title: Does oxidative capacity affect energy cost? An in vivo MR investigation of skeletal muscle energetics.
abstract: Investigations of training effects on exercise energy cost have yielded conflicting results. The purpose of the present study was to compare quadriceps energy cost and oxidative capacity between endurance-trained and sedentary subjects during a heavy dynamic knee extension exercise. We quantified the rates of ATP turnover from oxidative and anaerobic pathways with (31)P-MRS, and we measured simultaneously pulmonary oxygen uptake in order to assess both total ATP production [i.e., energy cost (EC)] and O(2) consumption (O(2) cost) scaled to power output. Seven sedentary (SED) and seven endurance-trained (TRA) subjects performed a dynamic standardized rest-exercise-recovery protocol at an exercise intensity corresponding to 35% of maximal voluntary contraction. We showed that during a dynamic heavy exercise, the O(2) cost and EC were similar in the SED and endurance-trained groups. For a given EC, endurance-trained subjects exhibited a higher relative mitochondrial contribution to ATP production at the muscle level (84 +/- 12% in TRA and 57 +/- 12% in SED; P < 0.01) whereas the anaerobic contribution was reduced (18 +/- 12% in TRA and 44 +/- 11% in SED; P < 0.01). Our results obtained in vivo illustrate that on the one hand the beneficial effects of endurance training are not related to any reduction in EC or O(2) cost and on the other hand that this similar EC was linked to a change regarding the contribution of anaerobic and oxidative processes to energy production, i.e., a greater aerobic energy contribution associated with a concomitant reduction of the anaerobic energy supply.
authors.affiliation: Centre de Resonance Magnetique Biologique et Medicale, Faculté de Médecine de Marseille, UMR CNRS 6612, 27 Bd Jean Moulin, 13005, Marseille, France.
authors.forename: Gwenael
authors.initials: G
authors.lastname: Layec
authors.forename: Aurélien
authors.initials: A
authors.lastname: Bringard
authors.forename: Christophe
authors.initials: C
authors.lastname: Vilmen
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Micallef
authors.forename: Yann
authors.initials: Y
authors.lastname: Le Fur
authors.forename: Stéphane
authors.initials: S
authors.lastname: Perrey
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Cozzone
authors.forename: David
authors.initials: D
authors.lastname: Bendahan
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D000693:Anaerobiosis / Q000502:physiology; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology
chemical_list: D000255:Adenosine Triphosphate