title: Exercise training in normobaric hypoxia in endurance runners. II. Improvement of mitochondrial properties in skeletal muscle.
abstract: This study investigates whether adaptations of mitochondrial function accompany the improvement of endurance performance capacity observed in well-trained athletes after an intermittent hypoxic training program. Fifteen endurance-trained athletes performed two weekly training sessions on treadmill at the velocity associated with the second ventilatory threshold (VT2) with inspired O2 fraction = 14.5% [hypoxic group (Hyp), n = 8] or with inspired O2 fraction = 21% [normoxic group (Nor), n = 7], integrated into their usual training, for 6 wk. Before and after training, oxygen uptake (VO2) and speed at VT2, maximal VO2 (VO2 max), and time to exhaustion at velocity of VO2 max (minimal speed associated with VO2 max) were measured, and muscle biopsies of vastus lateralis were harvested. Muscle oxidative capacities and sensitivity of mitochondrial respiration to ADP (Km) were evaluated on permeabilized muscle fibers. Time to exhaustion, VO2 at VT2, and VO2 max were significantly improved in Hyp (+42, +8, and +5%, respectively) but not in Nor. No increase in muscle oxidative capacity was obtained with either training protocol. However, mitochondrial regulation shifted to a more oxidative profile in Hyp only as shown by the increased Km for ADP (Nor: before 476 +/- 63, after 524 +/- 62 microM, not significant; Hyp: before 441 +/- 59, after 694 +/- 51 microM, P < 0.05). Thus including hypoxia sessions into the usual training of athletes qualitatively ameliorates mitochondrial function by increasing the respiratory control by creatine, providing a tighter integration between ATP demand and supply.
authors.affiliation: Service de Physiologie Clinique et des Explorations Fonctionnelles Respiratoires et de l'Exercice, Département de Physiologie, Equipe d'Accueil 3072, Strasbourg, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Ponsot
authors.forename: Stéphane P
authors.initials: SP
authors.lastname: Dufour
authors.forename: Joffrey
authors.initials: J
authors.lastname: Zoll
authors.forename: Stéphane
authors.initials: S
authors.lastname: Doutrelau
authors.forename: Benoit
authors.initials: B
authors.lastname: N'Guessan
authors.forename: Bernard
authors.initials: B
authors.lastname: Geny
authors.forename: Hans
authors.initials: H
authors.lastname: Hoppeler
authors.forename: Eliane
authors.initials: E
authors.lastname: Lampert
authors.forename: Bertrand
authors.initials: B
authors.lastname: Mettauer
authors.forename: Renée
authors.initials: R
authors.lastname: Ventura-Clapier
authors.forename: Ruddy
authors.initials: R
authors.lastname: Richard
mesh_terms: D000222:Adaptation, Physiological; D000244:Adenosine Diphosphate / Q000378:metabolism; D000328:Adult; D004734:Energy Metabolism; D017079:Exercise Tolerance / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D007700:Kinetics; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation; D012420:Running; D013178:Sports Medicine
chemical_list: D000244:Adenosine Diphosphate