Increased arterial desaturation in trained cyclists during maximal
exercise at 580 m altitude.
Cj, Gore, Hahn Ag, Scroop Gc, Watson Db, Norton Ki, Wood Rj, Campbell
Dp, Emonson Dl.
Australian Institute of Sport, Adelaide, Centre for Sport Science
and Medicine, Australian Sports Commission, Canberra, Exercise
Physiology Unit, The University of Adelaide, Institute of Aviation
Medicine, RAAF Base Edinburgh, Adelaide, School of Physical
Education, Exercise and Sport Science, University of South Australia,
Department of Human Movement Studies, The University of Western
Australia
APStracts 3:0079A, 1996.
This study utilized an hypobaric chamber to compare the effects of
mild hypobaria (MH, 50 mmHg; 580 m altitude) on blood oxygen status
and maximal oxygen consumption (O2max) in 9 untrained (UT) and 11
trained (T) cyclists with O2max values of, respectively, 51 +/- 3 and
77 +/- 1 ml.kg-1.min-1. In both groups, arterial oxygen saturation
(SaO2) decreased significantly during maximal exercise and this
effect was enhanced with MH. Both these responses were significantly
greater in the trained cyclists, where the final SaO2 during MH was
86.5 +/- 0.9%. When the group data were combined 65% of the variance
in SaO2 could be attributed to a widened AaDO2. The arterial oxygen
pressure (PaO2) during maximal exercise at sea level in the trained
group was on the steeper portion of the hemoglobin oxygen loading
curve (T, 68.3 +/- 1.3 mm Hg; UT, 89.0 +/- 2.9 mm Hg) such that a
similar decrease in PaO2 in the 2 groups in response to MH resulted
in a significantly greater fall in both SaO2 and calculated oxygen
content (ctO2) in the trained group. In consequence O2max fell
significantly only in the trained group (mean change, _ 6.8 +/- 1.5%;
range, + 1.2?to ?_?12.3%) with 70% of this decrease being due to a
fall in ctO2. This is the lowest altitude reported to decrease O2max
suggesting that trained athletes are more susceptible to a fall in
inspired oxygen pressure.
Received 8 May 1995; accepted in final form 19 January 1996.
APS Manuscript Number A486-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 February 96