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Background: Once used by mountaineers to facilitate rapid adaptations to altitude and by athletes to improve their aerobic capacity, exposure to hypoxia has been proven to affect various physiological, clinically relevant parameters. A form of conditioning known as Intermittent Hypoxia Conditioning (IHC) consists of repeated exposures to intermittent hypoxia, combined with normoxia and hyperoxia, which has been shown to have potential as a treatment to improve cardio-metabolic risks profile in cardiac patients but results across studies are inconsistent. This systematic review and meta-analysis aims to evaluate the clinical effectiveness of IHC. Methods: Four electronic databases (PubMed, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials) were searched (from inception to December 2019) to retrieve all studies focused on IHC in elderly patients with cardiovascular disease. A meta-analysis of functional, efficacy, and safety outcomes in cardiac patients was completed to compare IHC to sham treatments. Results: Fourteen studies with 320 patients in the interval hypoxia-normoxia group (IHNG) or interval hypoxia–hyperoxia training group (IHHG) and 111 patients in the control group were included in our meta-analysis. IHNT and IHHT were associated with significant reduction in heart rate, SBP, and DBP at rest after treatment [MD= −5.35 beat/min, 95% CI (−9.19 to -1.50), p=0.006], [MD= −13.72 mmHg, 95% CI (−18.31 to −9.132), p<0.001], and [MD= −7.882 mmHg, 95% CI (−13.163 to −2.601), p=0.003], respectively. There were no significant complications or serious adverse events related to IHNT/IHHT. Conclusion: The current evidence suggested that the use of the IHNT/IHHT program in elderly patients with CVDs can be safe and effective in terms of heart rate and elevated blood pressure. However, currently, there is no supporting evidence that IHNT/IHHT can significantly improve the hematological parameters, lipid profile, or exercise tolerance. Further research is needed.

Objective: The research was carried out to test the influence of adaptation to passive whole body hyperthermia (PH) on physical capacity and cardio-respiratory efficiency in men-amateur athletes under the testing load of increasing intensity in laboratory thermal-neutral conditions. Twenty-eight amateur athletes (males, mean age 20.2 ± 2.1 y.o., game-based kinds of sports-football, handball, training experience-4-7 years) were randomized into two groups: experimental (14 people), who underwent 24 PH procedures, and control (14 people), who underwent 24 light training sessions in interval regime on elliptical gym apparatus. Results: Adaptation to PH was accompanied by moderate increase of aerobic efficiency and cardio-respiratory endurance in amateur athletes under thermally neutral conditions, while interval training in the control group showed no reliable changes in efficiency. Conclusion: A 10-week course of PH procedures leads to the increase of peak oxygen consumption, oxygen consumption at the level of anaerobic threshold, and heart efficiency (enhancement of oxygen pulse values), as well as efficiency of pulmonary ventilation and bronchial conductance, which we consider to be cross effects of adaptation to passive whole-body repetitive hyperthermia.

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