Rebuttal from Drs. Noakes and Marino

Abstract

POINT-COUNTERPOINTRebuttal from Drs. Noakes and MarinoPublished Online:01 Jan 2009https://doi.org/10.1152/japplphysiol.90844.2008bMoreSectionsPDF (37 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat According to Dr. Ekblom we have yet to produce practical evidence for the existence of a central governor. In our exchange we provided examples of substantial evidence for the central governor model (CGM). We suggest that those who wish to disprove a theory need to interpret their data without the bias introduced by long held preconceptions. We contend that Dr. Ekblom and colleagues have provided irrefutable evidence that the magnitude of the V̇o2max in combined arm and leg exercise (cA+L) is determined by the mass of muscle that the brain is prepared to recruit during such exercise (1, 2).Dr. Ekblom interprets the EMG evidence (1) as disproof of the CGM since EMG activity increased when V̇o2max remained unchanged” during supramaximal exercise at a fixed work rate. Apparently, the CGM is refuted by adding V̇o2max values obtained during separate maximal tests for arm (3.32 l/min) and leg cycling (4.46 l/min) and arriving at a combined V̇o2max of 7.78 l/min which was ∼40% higher than the actual V̇o2max (∼4.55 l/min) obtained during cA+L (1). The authors concluded that the heart was unable to provide a sufficiently large cardiac output to perfuse this greater muscle mass. Surprisingly this same logic is not used to interpret the EMG data since the authors measured the EMG activity only during cA+L exercise and not during exercise with arms or legs alone. Thus they had to assume that the same number of motor units were recruited during maximal exercise with arms and legs whether the individual limbs exercise either alone or in combination. But we already know that this is not the case (6).They had therefore to speculate that exercise with the arms (or legs) alone might (current authors' emphasis) have been maximal (i.e., all motor units were activated) although the heart rates were submaximal and the “plateau phenomenon” was absent at exercise termination during arm exercise. In contrast to this speculation, active muscle recruitment in both the arms and legs was clearly submaximal during “maximal” cA+L tests since “maximal” exercise terminated when EMG activities in the vastus lateralis and triceps brachii muscles were only 38–50% and 24–44% of activities measured during maximal voluntary contractions of those respective muscle groups (Table 2 p. 607 in Ref. 2).We repeatedly argued that submaximal muscle activation in the exercising limbs at exhaustion must indicate that the exercise is centrally regulated since we can think of no other logical explanation (3–5).REFERENCES1 Brink-Elfegoun T, Holmberg HC, Nordland Ekblom M, Ekblom B. Neuromuscular and circulatory adaptation during combined arm and leg exercise with different maximal work loads. Eur J Appl Physiol 101: 603–611, 2007.Crossref | ISI | Google Scholar2 Brink-Elfegoun T, Kaijser L, Gustafsson T, Ekblom B. Maximal oxygen uptake is not limited by a central nervous system governor. J Appl Physiol 102: 781–786, 2007.Link | ISI | Google Scholar3 Noakes TD. Maximal oxygen uptake as a parametric measure of cardiorespiratory capacity: Comment. Med Sci Sports Exerc 40: 585, 2008.Crossref | ISI | Google Scholar4 Noakes TD. Testing for maximum oxygen consumption has produced a brainless model of human exercise performance. Br J Sports Med 42: 551–555, 2008.Crossref | ISI | Google Scholar5 Noakes TD, St Clair Gibson A. Logical limitations to the “catastrophe” models of fatigue during exercise in humans. Br J Sports Med 38: 648–649, 2004.Crossref | ISI | Google Scholar6 Vandervoort AA, Sale DG, Moroz J. Comparison of motor unit activation during unilateral and bilateral leg extension. J Appl Physiol 56: 46–51, 1984.Link | ISI | Google Scholar Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 106Issue 1January 2009Pages 341-341 Copyright & PermissionsCopyright © 2009 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.90844.2008bHistory Published online 1 January 2009 Published in print 1 January 2009 Metrics