AltitudeOmics: Effects of 16 Days Acclimatization to Hypobaric Hypoxia on Muscle Oxygen Extraction During Incremental Exercise

Overview

Journal J Appl Physiol (1985)

Publisher American Physiological Society

Date 2023 Aug 17

PMID 37589059

Authors

Nicolas Bourdillon

Andrew W Subudhi

Jui-Lin Fan

Oghenero Evero

Jonathan E Elliott

Andrew T Lovering

Robert C Roach

Bengt Kayser

Affiliations

Soon will be listed here.

Abstract

Acute altitude exposure lowers arterial oxygen content ([Formula: see text]) and cardiac output ([Formula: see text]) at peak exercise, whereas O extraction from blood to working muscles remains similar. Acclimatization normalizes [Formula: see text] but not peak [Formula: see text] nor peak oxygen consumption (V̇o). To what extent acclimatization impacts muscle O extraction remains unresolved. Twenty-one sea-level residents performed an incremental cycling exercise to exhaustion near sea level (SL), in acute (ALT1) and chronic (ALT16) hypoxia (5,260 m). Arterial blood gases, gas exchange at the mouth and oxy- (OHb) and deoxyhemoglobin (HHb) of the vastus lateralis were recorded to assess arterial O content ([Formula: see text]), [Formula: see text], and V̇o. The HHb-V̇o slope was taken as a surrogate for muscle O extraction. During moderate-intensity exercise, HHb-V̇o slope increased to a comparable extent at ALT1 (2.13 ± 0.94) and ALT16 (2.03 ± 0.88) compared with SL (1.27 ± 0.12), indicating increased O extraction. However, the HHb/[Formula: see text] ratio increased from SL to ALT1 and then tended to go back to SL values at ALT16. During high-intensity exercise, HHb-V̇o slope reached a break point beyond which it decreased at SL and ALT1, but not at ALT16. Increased muscle O extraction during submaximal exercise was associated with decreased [Formula: see text] in acute hypoxia. The significantly greater muscle O extraction during maximal exercise in chronic hypoxia is suggestive of an O reserve. During incremental exercise muscle deoxyhemoglobin (HHb) and oxygen consumption (V̇o) both increase linearly, and the slope of their relationship is an indirect index of local muscle O extraction. The latter was assessed at sea level, in acute and during chronic exposure to 5,260 m. The demonstrated presence of a muscle O extraction reserve during chronic exposure is coherent with previous studies indicating both limited muscle oxidative capacity and decrease in motor drive.

References

Amann M, Romer L, Subudhi A, Pegelow D, Dempsey J . Severity of arterial hypoxaemia affects the relative contributions of peripheral muscle fatigue to exercise performance in healthy humans. J Physiol. 2007; 581(Pt 1):389-403. PMC: 2075206. DOI: 10.1113/jphysiol.2007.129700. View

Koirala B, Concas A, Sun Y, Gladden L, Lai N . Relationship between muscle venous blood oxygenation and near-infrared spectroscopy: quantitative analysis of the Hb and Mb contributions. J Appl Physiol (1985). 2023; 134(5):1063-1074. PMC: 10125031. DOI: 10.1152/japplphysiol.00406.2022. View

Grensemann J . Cardiac Output Monitoring by Pulse Contour Analysis, the Technical Basics of Less-Invasive Techniques. Front Med (Lausanne). 2018; 5:64. PMC: 5845549. DOI: 10.3389/fmed.2018.00064. View

Kayser B . Exercise starts and ends in the brain. Eur J Appl Physiol. 2003; 90(3-4):411-9. DOI: 10.1007/s00421-003-0902-7. View

Boushel R, Langberg H, Olesen J, Bulow J, Kjaer M . Monitoring tissue oxygen availability with near infrared spectroscopy (NIRS) in health and disease. Scand J Med Sci Sports. 2001; 11(4):213-22. DOI: 10.1034/j.1600-0838.2001.110404.x. View

Murias J, Spencer M, Keir D, Paterson D . Systemic and vastus lateralis muscle blood flow and O2 extraction during ramp incremental cycle exercise. Am J Physiol Regul Integr Comp Physiol. 2013; 304(9):R720-5. PMC: 3652075. DOI: 10.1152/ajpregu.00016.2013. View

