The present study aimed to compare sleep disordered breathing during live high-train low (LHTL) altitude camp using normobaric hypoxia (NH) and hypobaric hypoxia (HH). Sixteen highly trained triathletes completed two 18-day LHTL camps in a crossover designed study. They trained at 1100-1200 m while they slept either in NH at a simulated altitude of 2250 m or in HH. Breathing frequency and oxygen saturation (SpO(2)) were recorded continuously during all nights and oxygen desaturation index (ODI 3%) calculated. Breathing frequency was lower for NH than HH during the camps (14.6 +/- 3.1 breath x min(-1) vs. 17.2 +/- 3.4 breath x min(-1), p < 0.001). SpO(2) was lower for HH than NH (90.8 +/- 0.3 vs. 91.9 +/- 0.2, p < 0.001) and ODI 3% was higher for HH than NH (15.1 +/- 3.5 vs. 9.9 +/- 1.6, p < 0.001). Sleep in moderate HH is more altered than in NH during a LHTL camp.