title: Mechanisms responsible for the acceleration of pulmonary V̇O2 on-kinetics in humans after prolonged endurance training.
abstract: The effect of prolonged endurance training on the pulmonary V̇O2 on- and off-kinetics in humans, in relation to muscle mitochondria biogenesis, is investigated. Eleven untrained physically active men (means±SD: age 22.4±1.5 years, V̇O2peak 3,187±479 ml/min) performed endurance cycling training (4 sessions per week) lasting 20 wk. Training shortened τp of the pulmonary V̇O2 on-kinetics during moderate-intensity cycling by ∼19% from 28.3±5.2 to 23.0±4.0 s (P=0.005). τp of the pulmonary V̇O2 off-kinetics decreased by ∼11% from 33.7±7.2 to 30.0±6.6 (P=0.02). Training increased (in vastus lateralis muscle) mitochondrial DNA copy number in relation to nuclear DNA (mtDNA/nDNA) (+53%) (P=0.014), maximal citrate synthase (CS) activity (+38%), and CS protein content (+38%) (P=0.004), whereas maximal cytochrome c oxidase (COX) activity after training tended to be only slightly (+5%) elevated (P=0.08). By applying to the experimental data, our computer model of oxidative phosphorylation (OXPHOS) and using metabolic control analysis, we argue that COX activity is a much better measure of OXPHOS intensity than CS activity. According to the model, in the present study a training-induced increase in OXPHOS activity accounted for about 0-10% of the decrease in τp of muscle and pulmonary V̇O2 for the on-transient, whereas the remaining 90-100% is caused by an increase in each-step parallel activation of OXPHOS.
authors.affiliation: Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Kraków, Poland; jerzy.zoladz@awf.krakow.pl.
authors.forename: Jerzy A
authors.initials: JA
authors.lastname: Zoladz
authors.affiliation: Dipartimento di Scienze Mediche e Biologiche, Università degli Studi di Udine, Udine, Italy;
authors.forename: Bruno
authors.initials: B
authors.lastname: Grassi
authors.affiliation: Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Kraków, Poland;
authors.forename: Joanna
authors.initials: J
authors.lastname: Majerczak
authors.affiliation: Faculty of Applied Mathematics, AGH-UST, Kraków, Poland;
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Szkutnik
authors.affiliation: Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland;
authors.forename: Michal
authors.initials: M
authors.lastname: Korostyński
authors.affiliation: Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Kraków, Poland;
authors.forename: Marcin
authors.initials: M
authors.lastname: Grandys
authors.affiliation: Department of Bioenergetics, Adam Mickiewicz University, Poznan, Poland; and.
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Jarmuszkiewicz
authors.affiliation: Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland.
authors.forename: Bernard
authors.initials: B
authors.lastname: Korzeniewski
mesh_terms: D003198:Computer Simulation; D004272:DNA, Mitochondrial / Q000378:metabolism; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008168:Lung / Q000378:metabolism*; D008297:Male; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D055815:Young Adult
chemical_list: D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; D019344:Lactic Acid; D018995:Myosin Heavy Chains; D010100:Oxygen
keywords: COX activity; CS activity; cycling; endurance training; oxygen uptake kinetics