On the mechanisms that limit oxygen uptake during exercise in acute and chronic hypoxia: role of muscle mass
(2009) In Journal of Physiology 587(2). p.477-490- Abstract
- Peak aerobic power in humans ((V) over dot(O2), peak) is markedly affected by inspired O-2 tension (F-IO2). The question to be answered in this study is what factor plays a major role in the limitation of muscle peak. (V) over dot(O2) in hypoxia: arterial O-2 partial pressure (P-a,(O2)) or O-2 content (C-a,C-O2)? Thus, cardiac output (dye dilution with Cardio-green), leg blood flow (thermodilution), intra-arterial blood pressure and femoral arterial-to-venous differences in blood gases were determined in nine lowlanders studied during incremental exercise using a large (two-legged cycle ergometer exercise: Bike) and a small (one-legged knee extension exercise: Knee) muscle mass in normoxia, acute hypoxia (AH) (F-IO2 = 0.105) and after 9... (More)
- Peak aerobic power in humans ((V) over dot(O2), peak) is markedly affected by inspired O-2 tension (F-IO2). The question to be answered in this study is what factor plays a major role in the limitation of muscle peak. (V) over dot(O2) in hypoxia: arterial O-2 partial pressure (P-a,(O2)) or O-2 content (C-a,C-O2)? Thus, cardiac output (dye dilution with Cardio-green), leg blood flow (thermodilution), intra-arterial blood pressure and femoral arterial-to-venous differences in blood gases were determined in nine lowlanders studied during incremental exercise using a large (two-legged cycle ergometer exercise: Bike) and a small (one-legged knee extension exercise: Knee) muscle mass in normoxia, acute hypoxia (AH) (F-IO2 = 0.105) and after 9 weeks of residence at 5260 m (CH). Reducing the size of the active muscle mass blunted by 62% the effect of hypoxia on. (V) over dot(O2,peak) in AH and abolished completely the effect of hypoxia on. (V) over dot(O2,peak) after altitude acclimatization. Acclimatization improved Bike peak exercise Pa, O-2 from 34 +/- 1 in AH to 45 +/- 1 mmHg in CH(P < 0.05) and Knee Pa, O-2 from 38 +/- 1 to 55 +/- 2 mmHg(P < 0.05). Peak cardiac output and leg blood flow were reduced in hypoxia only during Bike. Acute hypoxia resulted in reduction of systemic O-2 delivery (46 and 21%) and leg O-2 delivery (47 and 26%) during Bike and Knee, respectively, almost matching the corresponding reduction in. (V) over dot(O2,peak). Altitude acclimatization restored fully peak systemic and leg O-2 delivery in CH (2.69 +/- 0.27 and 1.28 +/- 0.11 l min(-1), respectively) to sea level values (2.65 +/- 0.15 and 1.16 +/- 0.11 l min(-1), respectively) during Knee, but not during Bike. During Knee in CH, leg oxygen delivery was similar to normoxia and, therefore, also. (V) over dot(O2,peak) in spite of a P-a,P-O2 of 55 mmHg. Reducing the size of the active muscle mass improves pulmonary gas exchange during hypoxic exercise, attenuates the Bohr effect on oxygen uploading at the lungs and preserves sea level convective O-2 transport to the active muscles. Thus, the altitude-acclimatized human has potentially a similar exercising capacity as at sea level when the exercise model allows for an adequate oxygen delivery (blood flow x C-a,C-O2), with only a minor role of P-a,P-O2 per se, when P-a,P-O2 is more than 55 mmHg. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1312517
- author
- Calbet, Jose A. L. ; Rådegran, Göran LU ; Boushel, Robert and Saltin, Bengt
- organization
- publishing date
- 2009
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Journal of Physiology
- volume
- 587
- issue
- 2
- pages
- 477 - 490
- publisher
- The Physiological Society
- external identifiers
-
- wos:000262488200016
- scopus:58349087882
- pmid:19047206
- ISSN
- 1469-7793
- DOI
- 10.1113/jphysiol.2008.162271
- language
- English
- LU publication?
- yes
- id
- a11939f3-8742-481b-904a-a7277e178646 (old id 1312517)
- date added to LUP
- 2016-04-01 14:25:46
- date last changed
- 2022-02-12 02:34:49
@article{a11939f3-8742-481b-904a-a7277e178646,
abstract = {{Peak aerobic power in humans ((V) over dot(O2), peak) is markedly affected by inspired O-2 tension (F-IO2). The question to be answered in this study is what factor plays a major role in the limitation of muscle peak. (V) over dot(O2) in hypoxia: arterial O-2 partial pressure (P-a,(O2)) or O-2 content (C-a,C-O2)? Thus, cardiac output (dye dilution with Cardio-green), leg blood flow (thermodilution), intra-arterial blood pressure and femoral arterial-to-venous differences in blood gases were determined in nine lowlanders studied during incremental exercise using a large (two-legged cycle ergometer exercise: Bike) and a small (one-legged knee extension exercise: Knee) muscle mass in normoxia, acute hypoxia (AH) (F-IO2 = 0.105) and after 9 weeks of residence at 5260 m (CH). Reducing the size of the active muscle mass blunted by 62% the effect of hypoxia on. (V) over dot(O2,peak) in AH and abolished completely the effect of hypoxia on. (V) over dot(O2,peak) after altitude acclimatization. Acclimatization improved Bike peak exercise Pa, O-2 from 34 +/- 1 in AH to 45 +/- 1 mmHg in CH(P < 0.05) and Knee Pa, O-2 from 38 +/- 1 to 55 +/- 2 mmHg(P < 0.05). Peak cardiac output and leg blood flow were reduced in hypoxia only during Bike. Acute hypoxia resulted in reduction of systemic O-2 delivery (46 and 21%) and leg O-2 delivery (47 and 26%) during Bike and Knee, respectively, almost matching the corresponding reduction in. (V) over dot(O2,peak). Altitude acclimatization restored fully peak systemic and leg O-2 delivery in CH (2.69 +/- 0.27 and 1.28 +/- 0.11 l min(-1), respectively) to sea level values (2.65 +/- 0.15 and 1.16 +/- 0.11 l min(-1), respectively) during Knee, but not during Bike. During Knee in CH, leg oxygen delivery was similar to normoxia and, therefore, also. (V) over dot(O2,peak) in spite of a P-a,P-O2 of 55 mmHg. Reducing the size of the active muscle mass improves pulmonary gas exchange during hypoxic exercise, attenuates the Bohr effect on oxygen uploading at the lungs and preserves sea level convective O-2 transport to the active muscles. Thus, the altitude-acclimatized human has potentially a similar exercising capacity as at sea level when the exercise model allows for an adequate oxygen delivery (blood flow x C-a,C-O2), with only a minor role of P-a,P-O2 per se, when P-a,P-O2 is more than 55 mmHg.}},
author = {{Calbet, Jose A. L. and Rådegran, Göran and Boushel, Robert and Saltin, Bengt}},
issn = {{1469-7793}},
language = {{eng}},
number = {{2}},
pages = {{477--490}},
publisher = {{The Physiological Society}},
series = {{Journal of Physiology}},
title = {{On the mechanisms that limit oxygen uptake during exercise in acute and chronic hypoxia: role of muscle mass}},
url = {{http://dx.doi.org/10.1113/jphysiol.2008.162271}},
doi = {{10.1113/jphysiol.2008.162271}},
volume = {{587}},
year = {{2009}},
}