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Effects of Intermittent Hypoxia Training With Iron Supplementation on Red Blood Cells and Iron Levels in Trained Athletes (IHIT-IRON)

17. juli 2026 opdateret af: Néstor Vicente-Salar

SHORT-TERM INTERMITTENT HYPOXIA TRAINING INDUCES POSITIVE ERYTHROPOIETIC ADAPTATIONS BUT DECREASING DRASTICALLY IRON RESERVES

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.

Studieoversigt

Status

Afsluttet

Betingelser

Intervention / Behandling

Undersøgelsestype

Interventionel

Tilmelding (Faktiske)

32

Fase

  • Ikke anvendelig

Kontakter og lokationer

Dette afsnit indeholder kontaktoplysninger for dem, der udfører undersøgelsen, og oplysninger om, hvor denne undersøgelse udføres.

Studiesteder

  • Spanien
    • Alicante
      • Elche, Alicante, Spanien, 03202
        • University Miguel Hernández of Elche

Deltagelseskriterier

Forskere leder efter personer, der passer til en bestemt beskrivelse, kaldet berettigelseskriterier. Nogle eksempler på disse kriterier er en persons generelle helbredstilstand eller tidligere behandlinger.

Berettigelseskriterier

Aldre berettiget til at studere

  • Voksen

Tager imod sunde frivillige

Ja

Beskrivelse

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 <12-13 g/dL)
  • Sports-related pseudoanemia
  • Presence of cardiovascular or respiratory pathologies, as determined by the medically supervised VO₂max exercise test
  • Female sex

Studieplan

Dette afsnit indeholder detaljer om studieplanen, herunder hvordan undersøgelsen er designet, og hvad undersøgelsen måler.

Hvordan er undersøgelsen tilrettelagt?

Design detaljer

  • Primært formål: Behandling
  • Tildeling: Randomiseret
  • Interventionel model: Parallel tildeling
  • Maskning: Enkelt

Våben og indgreb

Deltagergruppe / Arm
Intervention / Behandling
Placebo komparator: Control group (CG)
Trained at sea-level conditions
Andet: Control group (CG)
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).
Eksperimentel: Hypoxia group (HG)
Trained at simulated altitudes between 4,450 and 5,850 m
Andet: Hypoxia group (HG): trained at simulated altitudes between 4,450 and 5,850 m
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).

Hvad måler undersøgelsen?

Primære resultatmål

Resultatmål
Foranstaltningsbeskrivelse
Tidsramme
Hemoglobin concentration
Tidsramme: Baseline and 3 weeks (end of intervention)
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.
Baseline and 3 weeks (end of intervention)

Sekundære resultatmål

Resultatmål
Foranstaltningsbeskrivelse
Tidsramme
Red blood cell count
Tidsramme: Baseline and 3 weeks (end of intervention)
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.
Baseline and 3 weeks (end of intervention)
Hematocrit
Tidsramme: Baseline and 3 weeks (end of intervention)
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.
Baseline and 3 weeks (end of intervention)
Serum ferritin
Tidsramme: Baseline and 3 weeks (end of intervention)
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.
Baseline and 3 weeks (end of intervention)
Reticulocyte count
Tidsramme: Baseline and 3 weeks (end of intervention)
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.
Baseline and 3 weeks (end of intervention)

Samarbejdspartnere og efterforskere

Det er her, du vil finde personer og organisationer, der er involveret i denne undersøgelse.

Sponsor

Néstor Vicente-Salar

Efterforskere

  • Studieleder: Enrique Roche, Full Professor, University Miguel Hernández of Elche

Datoer for undersøgelser

Disse datoer sporer fremskridtene for indsendelser af undersøgelsesrekord og resumeresultater til ClinicalTrials.gov. Studieregistreringer og rapporterede resultater gennemgås af National Library of Medicine (NLM) for at sikre, at de opfylder specifikke kvalitetskontrolstandarder, før de offentliggøres på den offentlige hjemmeside.

Studer store datoer

Studiestart (Faktiske)

23. oktober 2011

Primær færdiggørelse (Faktiske)

30. juni 2014

Studieafslutning (Faktiske)

15. juli 2014

Datoer for studieregistrering

Først indsendt

17. juli 2026

Først indsendt, der opfyldte QC-kriterier

17. juli 2026

Først opslået (Faktiske)

22. juli 2026

Opdateringer af undersøgelsesjournaler

Sidste opdatering sendt (Faktiske)

22. juli 2026

Sidste opdatering indsendt, der opfyldte kvalitetskontrolkriterier

17. juli 2026

Sidst verificeret

1. december 2014

Mere information

Begreber relateret til denne undersøgelse

Yderligere relevante MeSH-vilkår

Andre undersøgelses-id-numre

  • PS09/01093

Plan for individuelle deltagerdata (IPD)

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