Effects of Intermittent Hypoxia Training With Iron Supplementation on Red Blood Cells and Iron Levels in Trained Athletes

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.

Inclusion Criteria: * Male sex * Adult age (≥18 years) * Federated mountain sports practitioner (alpinist, trail runner, ski mountaineer, or endurance runner) * Normal hemoglobin levels at screening (≥13 g/dL) * Residence at elevations below 700 m * Provision of written informed consent prior to enrollment * Agreement to comply with the principles of the Declaration of Helsinki (WMA, 2024 revision) Exclusion Criteria: * Stay at altitudes above 2,000 m within the previous 2 months prior to enrollment * Any form of anemia at screening (hemoglobin \