group lies at the centre of the Hb molecule and, in situations of actual or functional iron deficiency, tHb-mass will also rise following iron administration. However achieved, an increase in tHb-mass also increases circulating oxygen-carrying capacity, and thus the capacity for aerobic phosphorylation. It is for such reasons that alterations in V˙O2max and exercise performance are proportional to those in arterial oxygen content and systemic oxygen transport, a change in tHb-mass of 1 g being associated with a 4 mL · min-1 change in V˙O2max. Similarly, V˙O2max increases by approximately 1% for each 3 g · L-1 increase in [Hb] over the [Hb] range (120 to 170 g · L-1). Surgery, like exercise, places substantial metabolic demands on the patient. Whilst subject to debate, oxygen supply at a rate inadequate to prevent muscle anaerobiosis may underpin the occurrence of the anaerobic threshold (AT), an important submaximal marker of cardiorespiratory fitness. Preoperatively, cardiopulmonary exercise testing (CPET) can be used to determine AT and peak exertional oxygen uptake (V˙O2 peak) as measures of ability to meet increasing oxygen demands. The degree of surgical insult and the ability to meet the resulting additional postoperative oxygen demand appear to be fundamental determinants of surgical outcome: individuals in whom such ability is impaired (and thus those with reduced V˙O2 peak and AT) are at greater risk of adverse surgical outcome. This review provides an overview of the relationships between [Hb], tHb-mass, exercise capacity, and surgical outcome and discusses the potential value of assessing tHb-mass over [Hb].
    11/2013; 2(1):33. DOI:10.1186/2046-7648-2-33
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    • "and is one of the major characteristics that determine endurance performance (di Prampero, 2003; Levine, 2008). Importantly, the highest VO2max value does not necessarily equate to the best endurance performance, but the best endurance performance typically demands high VO2max values (Saltin & Åstrand, 1967; Costill et al., 1973; Lucia et al., 1998; Bassett & Howley, 2000; Impellizzeri et al., 2005). "
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    ABSTRACT: Here we report on the effect of combining endurance training with heavy or explosive strength training on endurance performance in endurance-trained runners and cyclists. Running economy is improved by performing combined endurance training with either heavy or explosive strength training. However, heavy strength training is recommended for improving cycling economy. Equivocal findings exist regarding the effects on power output or velocity at the lactate threshold. Concurrent endurance and heavy strength training can increase running speed and power output at VO2max (Vmax and Wmax , respectively) or time to exhaustion at Vmax and Wmax . Combining endurance training with either explosive or heavy strength training can improve running performance, while there is most compelling evidence of an additive effect on cycling performance when heavy strength training is used. It is suggested that the improved endurance performance may relate to delayed activation of less efficient type II fibers, improved neuromuscular efficiency, conversion of fast-twitch type IIX fibers into more fatigue-resistant type IIA fibers, or improved musculo-tendinous stiffness.
    Scandinavian Journal of Medicine and Science in Sports 08/2013; 4(4). DOI:10.1111/sms.12104 · 2.90 Impact Factor
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