Intermittent hypoxic training

1. Intermittent hypoxic training

2. Intermittent hypoxic training (or therapy) (IHT) • is a non-invasive, drug-free technique aiming to improve human performance and well-being using the phenomena of adaptation to reduced oxygen. • Consists of exposure to alternating periods of hypoxia (9 - 14% O2 inhaled through a mask) and reoxygenation with atmospheric air

3. An IHT session constitutes a few minutes interval of breathing low oxygen (hypoxic) air alternated with an ambient or hyperoxic air over a 45- to 90-minute session per day. • A full treatment course is 3–4 weeks

4. IHT can be beneficial • chronic heart and lung diseases • hypertension • asthma and chronic bronchitis • liver and pancreatic diseases • anxiety and depression • iron-deficiency anaemia • lack of energy and fatigue • mitochondrial status • aerobic and anaerobic performance

5. IHT is contra-indicated in case of • acute somatic and viral diseases • chronic obstructive pulmonary disease (COPD-II and COPD-III) • chronic diseases with symptoms of decompensation or terminal illness • individual intolerance of oxygen insufficiency • cancer, unless IHT is prescribed by a doctor • people with epilepsy, pacemakers or heart arrhythmias, unless treatment (including IHT) is under direct medical supervision

6. Hypoxic Training index (HTi) • provides an objective measure of the hypoxic stress delivered during the Intermittent Hypoxic Training (IHT) session, • compared to simple recording the inhaled fraction of oxygen (FiO2). HTi provides a figure (index) of dosage received by the individual at the end of the session.

7. Knowledge of HTi can therefore be used to alter the training regime for different individuals, compensating for individual variability, and can be used in scientific studies to ensure that subject exposure was correctly controlled • Tissue hypoxia develops only when arterial oxygen saturation (SpO2) drops to 90% or below. This is due to the oxyhaemoglobin dissociation curve. Saturations above 90% produce very little effect or decrease of arterial oxygen partial pressure (PaO2)

8. In order to obtain consistent and comparable values of HTi for different individuals the following conditions should be stipulated: • The values of SpO2 above 89% are not considered in the calculation of HTi, as such saturation levels do not contribute to the treatment. SpO2 values below 75% count as 75%. • HTi is calculated as an integral value of SpO2 readings made with 1 s sampling frequency and divided by 60 in order to produce a “per minute” value. • During the treatment target SpO2 values are in the range of 75% - 89%.

9. where:HTi : Hypoxic Training index,t : period of time, andSpO2 (t) : SpO2 (%), arterial oxygen saturation value measured at one-second intervals

10. How the HTi is calculated: Only part of the IHT session is shown, the targeted SpO2 value is 80% as an example. The filled part of the SpO2 graph represents the amount of hypoxia delivered, “dosage”. • This image shows a typical SpO2 curve during a full biofeedback-controlled IHT session. (FiO2 is altered automatically using biofeedback controlled hypoxicator to attain and sustain the desired SpO2 target value

11. IHT Effects on the brain • dopamine and seratonin, associated with positive mood and calmness, showed quite a significant increase in people who underwent a three-week course of intermittent hypoxic acclimatisation. • Norepinephrine, sympathetic nervous system and the so-called 'fight ' response, was decreased.

12. A study showed that after twice daily sessions of IHT lasting 60 to 90 min, athletes‘ performance improved by 2.9%

13. Physiological Responses to IHT • Increase capillary density • Shift SpO2 curve to the right • Increase EPO

14. Common Myeloid Progenitor Development of Red Blood Cells Feedback control loop • First red cells are produced in the yolk sac. Later red cell production shifts to the liver, spleen and then the bone marrow. • Feedback control of RBC Production is through Erythropoietin (Epo). • Necessary to prevent death and promote proliferation of committed precursors • Shifts non-committed progenitor cells into the erythroid lineage • Produced in renal tubular epithelial cells and more widely in the growing embryo • Feedback control targets the first committed cell in the erythroid lineage.

15. EPO gene • In humans and other mammals, hypoxia modulates EPO levels by increasing expression of the EPO gene • mechanism is the transcription factor complex hypoxia-inducible factor (HIF)-1 • It plays an essential role in cellular and systemic responses to hypoxia • This is one of the class of hypoxia inducible factors, a family that includes Hif1a, Hif2a, and Hif3a

16. What regulates Erythropoietin (Epo) Production? Semenza G.L.Cell. 2001 Oct 5;107(1):1-3 • Epo is regulated transcriptionally by an regulatory region near the gene • This regulatory region binds HIF (Hypoxia Induced Factor) • Hypoxia regulates HIF • HIF also activates VEGF and induces vasculogenesis- a problem in pregnancy

17. HIF-1 • Hypoxia-inducible factor 1, alpha subunit (basic helix-loop-helix transcription factor) • Gene Code: Chr.14:q23.2 • Induces EPO synthesis • Blocked by HIF prolyl-hydroxylase

18. In hypoxic conditions, HIF prolyl-hydroxylase is inhibited, since it utilizes oxygen as a co-substrate • Hypoxia also results in a buildup of succinate, due to inhibition of the electron transport chain in the mitochondria • The buildup of succinate further inhibits HIF prolyl-hydroxylase action, since it is an end-product of HIF hydoxylation • By inhibiting HIF prolyl-hydroxylase, the activity of HIF-1α in the bloodstream is prolonged, which results in an increase in endogenous production of erythropoetin

19. Hypoxia Prevents Degradation of HIF-1 If HIF-1 Controls Epo, what Controls HIF-1? PHD = proline hydroxylase

20. Capillary network formation under Hypoxia • Capillary network formation. Cells seeded formed capillary-like structure at approximately 4–5 h, which was more prominent in hypoxia (b) as compared to normoxia (a). When HIF-2 clone was cultured in hypoxia (c), network formation was even more evident than hypoxic, control endothelial cells. A magnified view (d) shows representative vascular sprouting (arrows), which was larger in number in order of (c)>(b)>(a). The capillary network formation was enumerated after 24 h of hypoxic incubation by measuring the length of capillary structures (e). • Hypoxia alone promoted network formation, which became even more evident by overexpressing HIF-2

22. Vascular endothelial growth factor (VEGF) • is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. It is part of the system that restores the oxygen supply to tissues when blood circulation is inadequate. • VEGF's normal function is to create new blood vessels during embryonic development, new blood vessels after injury, muscle following exercise, and new vessels (collateral circulation) to bypass blocked vessels

23. Hypoxia induced VEGF • When a cell is deficient in oxygen, it produces hypoxia-inducible factor, a transcription factor. HIF stimulates the release of VEGF, among other functions (including modulation of erythropoeisis). • Circulating VEGF then binds to VEGF Receptors on endothelial cells, triggering a Tyrosine Kinase Pathway leading to angiogenesis.

24. SpO2 Curve • oxygen saturation refers to oxygenation, or when oxygen molecules (O2) enter the tissues of the body. • In this case blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood. • As a result of this oxygenation, the color of the blood changes from dark purple to red. • Oxygen saturation, or O2sats measure the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen

26. Discussion • Which athletic sport may be the most suitable implementing iHTs and why? • What is intermittent hypoxic training and it’s strengths, weakness, opportunity, threat on athlete in practicing. • Why iHTs is so important onto HIF and VEGF. How these substances can beneficial on functional capacity of body.