Document Detail

Effect of hypoxia on the dynamic response of hyperaemia in the contracting human calf muscle.
MedLine Citation:
PMID:  22689444     Owner:  NLM     Status:  Publisher    
Although systemic hypoxia increases the muscle hyperaemic response during 'steady-state' exercise, its effect on dynamic characteristics of this response is not clear. In the present study we first established that hypoxia increases the steady-state hyperaemic response at low workloads during calf exercise. To study dynamic aspects of this response, eight subjects performed eight exercise trials while breathing a normoxic (FIO2 = 0.2094) or hypoxic (FIO2 = 0.105) gas mixture. Subjects performed intermittent contractions (1 s) of the calf muscle at 20 %MVC and leg blood flow (LBF), leg vascular conductance (LVC) and EMG activities of the triceps surae muscles were measured during each contraction-relaxation period (3 s). LBF and LVC responses were averaged for each subject and fitted using a four-phase, exponential, growth and decay function. Hypoxia evoked significant increases in the change in LBF (15 %) and LVC (23 %) from the start to end of exercise, as well as the amplitude of the rapid growth phase of LBF and LVC (21 %). Similar, but nonsignificant, effects on the amplitude of the slow growth phase of LBF (P = 0.08) and LVC (P = 0.10) were observed. By contrast, hypoxia had no effect on temporal parameters of these growth phases, parameter defining the decay phases, or EMG activities. These results suggest that the effect of hypoxia on exercise hyperaemia is targeted at the rapid and perhaps slow growth phase of the response, and is not mediated by a change in the level of muscle activation.
Joseph Donnelly; Simon Green
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-6-11
Journal Detail:
Title:  Experimental physiology     Volume:  -     ISSN:  1469-445X     ISO Abbreviation:  -     Publication Date:  2012 Jun 
Date Detail:
Created Date:  2012-6-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1 University of Otago;
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