Document Detail


Alkalosis increases muscle K+ release, but lowers plasma [K+] and delays fatigue during dynamic forearm exercise.
MedLine Citation:
PMID:  16239279     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Alkalosis enhances human exercise performance, and reduces K+ loss in contracting rat muscle. We investigated alkalosis effects on K+ regulation, ionic regulation and fatigue during intense exercise in nine untrained volunteers. Concentric finger flexions were conducted at 75% peak work rate (3 W) until fatigue, under alkalosis (Alk, NaHCO3, 0.3 g kg(-1)) and control (Con, CaCO3) conditions, 1 month apart in a randomised, double-blind, crossover design. Deep antecubital venous (v) and radial arterial (a) blood was drawn at rest, during exercise and recovery, to determine arterio-venous differences for electrolytes, fluid shifts, acid-base and gas exchange. Finger flexion exercise barely perturbed arterial plasma ions and acid-base status, but induced marked arterio-venous changes. Alk elevated [HCO3-] and PCO2, and lowered [H+] (P < 0.05). Time to fatigue increased substantially during Alk (25 +/- 8%, P < 0.05), whilst both [K+]a and [K+]v were reduced (P < 0.01) and [K+]a-v during exercise tended to be greater (P= 0.056, n= 8). Muscle K+ efflux at fatigue was greater in Alk (21.2+/- 7.6 micromol min(-1), 32 +/- 7%, P < 0.05, n= 6), but peak K+ uptake rate was elevated during recovery (15 +/- 7%, P < 0.05) suggesting increased muscle Na+,K+-ATPase activity. Alk induced greater [Na+]a, [Cl-]v, muscle Cl- influx and muscle lactate concentration ([Lac-]) efflux during exercise and recovery (P < 0.05). The lower circulating [K+] and greater muscle K+ uptake, Na+ delivery and Cl- uptake with Alk, are all consistent with preservation of membrane excitability during exercise. This suggests that lesser exercise-induced membrane depolarization may be an important mechanism underlying enhanced exercise performance with Alk. Thus Alk was associated with improved regulation of K+, Na+, Cl- and Lac-.
Authors:
Simon M Sostaric; Sandford L Skinner; Malcolm J Brown; Termboon Sangkabutra; Ivan Medved; Tanya Medley; Steve E Selig; Ian Fairweather; Danny Rutar; Michael J McKenna
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Publication Detail:
Type:  Journal Article     Date:  2005-10-20
Journal Detail:
Title:  The Journal of physiology     Volume:  570     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2006 Jan 
Date Detail:
Created Date:  2006-01-02     Completed Date:  2006-05-08     Revised Date:  2013-06-07    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  185-205     Citation Subset:  IM    
Affiliation:
Muscle, Ions and Exercise Group, Centre for Ageing, Rehabilitation, Exercise and Sport, School of Human Movement, Recreation and Performance, Victoria University, Melbourne, Victoria, Australia.
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MeSH Terms
Descriptor/Qualifier:
Alkalosis / blood,  physiopathology*
Chlorides / blood
Exercise / physiology*
Exercise Test
Female
Forearm
Humans
Male
Muscle Fatigue / physiology*
Muscle, Skeletal / metabolism
Potassium / blood*
Sodium / blood
Time Factors
Chemical
Reg. No./Substance:
0/Chlorides; 7440-09-7/Potassium; 7440-23-5/Sodium
Comments/Corrections

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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