Journal of Applied Physiology, Vol 66, Issue 5 2454-2461, Copyright © 1989 by American Physiological Society

ARTICLES

Operation Everest II: adaptations in human skeletal muscle

H. J. Green, J. R. Sutton, A. Cymerman, P. M. Young and C. S. Houston
Department of Kinesiology, University of Waterloo, Ontario.

Adaptations in skeletal muscle in response to progressive hypobaria were investigated in eight male subjects [maximal O2 uptake = 51.2 +/- 3.0 (SE) ml.kg-1.min-1] over 40 days of progressive decompression to the stimulated altitude of the summit of Mt. Everest. Samples of the vastus lateralis muscle extracted before decompression (SL-1), at 380 and 282 Torr, and on return to sea level (SL-2) indicated that maximal activities of enzymes representative of the citric acid cycle, beta-oxidation, glycogenolysis, glycolysis, glucose phosphorylation, and high-energy phosphate transfer were unchanged (P greater than 0.05) at 380 and 282 Torr over initial SL-1 values. After exposure to 282 Torr, however, representing an additional period of approximately 7 days, reductions (P less than 0.05) were noted in succinic dehydrogenase (21%), citrate synthetase (37%), and hexokinase (53%) between SL-2 and 380 Torr. No changes were found in the other enzymes. Capillarization as measured by the number of capillaries per cross-sectional area (CC/FA) was increased (P less than 0.05) in both type I (0.94 +/- 0.8 vs. 1.16 +/- 0.05) and type II (0.84 +/- 0.07 vs. 1.05 +/- 0.08) fibers between SL-1 and SL-2. This increase was mediated by a reduction in fiber area. No changes were found in fiber-type distribution (type I vs. type II). These findings do not support the hypothesis, at least in humans, that, at the level of the muscle cell, extreme hypobaric hypoxia elicits adaptations directed toward maximizing oxidative function.

This article has been cited by other articles:

				M. F. Essop Cardiac metabolic adaptations in response to chronic hypoxia J. Physiol., November 1, 2007; 584(3): 715 - 726. [Abstract] [Full Text] [PDF]

				R. W. Bavis, F. L. Powell, A. Bradford, C. C.W. Hsia, J. E. Peltonen, J. Soliz, B. Zeis, E. K. Fergusson, Z. Fu, M. Gassmann, et al. Respiratory plasticity in response to changes in oxygen supply and demand Integr. Comp. Biol., October 1, 2007; 47(4): 532 - 551. [Abstract] [Full Text] [PDF]

				B. Roels, C. Thomas, D. J. Bentley, J. Mercier, M. Hayot, and G. Millet Effects of intermittent hypoxic training on amino and fatty acid oxidative combustion in human permeabilized muscle fibers J Appl Physiol, January 1, 2007; 102(1): 79 - 86. [Abstract] [Full Text] [PDF]

				C. Lundby, M. Sander, G. van Hall, B. Saltin, and J. A. L. Calbet Maximal exercise and muscle oxygen extraction in acclimatizing lowlanders and high altitude natives J. Physiol., June 1, 2006; 573(2): 535 - 547. [Abstract] [Full Text] [PDF]

				F. A. Basset, D. R. Joanisse, F. Boivin, J. St-Onge, F. Billaut, J. Dore, R. Chouinard, G. Falgairette, D. Richard, and M. R. Boulay Effects of short-term normobaric hypoxia on haematology, muscle phenotypes and physical performance in highly trained athletes Exp Physiol, March 1, 2006; 91(2): 391 - 402. [Abstract] [Full Text] [PDF]

				A. Couillard and C. Prefaut From muscle disuse to myopathy in COPD: potential contribution of oxidative stress Eur. Respir. J., October 1, 2005; 26(4): 703 - 719. [Abstract] [Full Text] [PDF]

				D. Saey, A. Michaud, A. Couillard, C. H. Cote, M. J. Mador, P. LeBlanc, J. Jobin, and F. Maltais Contractile Fatigue, Muscle Morphometry, and Blood Lactate in Chronic Obstructive Pulmonary Disease Am. J. Respir. Crit. Care Med., May 15, 2005; 171(10): 1109 - 1115. [Abstract] [Full Text] [PDF]

