Nine Australian male cross country ski team members (19.8±2.5 years,
(X±SD),76.6±6.4kg, 184.8±4.9cm) completed both an incremental maximal exercise
test and a 45 minute time trial performance test using a dryland ski striding technique
with poles on a treadmill. Testing occurred at 610m in a chamber that was supplied
with either an 02 enriched (p02 = 152mmHg) or an N2 enriched (p02 = 132mmHg) gas
mixture to simulate sea level (SL) or 1800m (A) conditions respectively. A 48 hour rest
interval was provided between tests and the testing conditions were randomised,
counterbalanced and double blind. At maximum effort there were significant
differences in V02 max (70.2±4.0 v 61.7±2.9 ml.kg-1.min-1), PaO2 (97.2±12.7 v
77.1±11.2 mmHg) and SaO2 (90.6±4.9 v 77.8±3.9%); but not in HR (194.1±8.1 v
191.7±7.4 bpm), VE (133.1±12.8 v 132.6±11.3 L.min-1 STPD) or [La] (14.2±2.3 v
13.7±3.3 mM) at SL v A. There was a decrease of 7.6% in overall time trial
performance between the conditions (4005±378 v 3702±301 m, p = 0.08), although
performance was significantly lower at A during the latter period of the test, >25
minutes. During the steady state stage of the time trial performance test, (=75% SL
VO2 max) there were no significant differences between SL and A in any of VO2
(52.9±5.9 v 52.1±4.9 ml.kg-'.min-' at 15 minutes for SL and A respectively); HR
(173.1±12.8 v 176.1+10.1 bpm); or [La] (3.0±1.0 v 4.8±2.2 mM). However, there
was a significant reduction in PaO2 between SL (111.2±25.5 mmHg at 15 minutes) and
A (72.6±24.3 mmHg at 15 minutes), resulting in a significant reduction in SaO2
(96.6±1.1 v 84.6±6.8% at 15 minutes) between the conditions. At the end of each lap
of the variable workload stage of the time trial performance test there were significant
reductions in VO2 (65.3±6.9, 64.2±6.3 and 66.4±5.9 v 54.6±5.6, 56.0±4.6 and
57.9±3.2 ml.kg-'.min-1 at 25, 35 and 45 minutes at SL v A); and HR (190.1 ±9.2,
192.4±8.6 and 195.9±7.6 v 181.8±12.4, 186±8.1 and 189.6±9.2 bpm) under A
conditions. There were no significant differences in [La] at the end of each lap of the
time trial performance test between SL and A, although [La] did increase over time
during the test at both SL and A (6.2±2.0, 8.9±2.8 and 10.6±4.1 v 7.6±2.0, 8.4±2.2
and 9.9± 1.8 mM). At the end of each lap of the time trial performance test, there was a
significant reduction in PaO2 (120.9±24.4, 108.8±25.9 and 103.0±23.0 v 86.0±31.4,
94.9±22.3 and 71.1±3.2 mmHg); and SaO2 (94.6±2.4, 94.3±2.4 and 92.3±3.4 v
85.9±5.8, 84.3±6.4 and 81.7±6.1%) and both PaO, and SaO2 decreased over time
during the test at both SL and A. This study has indicated that as well as the extent of
hypoxia induced by altitude, both exercise intensity and duration may impact on the
magnitude of the response to sustained exercise at altitude, such as in cross country ski
racing.
| Identifer | oai:union.ndltd.org:ADTP/218871 |
| Date | January 1999 |
| Creators | Daley, Phillipa J., n/a |
| Publisher | University of Canberra. Sports Studies |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | ), Copyright Phillipa J. Daley |
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