Vagal Threshold Determination during Incremental Stepwise Exercise in Normoxia and Normobaric Hypoxia

Filip Neuls, Jakub Krejci, Ales Jakubec, Michal Botek and Michal Valenta
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Filip Neuls: Department of Natural Sciences in Kinanthropology, Faculty of Physical Culture, Palacky University Olomouc, 771 11 Olomouc, Czech Republic
Jakub Krejci: Department of Natural Sciences in Kinanthropology, Faculty of Physical Culture, Palacky University Olomouc, 771 11 Olomouc, Czech Republic
Ales Jakubec: Department of Natural Sciences in Kinanthropology, Faculty of Physical Culture, Palacky University Olomouc, 771 11 Olomouc, Czech Republic
Michal Botek: Department of Natural Sciences in Kinanthropology, Faculty of Physical Culture, Palacky University Olomouc, 771 11 Olomouc, Czech Republic
Michal Valenta: Department of Natural Sciences in Kinanthropology, Faculty of Physical Culture, Palacky University Olomouc, 771 11 Olomouc, Czech Republic

IJERPH, 2020, vol. 17, issue 20, 1-12

Abstract: This study focuses on the determination of the vagal threshold (T va ) during exercise with increasing intensity in normoxia and normobaric hypoxia. The experimental protocol was performed by 28 healthy men aged 20 to 30 years. It included three stages of exercise on a bicycle ergometer with a fraction of inspired oxygen (FiO 2 ) 20.9% (normoxia), 17.3% (simulated altitude ~1500 m), and 15.3% (~2500 m) at intensity associated with 20% to 70% of the maximal heart rate reserve (MHRR) set in normoxia. T va level in normoxia was determined at exercise intensity corresponding with (M ± SD) 45.0 ± 5.6% of MHRR. Power output at T va (PO th ), representing threshold exercise intensity, decreased with increasing degree of hypoxia (normoxia: 114 ± 29 W; FiO 2 = 17.3%: 110 ± 27 W; FiO 2 = 15.3%: 96 ± 32 W). Significant changes in PO th were observed with FiO 2 = 15.3% compared to normoxia ( p = 0.007) and FiO 2 = 17.3% ( p = 0.001). Consequentially, normoxic %MHRR adjusted for hypoxia with FiO 2 = 15.3% was reduced to 39.9 ± 5.5%. Considering the convenient altitude for exercise in hypoxia, PO th did not differ excessively between normoxic conditions and the simulated altitude of ~1500 m, while more substantial decline of PO th occurred at the simulated altitude of ~2500 m compared to the other two conditions.

Keywords: autonomic nervous system; vagal withdrawal; simulated altitude; exercise intensity; saturation (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
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