Document Detail

Effect of acute hypoxia on muscle blood flow, VO(2p), and [HHb] kinetics during leg extension exercise in older men.
MedLine Citation:
PMID:  23381722     Owner:  NLM     Status:  Publisher    
The adjustment of pulmonary oxygen uptake (VO(2p)), heart rate (HR), limb blood flow (LBF), and muscle deoxygenation [HHb] was examined during the transition to moderate-intensity, knee-extension exercise in six older adults (70 ± 4 years) under two conditions: normoxia (FIO(2) = 20.9 %) and hypoxia (FIO(2) = 15 %). The subjects performed repeated step transitions from an active baseline (3 W) to an absolute work rate (21 W) in both conditions. Phase 2 VO(2p), HR, LBF, and [HHb] data were fit with an exponential model. Under hypoxic conditions, no change was observed in HR kinetics, on the other hand, LBF kinetics was faster (normoxia 34 ± 3 s; hypoxia 28 ± 2), whereas the overall [HHb] adjustment ([Formula: see text]) was slower (normoxia 28 ± 2; hypoxia 33 ± 4 s). Phase 2 VO(2p) kinetics were unchanged (p < 0.05). The faster LBF kinetics and slower [HHb] kinetics reflect an improved matching between O(2) delivery and O(2) utilization at the microvascular level, preventing the phase 2 VO(2p) kinetics from become slower in hypoxia. Moreover, the absolute blood flow values were higher in hypoxia (1.17 ± 0.2 L min(-1)) compared to normoxia (0.96 ± 0.2 L min(-1)) during the steady-state exercise at 21 W. These findings support the idea that, for older adults exercising at a low work rate, an increase of limb blood flow offsets the drop in arterial oxygen content (CaO(2)) caused by breathing an hypoxic mixture.
Livio Zerbini; Matthew D Spencer; Tyler M Grey; Juan M Murias; John M Kowalchuk; Federico Schena; Donald H Paterson
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-2-5
Journal Detail:
Title:  European journal of applied physiology     Volume:  -     ISSN:  1439-6327     ISO Abbreviation:  Eur. J. Appl. Physiol.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-2-5     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100954790     Medline TA:  Eur J Appl Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
CeRiSM, Centre of Sport Health and Mountain, Rovereto, Italy.
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