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1 School of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Lidcombe, New South Wales 2141; 2 Department of Physiology, Australian Institute of Sport, Canberra, Australian Capital Territory 2616; 3 Exercise Metabolism Group, School of Medical Science, Royal Melbourne Institute of Technology University, Bundoora, Victoria 3083; and 4 School of Human Movement, Recreation, and Performance, Centre for Rehabilitation, Exercise, and Sports Sciences, Victoria University of Technology, Melbourne, Victoria 8001, Australia
This study determined whether
"living high-training low" (LHTL)-simulated altitude exposure
increased the hypoxic ventilatory response (HVR) in well-trained
endurance athletes. Thirty-three cyclists/triathletes were divided into
three groups: 20 consecutive nights of hypoxic exposure (LHTLc,
n = 12), 20 nights of intermittent hypoxic exposure
(four 5-night blocks of hypoxia, each interspersed with 2 nights of
normoxia, LHTLi, n = 10), or control (Con,
n = 11). LHTLc and LHTLi slept 8-10 h/day
overnight in normobaric hypoxia (~2,650 m); Con slept under ambient
conditions (600 m). Resting, isocapnic HVR
(
E/SpO2, where
E is minute ventilation and
SpO2 is blood O2 saturation) was
measured in normoxia before hypoxia (Pre), after 1, 3, 10, and 15 nights of exposure (N1, N3, N10, and N15, respectively), and 2 nights
after the exposure night 20 (Post). Before each HVR test,
end-tidal PCO2
(PETCO2) and E were
measured during room air breathing at rest. HVR
(l · min
1 · %1)
was higher (P < 0.05) in LHTLc than in Con at N1
(0.56 ± 0.32 vs. 0.28 ± 0.16), N3 (0.69 ± 0.30 vs.
0.36 ± 0.24), N10 (0.79 ± 0.36 vs. 0.34 ± 0.14), N15
(1.00 ± 0.38 vs. 0.36 ± 0.23), and Post (0.79 ± 0.37 vs. 0.36 ± 0.26). HVR at N15 was higher (P < 0.05) in LHTLi (0.67 ± 0.33) than in Con and in LHTLc than in LHTLi. PETCO2 was depressed in LHTLc and
LHTLi compared with Con at all points after hypoxia
(P < 0.05). No significant differences were observed
for E at any point. We conclude that LHTL increases HVR in endurance athletes in a time-dependent manner and decreases PETCO2 in normoxia, without change in
E. Thus endurance athletes sleeping in mild hypoxia
may experience changes to the respiratory control system.
altitude training; chemoresponsiveness; cyclists; triathletes; ventilatory acclimatization
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