Ekblom B, Huot R, Stein E, Thorstensson A . Effect of changes in arterial oxygen content on circulation and physical performance. J Appl Physiol. 1975; 39(1):71-5. DOI: 10.1152/jappl.1975.39.1.71. View

Marcinek D, Amara C, Matz K, Conley K, Schenkman K . Wavelength shift analysis: a simple method to determine the contribution of hemoglobin and myoglobin to in vivo optical spectra. Appl Spectrosc. 2007; 61(6):665-9. DOI: 10.1366/000370207781269819. View

Horscroft J, Kotwica A, Laner V, West J, Hennis P, Levett D . Metabolic basis to Sherpa altitude adaptation. Proc Natl Acad Sci U S A. 2017; 114(24):6382-6387. PMC: 5474778. DOI: 10.1073/pnas.1700527114. View

10.

Subudhi A, Bourdillon N, Bucher J, Davis C, Elliott J, Eutermoster M . AltitudeOmics: the integrative physiology of human acclimatization to hypobaric hypoxia and its retention upon reascent. PLoS One. 2014; 9(3):e92191. PMC: 3962396. DOI: 10.1371/journal.pone.0092191. View

11.

Subudhi A, Olin J, Dimmen A, Polaner D, Kayser B, Roach R . Does cerebral oxygen delivery limit incremental exercise performance?. J Appl Physiol (1985). 2011; 111(6):1727-34. PMC: 3233884. DOI: 10.1152/japplphysiol.00569.2011. View

12.

Jacobs R, Siebenmann C, Hug M, Toigo M, Meinild A, Lundby C . Twenty-eight days at 3454-m altitude diminishes respiratory capacity but enhances efficiency in human skeletal muscle mitochondria. FASEB J. 2012; 26(12):5192-200. DOI: 10.1096/fj.12-218206. View

13.

Mollard P, Woorons X, Letournel M, Lamberto C, Favret F, Pichon A . Determinant factors of the decrease in aerobic performance in moderate acute hypoxia in women endurance athletes. Respir Physiol Neurobiol. 2007; 159(2):178-86. DOI: 10.1016/j.resp.2007.06.012. View

14.

Sutton J, Reeves J, Wagner P, GROVES B, Cymerman A, Malconian M . Operation Everest II: oxygen transport during exercise at extreme simulated altitude. J Appl Physiol (1985). 1988; 64(4):1309-21. DOI: 10.1152/jappl.1988.64.4.1309. View

15.

Subudhi A, Dimmen A, Roach R . Effects of acute hypoxia on cerebral and muscle oxygenation during incremental exercise. J Appl Physiol (1985). 2007; 103(1):177-83. DOI: 10.1152/japplphysiol.01460.2006. View

16.

Kayser B, Narici M, Binzoni T, Grassi B, Cerretelli P . Fatigue and exhaustion in chronic hypobaric hypoxia: influence of exercising muscle mass. J Appl Physiol (1985). 1994; 76(2):634-40. DOI: 10.1152/jappl.1994.76.2.634. View

17.

Lundby C, Pilegaard H, Andersen J, van Hall G, Sander M, Calbet J . Acclimatization to 4100 m does not change capillary density or mRNA expression of potential angiogenesis regulatory factors in human skeletal muscle. J Exp Biol. 2004; 207(Pt 22):3865-71. DOI: 10.1242/jeb.01225. View

18.

Wagner P . Determinants of maximal oxygen transport and utilization. Annu Rev Physiol. 1996; 58:21-50. DOI: 10.1146/annurev.ph.58.030196.000321. View

19.

Subudhi A, Lorenz M, Fulco C, Roach R . Cerebrovascular responses to incremental exercise during hypobaric hypoxia: effect of oxygenation on maximal performance. Am J Physiol Heart Circ Physiol. 2007; 294(1):H164-71. DOI: 10.1152/ajpheart.01104.2007. View

20.

Mollard P, Woorons X, Letournel M, Lamberto C, Favret F, Pichon A . Determinants of maximal oxygen uptake in moderate acute hypoxia in endurance athletes. Eur J Appl Physiol. 2007; 100(6):663-73. DOI: 10.1007/s00421-007-0457-0. View