Background Altitude training produces advantages over sea level training, but athletes require acclimatization to avoid discomfort or mountain sickness, in which the blood pressure control is essential.

Objective To investigate the influence of moderate altitude on blood pressure and renin-angiotensin-aldosterone systems in a women's volleyball team (Honor Division – Spain).

Design We assessed 14 elite female volleyball players: 2 weeks under normoxia conditions (640 m above sea level), 2 weeks under relative hypoxia (2450 m, at the High Performance Centre of Sierra Nevada, Granada, Spain) and two final weeks back to normoxia.

Setting and 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 of the participants reported ingesting contraceptives or hormonal treatments.

Interventions The volleyball players trained twice/day (3 h/session). The blood pressure was measured at rest in the morning, during and after physical exercise (both in the morning and in the afternoon season), as well as in urine/24 h the renin, angiotensin and aldosterone, renal water excretion and urinary volume every 5 days.

Independent variable: Altitude.

Dependent variables: Renin, angiotensin, aldosterone 24/h urinary levels; rest, pre and posttraining blood pressure.

Results The aldosterone levels decreased in the first hypoxic week (157.09 pg/ml; p<0.05 respect to level), as well as renin levels (12.82 pg/ml p<0.05 respect to level). There was an increase in renal water excretion (25 701.36 ml/day with a p<0.05). The diastolic blood pressure posttraining showed changes between the hypoxia and normoxia (69.72±12.3 vs 73.45±14.9 mm Hg p<0.05).

Conclusions Renin is reduced under hypoxia. Post-exercise diastolic blood pressure changes significantly at altitude with less venous return and may explain symptoms of mountain sickness.