| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Received February 2, 2006
Revised February 27, 2006
Accepted after revision March 21, 2006
1 Copenhagen Muscle Research Centre
2 Aviation Medicine & Copenhagen Muscle Research Centre
3 Universidad de Las Palmas de Gran Canaria
* To whom correspondence should be addressed. E-mail: carsten{at}cmrc.dk.
The tight relation between arterial oxygen content and VO2max within a given person at sea level is diminished with altitude acclimatization. An explanation often suggested for this mismatch, is impairment of the muscle O2 extraction capacity with chronic hypoxia, and is the focus of the present study. We have studied six lowlanders during maximal exercise at sea level (SL) and with acute (AH) exposure to 4100 m altitude, and again after two (W2) and eight weeks (W8) of altitude sojourn, where also eight high altitude native (Nat) Aymaras were studied. Fractional arterial muscle O2 extraction at maximal exercise was 90.0 ± 1.0 % in the Danish lowlanders at sea level, and remained close to this value in all situations. In contrast to this, fractional arterial O2 extraction was 83.2 ± 2.8 in the high altitude natives, and did not change with the induction of normoxia. The capillary oxygen conductance of the lower extremity, a measure of oxygen diffusing capacity, was decreased in the Danish lowlanders after 8 weeks of acclimatization, but was still higher than the value obtained from the high altitude natives. The values were 55.2 ± 3.7 (SL), 48.0 ± 1.7 (W2), 37.8 ± 0.4 (W8), and 27.7 ± 1.5 (Nat) ml.min-1.mmHg-1. However, when correcting oxygen conductance for the observed reduction in maximal leg blood flow with acclimatisation the effect diminished. When calculating a hypothetical leg VO2max at altitude using either the leg blood flow or the O2 conductance values obtained at sea level, the former values were almost completely restored to sea level values. This would suggest that the major determinant for VO2max not to increase with acclimatization is the observed reduction in maximal leg blood flow and O2conductance.
This article has been cited by other articles:
|
|
 |
|
  C. Lundby, R. Boushel, P. Robach, K. Moller, B. Saltin, and J. A. L. Calbet During hypoxic exercise some vasoconstriction is needed to match O2 delivery with O2 demand at the microcirculatory level J. Physiol., January 1, 2008; 586(1): 123 - 130. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. van Hall COUNTERPOINT: THE LACTATE PARADOX DOES NOT OCCUR DURING EXERCISE AT HIGH ALTITUDE J Appl Physiol, June 1, 2007; 102(6): 2399 - 2401. [Full Text] [PDF]
|
|
|
|
|
|
R. S. Mazzeo, N. H. Secher, P. Rasmussen, B. Kayser, P. D. Wagner, M. Samaja, M. Guazzi, B. Grassi, M. Marzorati, B. Kayser, et al. Comments on Point:Counterpoint: "The lactate paradox does/does not occur during exercise at high altitude" J Appl Physiol, June 1, 2007; 102(6): 2403 - 2405. [Full Text] [PDF]
|
|
|
|
|
|
G. van Hall Last Word on Point:Counterpoint: The lactate paradox does/does not occur during exercise at high altitude J Appl Physiol, June 1, 2007; 102(6): 2410 - 2410. [Full Text] [PDF]
|
|
|
|
|
|
M. Amann, L. M. Romer, A. W. Subudhi, D. F. Pegelow, and J. A. Dempsey Severity of arterial hypoxaemia affects the relative contributions of peripheral muscle fatigue to exercise performance in healthy humans J. Physiol., May 15, 2007; 581(1): 389 - 403. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Guerra, A. Santana, T. Fuentes, S. Delgado-Guerra, A. Cabrera-Socorro, C. Dorado, and J. A. L. Calbet Leptin receptors in human skeletal muscle J Appl Physiol, May 1, 2007; 102(5): 1786 - 1792. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. M. Jonk, I. P. van den Berg, I. M. Olfert, D. W. Wray, T. Arai, S. R. Hopkins, and P. D. Wagner Effect of acetazolamide on pulmonary and muscle gas exchange during normoxic and hypoxic exercise J. Physiol., March 15, 2007; 579(3): 909 - 921. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
