Document Detail

Hyperventilation before resistance exercise: cerebral hemodynamics and orthostasis.
MedLine Citation:
PMID:  17762363     Owner:  NLM     Status:  MEDLINE    
Hyperventilation performed by athletes during preparation for resistance exercise might contribute to reports of postexercise orthostatic instability. PURPOSE: To test the hypothesis that post-resistance exercise orthostatic instability is associated with exaggerated reductions of cerebral blood-flow velocity after hyperventilation. METHODS: We recorded the ECG, end-tidal CO2, beat-by-beat finger arterial pressure, and cerebral blood-flow velocity in 10 healthy subjects. Subjects performed 10 repetitions of recumbent leg press using resistance equivalent to 80% of their six-repetition maximum during three separate trials (randomized): 1) no prior hyperventilation (NOHV); 2) after hyperventilation to an end-tidal CO2 of 3% (HV3%); and 3) after hyperventilation to an end-tidal CO2 of 2% (HV2%). After exercise, subjects stood upright for 10 s and rated symptoms of lightheadedness on a scale of 1 (none) to 5 (faint). RESULTS: Mean cerebral blood-flow velocity (CBFV(MEAN)) increased by 12% during exercise after NOHV and decreased by 14 and 25% during exercise after HV3% and HV2% (all P < 0.0001). During standing, mean arterial pressure (MAP) decreased by 96 mm Hg and CBFV(MEAN) decreased by 41 cm.s(-1) (pooled across conditions; all P < 0.0001). Absolute reductions of CBFV(MEAN) during standing were greater after HV2% compared with both NOHV and HV3% (P = 0.003). Ratings of perceived lightheadedness during standing increased with prior hyperventilation (P = 0.02) and correlated to the magnitude of reductions in MAP (r = 0.51; P = 0.003) and CBFV(MEAN) (r = 0.37; P = 0.04). CONCLUSIONS: Hyperventilation before lower-body resistance exercise exacerbates CBFV(MEAN) reductions during standing. Increased symptoms of orthostatic instability are associated with the magnitude of reductions in both MAP and CBFV(MEAN).
Steven A Romero; William H Cooke
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  39     ISSN:  0195-9131     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-08-31     Completed Date:  2007-10-30     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1302-7     Citation Subset:  IM; S    
Laboratory for Applied Autonomic Neurophysiology, The University of Texas at San Antonio, San Antonio, TX, USA.
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MeSH Terms
Blood Flow Velocity / physiology*
Brain / blood supply*
Dizziness / blood*
Hyperventilation / blood*
Weight Lifting / physiology*

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