Muscle structure and performance capacity of Himalayan Sherpas.
The ultrastructure of the vastus lateralis muscle of Sherpas from Nepal [5 males; age 28 +/- 2.8 (SD) yr, indirect maximal O2 consumption 48.5 +/- 5.4 ml.kg(-1).min(-1)] was assessed and compared with those of sedentary lowlanders and of Caucasian climbers before and after high-altitude exposure. The mean cross-sectional area of the fibers was 3,186 +/- 521 microns2, i.e., similar to those of Caucasian elite high-altitude climbers (3,108 +/- 303 microns2) and a group of climbers after a 6- to 8-wk sojourn at 5,000-8,600 m (3,360 +/- 580 microns2) but significantly (P less than 0.05) smaller than that of unacclimatized climbers (4,170 +/- 710 microns2) and slightly, although not significantly, lower than that of sedentary lowlanders (3,640 +/- 260 microns2). The number of capillaries per square millimeter of muscle cross section was 467 +/- 22, not significantly smaller than those of climbers on return from a Himalayan expedition (538 +/- 89) and elite high-altitude climbers (542 +/- 127) but significantly (P less than 0.05) greater than that of sedentary lowlanders (387 +/- 25). The volume density of mitochondria was 3.96 +/- 0.54%, significantly (P less than 0.05) less than the values found for any other investigated group, including sedentary subjects at sea level (4.74 +/- 0.30%). It is concluded that Sherpas, like acclimatized Caucasian climbers, are characterized by 1) facilitated convective and diffusive muscle O2 flow conditions and 2) a higher maximal O2 consumption-to-mitochondrial volume ratio than lowlanders despite a reduced mitochondrial volume density.
Kayser
B
B
Department of Physiology, Centre Médical Universitaire, Geneva, Switzerland.
Hoppeler
H
H
Claassen
H
H
Cerretelli
P
P
D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D000531:Altitude; D002196:Capillaries / Q000648:ultrastructure; D006801:Humans; D000860:Hypoxia / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008931:Mitochondria, Muscle / Q000648:ultrastructure; D009051:Mountaineering; D009119:Muscle Contraction; D009132:Muscles / Q000098:blood supply / Q000502:physiology / Q000648:ultrastructure*; D009390:Nepal; D010807:Physical Endurance