In general there are two forms of hypoxia, Acute Hypoxia and Chronic Hypoxia, and both will stimulate the body to adapt. When it comes to high altitude acclimatization to CH improvements in locomotor exercise performance are commonly observed. Diving is however in the form of AH. Hypoxia promotes vessel growth by upregulating multiple pro-angiogenic pathways that mediate key aspects of endothelial, stromal, and vascular support cell biology. Studies show that hypoxia influences additional aspects of angiogenesis, including vessel patterning, maturation, and function. Cerebral capillary density and increased O2 delivery is critical to maintaining corticospinal excitability in hypoxic conditions. Reading an interesting study about hypoxic pre-conditioning, Defining the critical hypoxic threshold that promotes vascular remodeling in the brain https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4261640/, proposes that there is a threshold where significant increase in vascular density is stimulated when subjects (mice!) are exposed to CH at an oxygen level of 12%-10%. That is a 50% increase in cerebral capillary density after a 7 day exposure to CH, results are not as significant when oxygen levels are above the threshold.
Unfortunately the study does not include regular intermittent mild hypoxia (RIMH) but further research is anticipated. Doing a little interpretation/translation of the test methods the oxygen level of 12%-10% is a simulation of an approximate 14,000 ft / 4267m altitude. This can be translated to oxygen saturation SaO2(%) for practical diving vernacular as about ~62%, see http://www.high-altitude-medicine.com/SaO2-table.html. For diving, the general SaO2 level for one to "blackout" is approximately 45%-50%.
Can anyone attest to or perhaps reference a study that may suggest intermittent breath-hold training reaching SaO2 level of ~62% will drastically improve hypoxic pre-conditioning compared to anything less?
Unfortunately the study does not include regular intermittent mild hypoxia (RIMH) but further research is anticipated. Doing a little interpretation/translation of the test methods the oxygen level of 12%-10% is a simulation of an approximate 14,000 ft / 4267m altitude. This can be translated to oxygen saturation SaO2(%) for practical diving vernacular as about ~62%, see http://www.high-altitude-medicine.com/SaO2-table.html. For diving, the general SaO2 level for one to "blackout" is approximately 45%-50%.
Can anyone attest to or perhaps reference a study that may suggest intermittent breath-hold training reaching SaO2 level of ~62% will drastically improve hypoxic pre-conditioning compared to anything less?