An interventional study of Control group (CG) and Hypoxia group (HG): trained at simulated altitudes between 4,450 and 5,850 m in Hypoxia, Erythropoiesis and Iron Metabolism Disorders, sponsored by Néstor Vicente-Salar. Completed at 1 site in Spain. Open to male participants aged 18 Years to 60 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-22.
Sponsored by Néstor Vicente-Salar · Not applicable, Interventional, and Treatment
This study investigates how training under conditions of reduced oxygen (intermittent hypoxia) affects the body's ability to produce red blood cells and manage iron levels, compared to training under normal oxygen conditions. Red blood cells are essential for transporting oxygen throughout the body, and their production depends on having enough available iron.
Thirty-two physically trained participants completed a 3-week training program, either in low-oxygen conditions or in normal oxygen conditions. All participants followed the same diet and received daily supplements of iron and vitamins to ensure adequate nutritional support.
The main hypothesis of this study is that training in low-oxygen conditions stimulates the production of red blood cells more strongly than training in normal oxygen conditions, and that this increased production requires the body to use stored iron, potentially lowering iron reserves.
Results showed that participants training in low-oxygen conditions experienced a greater increase in red blood cells and related markers compared to those training in normal conditions. At the same time, their stored iron levels decreased, suggesting that the body was using its iron reserves to support the increased production of red blood cells. In contrast, participants training in normal oxygen conditions showed smaller changes and maintained or slightly increased their iron stores.
These findings suggest that low-oxygen training can enhance the body's capacity to produce red blood cells but may also reduce iron reserves. This highlights the importance of monitoring iron levels during such training programs, especially in athletes or individuals with conditions related to low oxygen availability, such as anemia.
Overall, this study aims to improve understanding of how oxygen availability influences blood health and may help guide future strategies that combine hypoxia training and iron supplementation to support performance and treat certain medical conditions.
1,231 studies on the registry are indexed under Hypoxia; 241 are open to participants now.
This study's enrollment of 32 is below the median of 45 across 853 interventional studies indexed under Hypoxia.
Browse Hypoxia studies →This is the only study on the registry with Néstor Vicente-Salar as lead sponsor.
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Exclusion Criteria:
Trained at sea-level conditions
Other: Control group (CG)
Trained at simulated altitudes between 4,450 and 5,850 m
Other: Hypoxia group (HG): trained at simulated altitudes between 4,450 and 5,850 m
3-week normoxic training program (14 sessions, 90 min/session) with identical exercise structure to the hypoxia group (strength-resistance circuit + cycling intervals), performed at sea-level oxygen conditions inside the same tent to ensure blinding. Frequency: 4-5 sessions/week. All participants received daily oral supplementation: iron 60 mg (ferrous sulfate + ferrous fumarate) + vitamin C 200 mg + folic acid 200 µg + vitamin B12 6 µg. Diet provided \~55 kcal/kg/day (carbohydrates 7-8 g/kg, protein 1.6-2 g/kg, fat 1-1.5 g/kg).
3-week normobaric intermittent hypoxia training program (14 sessions, 90 min/session: 60 min active + 30 min passive hypoxia) at simulated altitudes of 4,450-5,850 m (SaO₂ \~80%). Training combined strength-resistance circuit (30 min) and high-intensity cycling intervals (30 min). Frequency: 4-5 sessions/week. All participants received daily oral supplementation: iron 60 mg (ferrous sulfate + ferrous fumarate) + vitamin C 200 mg + folic acid 200 µg + vitamin B12 6 µg. Diet provided \~55 kcal/kg/day (carbohydrates 7-8 g/kg, protein 1.6-2 g/kg, fat 1-1.5 g/kg).
Hemoglobin concentration
Venous blood hemoglobin concentration (g/dL) measured at baseline and 3 days after completion of the 3-week intervention. Blood samples collected in the morning (08:00-10:00 h) after overnight fast (≥8 h) and 10 min of seated rest, analyzed by automated laboratory analyzer following CLSI standards.
Time frame: Baseline and 3 weeks (end of intervention)
Red blood cell count
Venous blood erythrocyte concentration (×10⁶ cells/mm³) measured at baseline and 3 days after completion of the 3-week intervention. Blood samples collected in the morning (08:00-10:00 h) after overnight fast (≥8 h) and 10 min of seated rest, analyzed by automated laboratory analyzer following CLSI standards.
Time frame: Baseline and 3 weeks (end of intervention)
Hematocrit
Percentage of red blood cells in total blood volume (%) measured at baseline and 3 days after completion of the 3-week intervention. Blood samples collected under identical conditions to primary outcome measure.
Time frame: Baseline and 3 weeks (end of intervention)
Serum ferritin
Serum ferritin concentration (ng/mL) as an indicator of iron storage status, measured at baseline and 3 days after completion of the 3-week intervention. Obtained from serum separator tubes analyzed by automated laboratory analyzer following CLSI standards.
Time frame: Baseline and 3 weeks (end of intervention)
Reticulocyte count
Percentage of reticulocytes (immature red blood cells) in peripheral blood (%), used as an indirect indicator of erythropoietic activity. Measured at baseline and 3 days after completion of the 3-week intervention under identical sampling conditions.
Time frame: Baseline and 3 weeks (end of intervention)
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