Effects of altered FiO2 on maximum V̇O2 in the horse

Wagner, Peter D.; Erickson, B. K.; Seaman, J.; Kubo, Katsuyoshi; Hiraga, Atsushi; Kai, Makoto; Yamaya, Yoshiki

doi:10.1016/0034-5687(96)00044-8

Cited by 29 publications

(31 citation statements)

References 18 publications

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“…This mechanism elevates the blood O 2 -carrying capacity during exercise within seconds. As a consequence, Htc increases from ≈0.4 at rest to ≈0.6 at exercise (28,29) facilitating an improvement in exercise performance. These hematopoietic parameters return quickly to resting values when the animals stop exercising, preventing a constant overload of the cardiovascular system (28)(29)(30).…”

Section: Discussionmentioning

confidence: 99%

“…As a consequence, Htc increases from ≈0.4 at rest to ≈0.6 at exercise (28,29) facilitating an improvement in exercise performance. These hematopoietic parameters return quickly to resting values when the animals stop exercising, preventing a constant overload of the cardiovascular system (28)(29)(30). In light of our data, it is tempting to speculate that horses and dogs temporarily elevate their Htc levels close to the optimal value Htc to reach maximal systemic endurance performance.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

Schuler

Arras

Keller

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

100

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Erythropoietin (Epo) treatment increases hematocrit (Htc) and, consequently, arterial O 2 content. This in turn improves exercise performance. However, because elevated blood viscosity associated with increasing Htc levels may limit cardiac performance, it was suggested that the highest attainable Htc may not necessarily be associated with the highest attainable exercise capacity. To test the proposed hypothesis that an optimal Htc in acute and chronic Epotreated mice exists-i.e., the Htc that facilitates the greatest O 2 flux during maximal exercise-Htc levels of wild-type mice were acutely elevated by administering novel erythropoiesis-stimulating protein (NESP; wtNESP). Furthermore, in the transgenic mouse line tg6 that reaches Htc levels of up to 0.9 because of constitutive overexpression of human Epo, the Htc was gradually reduced by application of the hemolysis-inducing compound phenylhydrazine (PHZ; tg6PHZ). Maximal cardiovascular performance was measured by using telemetry in all exercising mice. Highest maximal O 2 uptake ( _ VO 2max ) and maximal time to exhaustion at submaximal exercise intensities were reached at Htc values of 0.58 and 0.57 for wtNESP, and 0.68 and 0.66 for tg6PHZ, respectively. Rate pressure product, and thus also maximal working capacity of the heart, increased with elevated Htc values. Blood viscosity correlated with _ VO 2max . Apart from the confirmation of the Htc hypothesis, we conclude that tg6PHZ adapted better to varying Htc values than wtNESP because of the higher optimal Htc of tg6PHZ compared to wtNESP. Of note, blood viscosity plays a critical role in limiting exercise capacity.blood viscosity | doping | excessive erythrocytosis | exercise performance | hemolysis

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

Schuler

Arras

Keller

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

100

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“…It has been reported that Thoroughbred horses experience severe hypoxemia when exercising at V̇O 2 max, with arterial O 2 tension less than 75 mmHg [3, 14, 15, 22]. Therefore, we wonder if hypoxic training would be effective for increasing V̇O 2 max and the performance of well-trained Thoroughbred horses.…”

mentioning

confidence: 98%

Hypoxic training increases maximal oxygen consumption in Thoroughbred horses well-trained in normoxia

Ohmura

Mukai

Takahashi

et al. 2017

JES

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Hypoxic training is effective for improving athletic performance in humans. It increases maximal oxygen consumption (V̇O2max) more than normoxic training in untrained horses. However, the effects of hypoxic training on well-trained horses are unclear. We measured the effects of hypoxic training on V̇O2max of 5 well-trained horses in which V̇O2max had not increased over 3 consecutive weeks of supramaximal treadmill training in normoxia which was performed twice a week. The horses trained with hypoxia (15% inspired O2) twice a week. Cardiorespiratory valuables were analyzed with analysis of variance between before and after 3 weeks of hypoxic training. Mass-specific V̇O2max increased after 3 weeks of hypoxic training (178 ± 10 vs. 194 ± 12.3 ml O2 (STPD)/(kg × min), P<0.05) even though all-out training in normoxia had not increased V̇O2max. Absolute V̇O2max also increased after hypoxic training (86.6 ± 6.2 vs. 93.6 ± 6.6 l O2 (STPD)/min, P<0.05). Total running distance after hypoxic training increased 12% compared to that before hypoxic training; however, the difference was not significant. There were no significant differences between pre- and post-hypoxic training for end-run plasma lactate concentrations or packed cell volumes. Hypoxic training may increase V̇O2max even though it is not increased by normoxic training in well-trained horses, at least for the durations of time evaluated in this study. Training while breathing hypoxic gas may have the potential to enhance normoxic performance of Thoroughbred horses.

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“…Many review articles were published ever since on specific subjects such as _ V O 2 max (see e.g. Saltin and Strange 1992;Taylor 1987;Wagner 1996), the exercise transients (Grassi 2000;Jones and Poole 2005;Whipp and Ward 1990), the effects of training (Fluck 2006;Maughan et al 1997), anaerobic metabolisms (di Prampero and, the energetics of human locomotion (di Prampero 2000; Zamparo et al 2011) or the cardiovascular responses to exercise (Fadel 2008;Joyner 2006;Laughlin 1999;Rowell and O'Leary 1990). New aspects were investigated, such as the effects of extreme environments or of ageing.…”

Section: The Perspective Of This Bookmentioning

confidence: 99%

“…Richardson et al (1999) were able to observe a _ V O 2max increase during single-leg exercise only when they used pure oxygen breathing. The thoroughbred horse, a highly athletic animal characterized by deep hypoxaemia at maximal exercise, was proposed as the nicest example supporting the prediction of elevated _ V O 2max in hyperoxia (Wagner 1996a;Wagner et al 1989Wagner et al , 1996. This apparent discrepancy between theoretical predictions and experimental data is hard to explain, and the hypotheses put forward so far are scarcely convincing, so that the issue still remains open.…”

Section: Experimental Testing Of Wagner's Modelmentioning

confidence: 99%

Energetics of Muscular Exercise

Ferretti¹

2015

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Effects of altered FiO2 on maximum V̇O2 in the horse

Cited by 29 publications

References 18 publications

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

Hypoxic training increases maximal oxygen consumption in Thoroughbred horses well-trained in normoxia

Energetics of Muscular Exercise

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