Document Detail

Human muscle net K(+) release during exercise is unaffected by elevated anaerobic metabolism, but reduced after prolonged acclimatization to 4,100 m.
MedLine Citation:
PMID:  20410475     Owner:  NLM     Status:  MEDLINE    
It was investigated whether skeletal muscle K(+) release is linked to the degree of anaerobic energy production. Six subjects performed an incremental bicycle exercise test in normoxic and hypoxic conditions prior to and after 2 and 8 wk of acclimatization to 4,100 m. The highest workload completed by all subjects in all trials was 260 W. With acute hypoxic exposure prior to acclimatization, venous plasma [K(+)] was lower (P < 0.05) in normoxia (4.9 +/- 0.1 mM) than hypoxia (5.2 +/- 0.2 mM) at 260 W, but similar at exhaustion, which occurred at 400 +/- 9 W and 307 +/- 7 W (P < 0.05), respectively. At the same absolute exercise intensity, leg net K(+) release was unaffected by hypoxic exposure independent of acclimatization. After 8 wk of acclimatization, no difference existed in venous plasma [K(+)] between the normoxic and hypoxic trial, either at submaximal intensities or at exhaustion (360 +/- 14 W vs. 313 +/- 8 W; P < 0.05). At the same absolute exercise intensity, leg net K(+) release was less (P < 0.001) than prior to acclimatization and reached negative values in both hypoxic and normoxic conditions after acclimatization. Moreover, the reduction in plasma volume during exercise relative to rest was less (P < 0.01) in normoxic than hypoxic conditions, irrespective of the degree of acclimatization (at 260 W prior to acclimatization: -4.9 +/- 0.8% in normoxia and -10.0 +/- 0.4% in hypoxia). It is concluded that leg net K(+) release is unrelated to anaerobic energy production and that acclimatization reduces leg net K(+) release during exercise.
Nikolai B Nordsborg; José A L Calbet; Mikael Sander; Gerrit van Hall; Carsten Juel; Bengt Saltin; Carsten Lundby
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Publication Detail:
Type:  Journal Article     Date:  2010-04-21
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  299     ISSN:  1522-1490     ISO Abbreviation:  Am. J. Physiol. Regul. Integr. Comp. Physiol.     Publication Date:  2010 Jul 
Date Detail:
Created Date:  2010-06-25     Completed Date:  2010-07-08     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  R306-13     Citation Subset:  IM    
Copenhagen Muscle Research Center, Rigshospitalet Section, Copenhagen Ø, Denmark.
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MeSH Terms
Acclimatization / physiology*
Anoxia / metabolism*
Blood Volume
Exercise / physiology*
Exercise Test
Fatigue / metabolism
Muscle, Skeletal / metabolism*
Muscles / metabolism
Plasma Volume

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