Effects of three weeks base training at moderate simulated altitude with or without hypoxic residence on exercise capacity and physiological adaptations in well-trained male runners

Objectives: To test the hypothesis that 'live high-base train high-interval train low' (HiHiLo) altitude training, compared to 'live low-train high' (LoHi), yields greater benefits on performance and physiological adaptations. Methods: Sixteen young male middle-distance runners (age, 17.0 +/- 1.5 y; body mass, 58.8 +/- 4.9 kg; body height, 176.3 +/- 4.3 cm; training years, 3-5 y; training distance per week, 30-60 km.wk(-1)) with a peak oxygen uptake averaging similar to 65 ml.min(-1).kg(-1) trained in a normobaric hypoxia chamber (simulated altitude of similar to 2,500 m, monitored by heart rate similar to 170 bpm; thrice weekly) for 3 weeks. During this period, the HiHiLo group (n = 8) stayed in normobaric hypoxia (at similar to 2,800 m; 10 h.day(-1)), while the LoHi group (n = 8) resided near sea level. Before and immediately after the intervention, peak oxygen uptake and exercise-induced arterial hypoxemia responses (incremental cycle test) as well as running performance and time-domain heart rate variability (5-km time trial) were assessed. Hematological variables were monitored at baseline and on days 1, 7, 14 and 21 during the intervention. Results: Peak oxygen uptake and running performance did not differ before and after the intervention in either group (all P > 0.05). Exercise-induced arterial hypoxemia responses, measured both at submaximal (240 W) and maximal loads during the incremental test, and log-transformed root mean square of successive R-R intervals during the 4-min post-run recovery period, did not change (all P > 0.05). Hematocrit, mean reticulocyte absolute count and reticulocyte percentage increased above baseline levels on day 21 of the intervention (all P < 0.001), irrespective of group. Conclusions: Well-trained runners undertaking base training at moderate simulated altitude for 3 weeks, with or without hypoxic residence, showed no performance improvement, also with unchanged time-domain heart rate variability and exercise-induced arterial hypoxemia responses.