Effects of altered FIO2 on maximum VO2 in the horse.
Abstract: Although the horse is considered an elite athlete with a specific VO2max some 2-4 times higher than man, maximal O2 transport is compromised both by moderately severe arterial desaturation and by failure to extract all O2 from blood perfusing exercising muscle. This prompted the present study to ascertain whether correction of arterial desaturation would proportionally augment VO2max and, if so, would O2 extraction behave in a manner predicted by diffusional transport limitation. Six two year old thoroughbreds were exercised to VO2max on a treadmill each on three separate occasions breathing gases of FIO2 = 0.15, 0.21 and 0.35, each used once in balanced order. VO2, ventilation, arterial and pulmonary arterial blood gases, pressures and lactate levels were measured both submaximally and maximally at each FIO2 and cardiac output was computed by mass balance for O2. At FIO2 = 0.21, VO2max = 143.9 +/- 4.8 ml kg-1 min-1, arterial saturation (SaO2) was 81.6 +/- 3.3% while venous PO2 (PvO2) was 15.3 +/- 1.4 Torr. At FIO2 = 0.35, VO2max was 172.6 +/- 8.2 ml kg-1 min-1, SaO2 reached 97.4 +/- 0.4% and PvO2 was 23.4 +/- 0.7 Torr. VO2max at FIO2 = 0.15 was 109.8 +/- 4.1 ml kg-1 min-1, SaO2 fell to 68.1 +/- 2.5% and PvO2 was 10.6 +/- 1.0 Torr, all changes being significant, p < 0.01. As FIO2 was varied, VO2max changed proportionally to calculated mean capillary Po2 as well as to total O2 delivery. These data confirm substantial O2 supply dependence of VO2max in the horse, and in such a manner as to be consistent with the hypothesis of combined diffusive and convective transport limitation within muscle.
Publication Date: 1996-08-01 PubMed ID: 8897658DOI: 10.1016/0034-5687(96)00044-8Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
- Animal Health
- Athletic Horses
- Athletic Performance
- Blood
- Cardiovascular Health
- Equine Diseases
- Equine Health
- Equine Science
- Exercise
- Exercise Physiology
- Horse Training
- Oxygen
- Performance Horses
- Physiology
- Respiratory Health
- Thoroughbreds
- Treadmill Exercise
- Veterinary Care
- Veterinary Medicine
- Veterinary Research
- VO2 Max
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
This research examines how varying levels of inhaled oxygen (FIO2) impact the VO2max, a measure of the maximum amount of oxygen an athlete can utilize during intense exercise, in horses. The study finds that altering FIO2 does significantly affect VO2max, suggesting oxygen supply plays a critical role in determining the maximum volume of oxygen that can be used during high-intensity exercise in horses.
Methodology
- The study involved six two-year-old thoroughbred horses that were exercised to their VO2max on a treadmill on three separate occasions under three different inhaled oxygen conditions (FIO2 = 0.15, 0.21, and 0.35). Each FIO2 level was used once in a balanced order.
- During the exercises, various parameters such as VO2 (oxygen consumption), ventilation, arterial and pulmonary arterial blood gases, pressures and lactate levels, and cardiac output were measured both sub-maximally and maximally at each FIO2 level.
Results
- In an atmosphere with normal oxygen levels (FIO2 = 0.21), the median VO2max was found to be 143.9 +/- 4.8 ml kg-1 min-1. However, the arterial oxygen saturation was only 81.6 +/- 3.3%, indicating some arterial desaturation.
- When the inhaled oxygen level was increased to 0.35, the median VO2max increased to 172.6 +/- 8.2 ml kg-1 min-1, with arterial oxygen saturation reaching 97.4 +/- 0.4%.
- In contrast, a decrease in FIO2 to 0.15 resulted in a reduced VO2max of 109.8 +/- 4.1 ml kg-1 min-1 and a lower arterial oxygen saturation of 68.1 +/- 2.5%.
- All changes were found to be significant and these results confirmed that VO2max had a substantial dependence on the oxygen supply in horses.
Conclusion
- The study thus concluded that altering the level of inhaled oxygen does have a significant impact on the maximum amount of oxygen a horse can use during intense exercise.
- These findings are consistent with the hypothesis of combined diffusive and convective transport limitation within muscle, suggesting that both the oxygen delivery method and the minimum oxygen diffusion capacity in the muscle tissue could influence VO2max.
Cite This Article
APA
Wagner PD, Erickson BK, Seaman J, Kubo K, Hiraga A, Kai M, Yamaya Y.
(1996).
Effects of altered FIO2 on maximum VO2 in the horse.
Respir Physiol, 105(1-2), 123-134.
https://doi.org/10.1016/0034-5687(96)00044-8 Publication
Researcher Affiliations
- Department of Medicine 0623A, University of California, San Diego, La Jolla 92093-0623, USA.
MeSH Terms
- Animals
- Blood Pressure
- Capillaries / physiology
- Carbon Dioxide / blood
- Cardiac Output / physiology
- Catheterization
- Convection
- Diffusion
- Hemodynamics
- Horses
- Hypoxia / metabolism
- Oxygen / blood
- Oxygen / metabolism
- Partial Pressure
- Physical Conditioning, Animal / physiology
- Respiration / physiology
- Respiratory Function Tests
- Vasoconstriction / physiology
Grant Funding
- HL17731 / NHLBI NIH HHS
Citations
This article has been cited 9 times.- Takahashi K, Mukai K, Takahashi Y, Ebisuda Y, Sugiyama F, Hatta H, Kitaoka Y. Effects of hypoxia and hyperoxia on exercise-induced metabolomic and transcriptomic profiles in equine skeletal muscle. J Exp Biol 2025 Dec 15;228(24).
- Ohmura H, Mukai K, Takahashi Y, Takahashi T. Metabolomic analysis of skeletal muscle before and after strenuous exercise to fatigue. Sci Rep 2021 May 27;11(1):11261.
- Ohmura H, Mukai K, Matsui A, Takahashi T, Jones JH. Cardiopulmonary function during supramaximal exercise in hypoxia, normoxia and hyperoxia in Thoroughbred horses. J Equine Sci 2020;31(4):67-73.
- Dempsey JA, La Gerche A, Hull JH. Is the healthy respiratory system built just right, overbuilt, or underbuilt to meet the demands imposed by exercise?. J Appl Physiol (1985) 2020 Dec 1;129(6):1235-1256.
- Mukai K, Ohmura H, Matsui A, Aida H, Takahashi T, Jones JH. High-intensity training in normobaric hypoxia enhances exercise performance and aerobic capacity in Thoroughbred horses: A randomized crossover study. Physiol Rep 2020 May;8(10):e14442.
- Birks EK, Ohmura H, Jones JH. Measuring V̇O(2) in hypoxic and hyperoxic conditions using dynamic gas mixing with a flow-through indirect calorimeter. J Equine Sci 2019;30(4):87-92.
- Ohmura H, Mukai K, Takahashi Y, Takahashi T, Jones JH. Hypoxic training increases maximal oxygen consumption in Thoroughbred horses well-trained in normoxia. J Equine Sci 2017;28(2):41-45.
- Ferretti G. Maximal oxygen consumption in healthy humans: theories and facts. Eur J Appl Physiol 2014 Oct;114(10):2007-36.
- Schuler B, Arras M, Keller S, Rettich A, Lundby C, Vogel J, Gassmann M. Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice. Proc Natl Acad Sci U S A 2010 Jan 5;107(1):419-23.
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