Living high-training low increases hypoxic ventilatory response of well-trained endurance athletes

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 (similar to2,650 m); Con slept under ambient conditions (600 m). Resting, isocapnic HVR (Delta(V) over dot E/DeltaSp(O2), where (V) over dot E is minute ventilation and Sp(O2) is blood O-2 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 P-CO2 (PETCO2) and (V) over dot E were measured during room air breathing at rest. HVR (1.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 (V) over dot 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 (V) over dot E. Thus endurance athletes sleeping in mild hypoxia may experience changes to the respiratory control system.