title: Non-invasive evaluation of the capillary recruitment in the human muscle during exercise in hypoxia.
abstract: This study proposes a non-invasive evaluation of capillary recruitment in human muscle from resting state to maximal exercise while under hypoxic conditions. Our work is based on the analysis of oxygen transport variables measured during incremental exercise in endurance-trained men (n=8) and in their sedentary counterparts (n=8). Maximal exercise tests were performed on a cycloergometer in normoxia and at three simulated normobaric levels of hypoxia (altitude equivalent to 1000, 2500 and 4500 m). We made the assumption that the relationship between the oxygen diffusion coefficient (Kt) and cardiac output (Qc) was: Kt=kQcNc where Nc is the capillary recruitment coefficient during exercise. Our results demonstrate that Nc increases with altitude and that the increase is greater in trained compared with untrained subjects at high altitude (4500 m). Moreover, the venous PO2 threshold beyond which capillary recruitment increases is lower in trained men. Despite their greater increase in capillary recruitment, trained men are not able to compensate for their drastic drop in arterial oxygen content during exercise in acute hypoxia, which results in a greater drop in maximal oxygen consumption than in sedentary men.
authors.affiliation: Université Paris 13, Laboratoire Réponses cellulaires et fonctionnelles à l'hypoxie, EA 2363, and AP-HP Hôpital AVicenne, Service de Physiologie, Explorations Fonctionnelles et Médecine du sport, Bobigny, France. nicolas.bourdillon@gmail.com
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bourdillon
authors.forename: Pascal
authors.initials: P
authors.lastname: Mollard
authors.forename: Murielle
authors.initials: M
authors.lastname: Letournel
authors.forename: Michèle
authors.initials: M
authors.lastname: Beaudry
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Richalet
mesh_terms: D000328:Adult; D002196:Capillaries / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D013177:Sports / Q000502:physiology; D055815:Young Adult