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High Intensity Intervals Expand Plasma and Improves Exercise Performance in Acute Hypoxia
Author(s) -
Gillum Trevor,
Gorini Felipe
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.04239
Subject(s) - medicine , hypoxia (environmental) , plasma volume , hypervolemia , time trial , cardiology , blood volume , anesthesia , heart rate , blood pressure , chemistry , oxygen , organic chemistry
Hypoxia causes decrements in submaximal and maximal exercise performance. Hypervolemia may improve O 2 delivery to the metabolically active tissue, thus lowering physiological and cardiovascular strain during moderate exercise at altitude. Since significant time is needed to acclimate to exercise in hypoxia, we sought to expand plasma volume (PVE) through a single bout of high intensity intervals (HII) in an attempt to expedite improvements in aerobic performance. Purpose To determine if the hypervolemic response to a single bout of HII was sufficient to mitigate the hypoxia associated declines in exercise capacity. Methods In our randomized counterbalanced study, 7 males (24.4 ± 5.8 years, VO 2max 46.9 ± 5.8 ml kg −1 min −1 , 12.8 ± 4.4% body fat) performed two 15km cycling time‐trials (TTs) in normobaric hypoxia (FiO 2 = 15%) before and 48 hours following HII (8x4 minutes at 85% VO 2max with 4 minutes rest between rounds) or a control bout (CON) performed at 50% VO 2max , in which duration was extended to assure identical kilojoules completed between conditions. Pre‐exercise blood samples were collected to quantify changes in plasma volume, while hemodynamic data were collected utilizing PhysioFlow. Results Increased PVE was observed 24 hours (6.96% ± 4.84%) and 48 hours (9.77% ± 4.26%) (p<0.05) following HII while the CON condition decreased plasma volume 48 hours post (−3.75% ± 2.62%) (p<0.05). Under the HII condition, participants showed an improvement in TT performance (Time: 1880 ± 215s to 1840 ± 203s, Power: 164.8 ± 41.2W to 171 ± 39.5W) (p < 0.05) and lowered HR (164.5 ± 9.5 bpm to 161.9 ± 8.8 bpms) (p < 0.05). Stroke volume (SV) and cardiac output (Q) manifested an upwards trend during TT performance within the HI condition (p = 0.09 and p = 0.08, respectively). There was no difference in performance, Q, or SV in the CON condition. Hydration, RPE, SaO 2 , and blood lactate were similar in both TTs in hypoxia. Conclusion A single bout of HII resulted in increased cycling performance in acute hypoxia, accompanied by an enhanced PVE both 24 and 48 hours following exercise. This observed enhancement in cardiac efficiency following intense exercise may be desirable in military populations or individual needing to complete physical tasks at moderate altitude without the means or time to fully acclimatize.