Editor’s note. This small uncontrolled study of IHHT and blood markers in swimmers involved ten young athletes using an OXYTERRA device. It is a before-and-after observation alongside regular training, rather than a randomized comparison. Changes in blood markers do not demonstrate improved athletic performance or overall safety. The original English title says ‘hypoxia-hypoxic’, but the actual protocol alternated hypoxia and hyperoxia (IHHT); the original title is retained in the bibliographic information. Large tables have been replaced with brief results; complete data are available in the PDF. The study regimens are not instructions for unsupervised use.
Abstract
The study aimed to assess the effects of intermittent normobaric hypoxic-hyperoxic training on athletes’ biochemical and hematological parameters.
The study involved ten male swimmers aged 16–17 years, holding first-category sports qualifications or Candidate for Master of Sport status. Observations took place during the preparatory period. All participants completed a course using a Russian-made OXYTERRA device. Each session comprised five cycles: five minutes of hypoxia at an oxygen concentration of 13%, followed by three minutes of hyperoxia at a concentration of 32%.
After the course, the authors found an increase in hemoglobin concentration and a statistically significant change in lactate dehydrogenase activity. They interpret these changes as signs of improved oxygen delivery and recovery. Keywords: intermittent hypoxic-hyperoxic training, athletes, hemoglobin, creatine kinase, lactate dehydrogenase.
Introduction
Intermittent hypoxic-hyperoxic training (IHHT) at normal atmospheric pressure is used in clinical practice, but its use for athletes’ recovery and its effects on changes in hematological and biochemical markers remain insufficiently studied.
The body’s tissues require a continuous supply of oxygen in accordance with changing metabolic demands. The oxygen delivery chain begins in the lungs and ends in the mitochondria. Identifying factors that regulate individual links in this chain, restore functional status, and expand athletes’ functional reserves is an important task in sports medicine.
Hypoxia activates pulmonary ventilation, increases cardiac output, lowers blood pressure, and triggers cellular biochemical reactions aimed at overcoming oxygen deficiency [1]. According to the authors’ description, hyperoxia increases oxyhemoglobin levels and tissue oxygenation, the rate of aerobic ATP synthesis in mitochondria, and the rate of calcium transport, which affects muscle contractile function [8].
The objective was to assess the effects of IHHT on athletes’ biochemical and hematological characteristics.
Materials and methods
The experiment involved ten male swimmers aged 16–17 years, holding first-category sports qualifications or Candidate for Master of Sport status, during the preparatory period. Regular training continued 10–11 times a week for 1.5–2 hours per session.
The IHHT course using the OXYTERRA device consisted of ten sessions, 2–3 times a week. The protocol comprised five cycles, each involving five minutes of hypoxia with 13% oxygen and three minutes of hyperoxia with 32% oxygen.
Venous blood was collected before the course, after the first session, and after ten sessions. The original tables label these time points groups 1, 2, and 3; these are sequential measurements in the same athletes, rather than three independent groups.
Biochemical parameters were determined in serum from vacuum tubes containing a clot activator. Serum was obtained by centrifugation at 10 000 rpm for 15 minutes. A Mindray 800 automated biochemical analyzer was used with the manufacturer’s calibrators and control materials. Measurements included lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) activity, and concentrations of total protein, urea, creatinine, cholesterol, triglycerides, iron, phosphorus, and calcium.
A complete blood count of whole venous blood was performed using a Mindray BC-6800 Plus. Assessments included red blood cell, white blood cell, and platelet counts, hemoglobin, hematocrit, red blood cell indices, reticulocyte count, and reticulocyte hemoglobin content (RHE).
Results and discussion
Before and after the course, the authors found no complete blood count parameters outside the reference ranges. There were no statistically significant changes after the first session. After ten procedures, hemoglobin concentration was 153 ± 5 g/L and differed significantly from baseline (p = 0.01). The complete set of parameters is presented in Table 1 of the original.
