Combined intermittent hypoxic exposure at rest and continuous hypoxic training can maintain elevated hemoglobin mass after a hypoxic camp.

Athletes use hypoxic living and training to increase hemoglobin mass (Hb mass ), but Hb mass declines rapidly upon return to sea level. We investigated whether intermittent hypoxic exposure (IHE) + continuous hypoxic training (CHT) after return to sea level maintained elevated Hb mass , and if changes in Hb mass were transferred to changes in maximal oxygen uptake (V̇o 2max ) and exercise performance. Hb mass was measured in 58 endurance athletes before (PRE), after (POST1), and 30 days after (POST2) a 27 ± 4-day training camp in hypoxia ( n = 44, HYP) or at sea level ( n = 14, SL). After returning to sea level, 22 athletes included IHE (2 h rest) + CHT (1 h training) in their training every third day for 1 mo (HYP IHE + CHT ), whereas the other 22 HYP athletes were not exposed to IHE or CHT (HYP SL ). Hb mass increased from PRE to POST1 in both HYP IHE + CHT (4.4 ± 0.7%, means ± SE) and HYP SL (4.1 ± 0.6%) (both P < 0.001). Compared with PRE, Hb mass at POST2 remained 4.2 ± 0.8% higher in HYP IHE + CHT ( P < 0.001) and 1.9 ± 0.5% higher in HYP SL ( P = 0.023), indicating a significant difference between the groups ( P = 0.002). In SL, no significant changes were observed in Hb mass with mean alterations between -0.5% and 0.4%. V̇o 2max and time to exhaustion during an incremental treadmill test ( n = 35) were elevated from PRE to POST2 only in HYP IHE + CHT (5.8 ± 1.2% and 5.4 ± 1.4%, respectively, both P < 0.001). IHE + CHT possesses the potential to mitigate the typical decline in Hb mass commonly observed during the initial weeks after return to sea level. NEW & NOTEWORTHY Sets of 2-h intermittent hypoxic exposure + 1-h continuous hypoxic training, every third day, possess the potential to mitigate the typical decline in Hb mass that is commonly observed during the initial weeks after return to sea level from an altitude camp. Inclusion of IHE + CHT in the training regimen was also accompanied by improvements in V̇o 2max and exercise performance in most but not all Tier 3-Tier 5 level endurance athletes during the training season.