Hemoglobin mass and performance responses during 4 weeks of normobaric "live high-train low and high"

To investigate whether 4 weeks of normobaric "live high-train low and high" (LHTLH) causes different hematological, cardiorespiratory, and sea-level performance changes compared to living and training in normoxia during a preparation season.

Nineteen (13 women, 6 men) cross-country skiers competing at the national or international level completed a 28-day period (∼18 h day^-1 ) of LHTLH in normobaric hypoxia of ∼2400 m (LHTLH group) including two 1 h low-intensity training sessions per week in normobaric hypoxia of 2500 m while continuing their normal training program in normoxia. Hemoglobin mass (Hb_mass ) was assessed using a carbon monoxide rebreathing method. Time to exhaustion (TTE) and maximal oxygen uptake (VO_2max ) were measured using an incremental treadmill test. Measurements were completed at baseline and within 3 days after LHTLH. The control group skiers (CON) (seven women, eight men) performed the same tests while living and training in normoxia with ∼4 weeks between the tests.

Hb_mass in LHTLH increased 4.2 ± 1.7% from 772 ± 213 g (11.7 ± 1.4 g kg^-1 ) to 805 ± 226 g (12.5 ± 1.6 g kg^-1 ) (p < 0.001) while it was unchanged in CON (p = 0.21). TTE improved during the study regardless of the group (3.3 ± 3.4% in LHTLH; 4.3 ± 4.8% in CON, p < 0.001). VO_2max did not increase in LHTLH (61.2 ± 8.7 mL kg^-1  min^-1 vs. 62.1 ± 7.6 mL kg^-1  min^-1 , p = 0.36) while a significant increase was detected in CON (61.3 ± 8.0-64.0 ± 8.1 mL kg^-1  min^-1 , p < 0.001).

Four-week normobaric LHTLH was beneficial for increasing Hb_mass but did not support the short-term development of maximal endurance performance and VO_2max when compared to the athletes who lived and trained in normoxia.