				M. Doucet, R. Debigare, D.R. Joanisse, C. Cote, P. LeBlanc, J. Gregoire, J. Deslauriers, R. Vaillancourt, and F. Maltais Adaptation of the diaphragm and the vastus lateralis in mild-to-moderate COPD Eur. Respir. J., December 1, 2004; 24(6): 971 - 979. [Abstract] [Full Text] [PDF]

				C. Lundby, H. Pilegaard, J. L. Andersen, G. van Hall, M. Sander, and J. A. L. Calbet Acclimatization to 4100 m does not change capillary density or mRNA expression of potential angiogenesis regulatory factors in human skeletal muscle J. Exp. Biol., October 15, 2004; 207(22): 3865 - 3871. [Abstract] [Full Text] [PDF]

				A.G.N. Agusti, A. Noguera, J. Sauleda, E. Sala, J. Pons, and X. Busquets Systemic effects of chronic obstructive pulmonary disease Eur. Respir. J., February 1, 2003; 21(2): 347 - 360. [Abstract] [Full Text] [PDF]

				B. D. Duscha, B. H. Annex, H. J. Green, A. M. Pippen, and W. E. Kraus Deconditioning fails to explain peripheral skeletal muscle alterations in men with chronic heart failure J. Am. Coll. Cardiol., April 3, 2002; 39(7): 1170 - 1174. [Abstract] [Full Text] [PDF]

				T. F. Hornbein The high-altitude brain J. Exp. Biol., March 11, 2002; 204(18): 3129 - 3132. [Abstract] [Full Text] [PDF]

				H. Hoppeler and M. Vogt Muscle tissue adaptations to hypoxia J. Exp. Biol., March 11, 2002; 204(18): 3133 - 3139. [Abstract] [Full Text] [PDF]

				T. L. Clanton and P. F. Klawitter Physiological and Genomic Consequences of Intermittent Hypoxia: Invited Review: Adaptive responses of skeletal muscle to intermittent hypoxia: the known and the unknown J Appl Physiol, June 1, 2001; 90(6): 2476 - 2487. [Abstract] [Full Text] [PDF]

				S. L. Kennedy, W. C. Stanley, A. R. Panchal, and R. S. Mazzeo Alterations in enzymes involved in fat metabolism after acute and chronic altitude exposure J Appl Physiol, January 1, 2001; 90(1): 17 - 22. [Abstract] [Full Text] [PDF]

				R. T. Hepple, M. C. Hogan, C. Stary, D. E. Bebout, O. Mathieu-Costello, and P. D. Wagner Structural basis of muscle O2 diffusing capacity: evidence from muscle function in situ J Appl Physiol, February 1, 2000; 88(2): 560 - 566. [Abstract] [Full Text] [PDF]

				H. Green, B. Roy, S. Grant, M. Burnett, R. Tupling, C. Otto, A. Pipe, and D. McKenzie Downregulation in muscle Na+-K+-ATPase following a 21-day expedition to 6,194 m J Appl Physiol, February 1, 2000; 88(2): 634 - 640. [Abstract] [Full Text] [PDF]

				R. T. Hepple, P. J. Agey, L. Hazelwood, J. M. Szewczak, R. E. MacMillen, and O. Mathieu-Costello Increased capillarity in leg muscle of finches living at altitude J Appl Physiol, November 1, 1998; 85(5): 1871 - 1876. [Abstract] [Full Text] [PDF]

				J. P. Mattson and D. C. Poole Pulmonary emphysema decreases hamster skeletal muscle oxidative enzyme capacity J Appl Physiol, July 1, 1998; 85(1): 210 - 214. [Abstract] [Full Text] [PDF]

				G. B. McClelland and G. A. Brooks Changes in MCT 1, MCT 4, and LDH expression are tissue specific in rats after long-term hypobaric hypoxia J Appl Physiol, April 1, 2002; 92(4): 1573 - 1584. [Abstract] [Full Text] [PDF]