title: Phlebotomy eliminates the maximal cardiac output response to six weeks of exercise training.
abstract: With this study we tested the hypothesis that 6 wk of endurance training increases maximal cardiac output (Qmax) relatively more by elevating blood volume (BV) than by inducing structural and functional changes within the heart. Nine healthy but untrained volunteers (Vo2max 47 ± 5 ml·min(-1)·kg(-1)) underwent supervised training (60 min; 4 times weekly at 65% Vo2max for 6 wk), and Qmax was determined by inert gas rebreathing during cycle ergometer exercise before and after the training period. After the training period, blood volume (determined in duplicates by CO rebreathing) was reestablished to pretraining values by phlebotomy and Qmax was quantified again. Resting echography revealed no structural heart adaptations as a consequence of the training intervention. After the training period, plasma volume (PV), red blood cell volume (RBCV), and BV increased (P < 0.05) by 147 ± 168 (5 ± 5%), 235 ± 64 (10 ± 3%), and 382 ± 204 ml (7 ± 4%), respectively. Vo2max was augmented (P < 0.05) by 10 ± 7% after the training period and decreased (P < 0.05) by 8 ± 7% with phlebotomy. Concomitantly, Qmax was increased (P < 0.05) from 18.9 ± 2.1 to 20.4 ± 2.3 l/min (9 ± 6%) as a consequence of the training intervention, and after normalization of BV by phlebotomy Qmax returned to pretraining values (18.1 ± 2.5 l/min; 12 ± 5% reversal). Thus the exercise training-induced increase in BV is the main mechanism increasing Qmax after 6 wk of endurance training in previously untrained subjects.
authors.affiliation: Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark;
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Bonne
authors.affiliation: Laboratoire Performance et Santé en Altitude, Université de Perpignan, Font-Romeu, France;
authors.forename: Gregory
authors.initials: G
authors.lastname: Doucende
authors.affiliation: Zürich Center for Integrative Human Physiology (ZIHP), University of Zürich, Zürich, Switzerland;
authors.forename: Daniela
authors.initials: D
authors.lastname: Flück
authors.affiliation: Zürich Center for Integrative Human Physiology (ZIHP), University of Zürich, Zürich, Switzerland;
authors.forename: Robert A
authors.initials: RA
authors.lastname: Jacobs
authors.affiliation: Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark;
authors.forename: Nikolai B
authors.initials: NB
authors.lastname: Nordsborg
authors.affiliation: Ecole Nationale des Sports de Montagne, site de l'Ecole Nationale de Ski et d'Alpinisme, Chamonix, France;
authors.forename: Paul
authors.initials: P
authors.lastname: Robach
authors.affiliation: Laboratoire de Pharm-Ecologie Cardiovasculaire, Université d'Avignon, Avignon, France;
authors.forename: Guillaume
authors.initials: G
authors.lastname: Walther
authors.affiliation: Zürich Center for Integrative Human Physiology (ZIHP), University of Zürich, Zürich, Switzerland; Food & Nutrition & Sport Science, Gothenburg University, Sweden carsten.lundby@access.uzh.ch.
authors.forename: Carsten
authors.initials: C
authors.lastname: Lundby
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D001810:Blood Volume / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D006321:Heart / Q000033:anatomy & histology / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D018962:Phlebotomy; D010807:Physical Endurance / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology; D013997:Time Factors
keywords: Q; adaptations; blood; cardiac output; training