Increasing maximal heart rate increases maximal O2 uptake in rats acclimatized to simulated altitude

Journal of Applied Physiology
N C GonzalezJ P Richalet

Abstract

Maximal exercise heart rate (HRmax) is reduced after acclimatization to hypobaric hypoxia. The low HRmax contributes to reduce maximal cardiac output (Qmax) and may limit maximal O2 uptake (VO2max). The objective of these experiments was to test the hypothesis that the reduction in Qmax after acclimatization to hypoxia, due, in part, to the low HRmax, limits VO2max. If this hypothesis is correct, an increase in Qmax would result in a proportionate increase in VO2max. Rats acclimatized to hypobaric hypoxia [inspired PO2 (PIO2) = 69.8 +/- 3 Torr for 3 wk] exercised on a treadmill in hypoxic (PIO2 = 71.7 +/- 1.1 Torr) or normoxic conditions (PIO2 = 142.1 +/- 1.1 Torr). Each rat ran twice: in one bout the rat was allowed to reach its spontaneous HRmax, which was 505 +/- 7 and 501 +/- 5 beats/min in hypoxic and normoxic exercise, respectively; in the other exercise bout, HRmax was increased by 20% to the preacclimatization value of 600 beats/min by atrial pacing. This resulted in an approximately 10% increase in Qmax, since the increase in HRmax was offset by a 10% decrease in stroke volume, probably due to shortening of diastolic filling time. The increase in Qmax was accompanied by a proportionate increase in maximal rate of conve...Continue Reading

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Citations

Nov 24, 1999·Journal of Applied Physiology·J G WoodN C Gonzalez
Oct 24, 2015·Journal of Applied Physiology·Hans Kristian StadheimJørgen Jensen
Aug 25, 2012·European Journal of Applied Physiology·Keyne CharlotDidier Chapelot
Feb 15, 2001·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·F FavretN C Gonzalez
Jul 2, 2003·Journal of Applied Physiology·Fabrice FavretNorberto C Gonzalez
Oct 22, 2002·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·J A L CalbetB Saltin
Jul 11, 2012·Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology·Stanley S HillmanMichael S Hedrick
Dec 5, 2013·Physiological Reports·Aurélien PichonRi-Li Ge
Nov 3, 2011·Journal of Physiology and Biochemistry·Aritz UrdampilletaJ Alfredo Martínez
Sep 6, 2011·Experimental Physiology·Cenk AydinChristopher J Gordon
Nov 25, 2020·Annual Review of Animal Biosciences·Jay F Storz, Zachary A Cheviron
Mar 23, 2021·Molecular Biology and Evolution·Jay F Storz
May 28, 2019·Metabolism: Clinical and Experimental·Melissa A LindenWilliam P Esler
Dec 18, 2007·The Journal of Experimental Biology·Gregory A RussellKimberly A Hammond
May 12, 2004·Respiratory Physiology & Neurobiology·Ewald R WeibelHans Hoppeler
May 25, 2007·Respiratory Physiology & Neurobiology·Fabrice Favret, Jean-Paul Richalet

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