The Effect of Normobaric Hypoxia in Middle- and/or Long-Distance Runners: Systematic Review

Abstract

Background: The use of normobaric hypoxia can bring benefits to sports performance because it improves haematological parameters and/or physical activity tests. Our objective was to conduct a systematic review so as to analyse the methods used in hypoxia and to detect its effects on middle- and/or long-distance runners. Methods: Research was conducted using five electronic databases (PubMed, SportDiscus, Cochrane Library, Scopus and PEDro) until December 2021. The methodological quality of the included studies was assessed using the PEDro scale. Results: Having analysed 158 studies, 12 were chosen for the qualitative and quantitative synthesis. A significant improvement on time until exhaustion was detected, and oxygen saturation decreased after the intervention. There were no significant changes in the 3000-metre time trial or in the haematocrit percentage. The changes in percentage of reticulocytes, heart rate, maximal heart rate, lactate concentration and erythropoietin were heterogeneous between the different research studies. Conclusion: short exposure (less than 3 h to normobaric hypoxia significantly increases the time to exhaustion). However, longer exposure times are necessary to increase haemoglobin. Altitude and exposure time are highly heterogeneous in the included studies.

Exploiting moderate hypoxia to benefit patients with brain disease: Molecular mechanisms and translational research in progress

“…In this context, multiple variables, such as the duration, the total number of exposures, the kind of training, and the cessation of exposure, descending from high altitude versus simply stepping out of a chamber, have to be taken into account. [48][49][50][51][52][53][54] From all this work, we learn that the effects and consequences of these variable exposures are obviously diverse, including measured target functions (cognition, motor performance, others), evaluated gene expression levels, for example, from blood cells, or assessed physiological parameters. The data obtained from rodent models or even other species is certainly highly informative, but not always completely translatable to humans, apart from the fact that truly systematic investigations are rare.…”

“…Whereas exposure to high altitude results in hypobaric hypoxia, the so‐called hypoxia chambers allow the application of normobaric hypoxia, and various approaches were taken by researchers, among others in the armed forces, to even apply hyperbaric hyperoxia. In this context, multiple variables, such as the duration, the total number of exposures, the kind of training, and the cessation of exposure, descending from high altitude versus simply stepping out of a chamber, have to be taken into account 48–54 …”

“…The data obtained from rodent models or even other species is certainly highly informative, but not always completely translatable to humans, apart from the fact that truly systematic investigations are rare. Drawbacks in published human studies include the highly inconsistent experimental conditions, the small numbers of individuals tested, and the sometimes insufficient exposure time to altered O 2 levels or too low degrees of O 2 changes, to just name a few 54–57 …”

“…Drawbacks in published human studies include the highly inconsistent experimental conditions, the small numbers of individuals tested, and the sometimes insufficient exposure time to altered O 2 levels or too low degrees of O 2 changes, to just name a few. [54][55][56][57] A whole array of different methods of modulating O 2 availability has been described to influence brain functions in health and disease. Of note, potential health benefits may not be immediate consequences of hypoxia or hyperoxia per se, but may be a result of adaptations evoked by these stimuli.…”

Acute Intermittent Hypoxia Did Not Alter Pain Sensitivity or Pain Intensity Ratings for Individuals with Chronic Low Back Pain: A Pilot Study

“…AIH has been safely used in humans for many years, including to improve performance in athletic populations 7–9 and for enhancing neuroplasticity for individuals with neurologic injury. 10 The duration of AIH varies based on the population of interest.…”