Most baseline biochemical parameters were within reference ranges. CPK activity was elevated before the course: 254 ± 203 U/L, range 58–750. No statistically significant differences were found after the first session. After ten sessions, serum iron levels and LDH activity changed. CPK showed a downward trend that did not reach statistical significance.
The authors link the increase in swimmers’ hemoglobin concentration to activation of hematopoiesis during alternating hypoxia and hyperoxia [4, 6, 7]. However, red blood cell and reticulocyte counts did not increase significantly.
After the course, serum iron levels decreased (p = 0.01), remaining within reference ranges according to the authors’ assessment. Reticulocyte hemoglobin content also remained normal. The authors regard this as a physiological change; this observation alone does not demonstrate the method’s overall safety or efficacy.
Urea, creatinine, CPK, and LDH were considered markers of muscle damage during regular intensive exercise. Mean urea and creatinine values before and after the course were within reference ranges, and no effect of IHHT on these parameters was identified.
Mean CPK activity exceeded the reference level throughout the observation period. The authors note that generally accepted clinical reference values for enzyme activity do not account for the effects of exercise, so elevated values may reflect an athlete’s adaptive response [2, 5]. After the course, CPK showed a downward trend. The change in LDH activity was statistically significant; the authors interpret it as a sign of improved blood supply, oxygen delivery, and recovery [3].
IHHT and blood markers in swimmers: key laboratory findings
- Hemoglobin: 145 ± 6 → 148 ± 5 → 153 ± 5 g/L; before the course/after ten procedures p = 0.01.
- LDH: 174 ± 33 → 181 ± 28 → 152 ± 31 U/L; p = 0.04.
- Serum iron: 22 ± 5 → 20 ± 5 → 16 ± 6 µmol/L; p = 0.01.
- CPK: 254 ± 203 → 319 ± 286 → 154 ± 62 U/L; p > 0.05: a trend only.
- Other parameters in the tables: p > 0.05. No significant increase in red blood cell or reticulocyte counts was found.
Complete Table 1: complete blood count
Complete Table 2: blood biochemistry
Authors’ conclusion
The authors conclude that incorporating IHHT courses into training may accelerate recovery and improve tolerance of increasing physical workloads. They propose monitoring hemoglobin, serum iron, CPK, and LDH to assess the program. In this study, conclusions about recovery are based on laboratory markers: recovery rate, athletic performance, and oxygen delivery to tissues were not measured directly.
References
Primeneniye apparata dlya polucheniya gipoksicheskikh, giperoksicheskikh i normoksicheskikh gazovykh smesey «OXYTERRA» v klinicheskoy praktike. Guidelines. St. Petersburg, 2024. 14 p.
Callegari G.A., Novaes J.S., Neto G.R., Dias I., Garrido N.D., Dani C. Creatine Kinase and Lactate Dehydrogenase Responses after Different Resistance and Aerobic Exercise Protocols. J Hum Kinet. 2017 Aug 1;58:65–72. doi: 10.1515/hukin-2017-0071. PMID: 28828078; PMCID: PMC5548155.
Chen X., Liu L., Kang S., Gnanaprakasam J.R., Wang R. The lactate dehydrogenase (LDH) isoenzyme spectrum enables optimally controlling T cell glycolysis and differentiation. Sci Adv. 2023 Mar 24;9(12).
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Salvagno M., Coppalini G., Taccone F.S., Strapazzon G., Mrakic-Sposta S., Rocco M., Khalife M., Balestra C. The Normobaric Oxygen Paradox-Hyperoxic Hypoxic Paradox: A Novel Expedient Strategy in Hematopoiesis Clinical Issues. Int J Mol Sci. 2022 Dec 21;24(1):82. doi: 10.3390/ijms24010082. PMID: 36613522; PMCID: PMC9820104.
Technology and practice
Oxygen regimens and session monitoring are explained in the section ‘IHHT technology’.
The topic of IHHT in sport and recovery is discussed in the Applications section.
Operating modes and the interface are described on the page for the OXYTERRA RS device.