Hypoxic exposure to increase exercise performance: beneficial aspects and potential drawbacks

The primary aim of this PhD project is to provide further insights intothe physiological mechanisms underlying physiological adaptation to hypoxic training (~altitude training), and to optimize hypoxic training strategies to enhance endurance exercise performance. This includes evaluation of the potential effects of nitrate supplementation on the physiological and performance effects of hypoxic training. Environmental and exercise-induced hypoxia in muscle tissue is presumed to play a role in physiological and performance effects of endurance training. Oxygen sensor PHD1 and its regulation of HIF-α are thus supposed to play an important role in the adaptations to endurance training. To test this hypothesis and further explore the role of PHD1, genetically modified micewith a knock-out in the PHD1 gene will be subjected to 6 weeks of endurance training in normoxic or hypoxic (14.0% O2) environment. Exercise performance will be tested before and after the intervention. Biochemical and histochemical analyses of muscle tissue will be performed to investigate metabolic and structural adaptations of muscle tissue. In a second study, the effects of hypoxia and nitrate supplementation on the physiological and performance effects of SIT will be evaluated. In this light, 3 experimental groups with each 10 moderately-trained male subjects will be enrolled in a 5-week sprint interval training programme on a cycle ergometer. A first group will perform their training sessions in normoxic environment (20.9% O2) and will receive a placebo supplement (Nor-Plac). A second group will train in normobaric hypoxia (15.0% O2) and will receive a placebo supplement (Hyp-Plac). A third group will train in normobaric hypoxia (15.0% O2) and will receive a nitrate supplement (6.45 mmol sodium nitrate ~400 mg) before each training session.Before and after the intervention period, needle biopsies from m. vastus lateralis will be taken for biochemical analysis. Aerobic and anaerobic exercise tests will be performed to evaluate training effects. The aim of a third study is to unravel the underlying mechanisms by whichhypoxia and nitrate supplementation interact with muscular adaptations to endurance training. Muscle tissue from 55 subjects who have been enrolled in a 6-week training programme will be analyzed by means of WesternBlot and RT-qPCR techniques. In a previously conducted study, subjects were randomly assigned to one of the 5 experimental groups: (1) trainingin normoxia consuming a placebo drink (Tr-Nor-Plac), (2) training in normoxia consuming beetroot juice (Tr-Nor-BR), (3) training in hypoxia consuming a placebo drink (Tr-Hyp-Plac), (4) training in hypoxia consuming beetroot juice (Tr-Hyp-BR) and finally (5) a sedentary group not exposedto hypoxia consuming beetroot juice (Sed-Nor-BR). The trainingprogramme consisted of 5 training sessions per week of 30 min cycling on a cycle ergometer. The intensity of training corresponded to the subjects anaerobic threshold (4 to 6 mmol capillary lactate). Biochemical and histochemical analyses will contribute to our understandings by which exposure to hypoxia and nitrate consumption interact withmuscular adaptations to endurance training.status: publishe