Document Detail

Thigh oxygen uptake at the onset of intense exercise is not affected by a reduction in oxygen delivery caused by hypoxia.
MedLine Citation:
PMID:  22933023     Owner:  NLM     Status:  Publisher    
In response to hypoxic breathing most studies report slower pulmonary oxygen uptake (VO(2)) kinetics at the onset of exercise, but it is not known if this relates to an actual slowing of the VO(2) in the active muscles. The aim of the present study was to evaluate whether thigh VO(2) is slowed at the onset of intense exercise during acute exposure to hypoxia. Six healthy male subjects (25.8±1.4 years, 79.8±4.0 kg, mean±SEM) performed intense (100±6 W) two-legged knee-extensor exercise for 2 min in normoxia (NOR) and hypoxia (F(i)O(2)=0.13; HYP). Thigh VO(2) was measured by frequent arterial and venous blood sampling and blood flow measurements. In arterial blood, oxygen content was reduced (P<0.05) from 191±5 mL O(2)/L in NOR to 180±5 mL O(2)/L in HYP, and oxygen pressure was reduced (P<0.001) from 111±4 mmHg in NOR to 63±4 mmHg in HYP. Thigh blood flow was the same in NOR and HYP and thigh oxygen delivery was consequently reduced (P<0.05) in HYP, but femoral arterial-venous oxygen difference and thigh VO(2) were similar in NOR and HYP. In addition, muscle lactate release was the same in NOR and HYP and muscle lactate accumulation during the first 25 s of exercise determined from muscle biopsy sampling was also similar (0.35±0.07 and 0.36±0.07 mmol/kg dw/s in NOR and HYP). Thus, the increase in thigh VO(2) was not attenuated at the onset of intense knee-extensor exercise despite a reduction in oxygen delivery and pressure.
Peter Moller Christensen; Nikolai Baastrup Nordsborg; Lars Nybo Nielsen; Stefan P Mortensen; Mikael Sander; Niels H Secher; Jens Bangsbo
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-8-29
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  -     ISSN:  1522-1490     ISO Abbreviation:  Am. J. Physiol. Regul. Integr. Comp. Physiol.     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-8-30     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1University of Copenhagen.
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