title: Morphological adaptations of human skeletal muscle to chronic hypoxia.
abstract: Muscle structural changes during typical mountaineering expeditions to the Himalayas were assessed by taking muscle biopsies from 14 mountaineers before and after their sojourn at high altitude (greater than 5000 m for over 8 weeks). M. vastus lateralis samples were analyzed morphometrically from electron micrographs. A significant reduction (-10%) of muscle cross-sectional area was found on CT scans of the thigh. Morphologically this loss in muscle mass appeared as a decrease in muscle fiber size mainly due to a loss of myofibrillar proteins. A loss of muscle oxidative capacity was also evident, as indicated by a decrease in the volume of muscle mitochondria (-25%). In contrast, the capillary network was mostly spared from catabolism. It is therefore concluded that oxygen availability to muscle mitochondria after prolonged high-altitude exposure in humans is improved due to an unchanged capillary network, supplying a reduced muscle oxidative capacity.
authors.affiliation: Department of Anatomy, University of Berne, Switzerland.
authors.forename: H
authors.initials: H
authors.lastname: Hoppeler
authors.forename: E
authors.initials: E
authors.lastname: Kleinert
authors.forename: C
authors.initials: C
authors.lastname: Schlegel
authors.forename: H
authors.initials: H
authors.lastname: Claassen
authors.forename: H
authors.initials: H
authors.lastname: Howald
authors.forename: S R
authors.initials: SR
authors.lastname: Kayar
authors.forename: P
authors.initials: P
authors.lastname: Cerretelli
mesh_terms: D000064:Acclimatization / Q000502:physiology; D000328:Adult; D000531:Altitude; D001823:Body Composition; D002196:Capillaries / Q000033:anatomy & histology; D002908:Chronic Disease; D006801:Humans; D000860:Hypoxia / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D009051:Mountaineering; D009132:Muscles / Q000098:blood supply / Q000503:physiopathology / Q000648:ultrastructure*