Background Athletes from many endurance disciplines include altitude training in their yearly training programme. In volleyball, it is necessary to clarify the haematological benefits and improvement in sports performance.

Objective To investigate the influence of moderate altitude on haematological variables in a women's volleyball team (Honor Division – Spain).

Design and setting We assessed 14 elite female volleyball players for two weeks in normoxia (640 m above sea level), two weeks in relative hypoxia (2450 m, at the High Performance Center of Sierra Nevada, Granada, Spain) and two final weeks in normoxia again, during the volleyball preseason (August–September).

Participants 14 women (mean age 23±2.8 years; height: 184.9±6.9 cm; weight: 73.1±6.2 kg). All players who started the study completed it. None were taking dietary supplements, vitamins or exogenous iron. During the study, all players menstruated.

Interventions The volleyball players trained twice daily (3 h/season). Blood samples were taken at 7-day intervals in normoxia and 72 h in hypoxia. Economy of effort was evaluated by the relationship between oxygen intake (Vo₂) and running speed on a treadmill using sport-specific protocols. Blood samples were taken monthly during volleyball season.

Independent Variable: Altitude.

Dependent Variables: Haematological and VO₂ intake.

Results Higher levels of haemoglobin (14.1±1.2 g/dl) and hematocrit (42.7±2.2%) were obtained at normoxia prealtitude, while the lowest levels were obtained in the first week post-altitude (12.9±1.8 g/dl; 38.9±2.3% respectively; p<0.05). After the stay at altitude, oxygen intake was increased (48.1±1.5 to 51.4±2.3 ml/kg/min; p<0.05).

Conclusions 2 weeks of moderate hypoxia improved the maximum oxygen intake but not the haemoglobin or hematocrit levels.