Document Detail

Muscle metabolism during constant- and alternating-intensity exercise around critical power.
MedLine Citation:
PMID:  17024627     Owner:  NLM     Status:  MEDLINE    
Few studies have focused on the metabolic responses to alternating high- and low-intensity exercise and, specifically, compared these responses to those seen during constant-load exercise performed at the same average power output. This study compared muscle metabolic responses between two patterns of exercise during which the intensity was either constant and just below critical power (CP) or that oscillated above and below CP. Six trained males (mean +/- SD age 23.6 +/- 2.6 y) completed two 30-minute bouts of cycling (alternating and constant) at an average intensity equal to 90 % of CP. The intensity during alternating exercise varied between 158 % CP and 73 % CP. Biopsy samples from the vastus lateralis muscle were taken before (PRE), at the midpoint and end (POST) of exercise and analysed for glycogen, lactate, PCr and pH. Although these metabolic variables in muscle changed significantly during both patterns of exercise, there were no significant differences (p > 0.05) between constant and alternating exercise for glycogen (PRE: 418.8 +/- 85 vs. 444.3 +/- 70; POST: 220.5 +/- 59 vs. 259.5 +/- 126 mmol x kg (-1) dw), lactate (PRE: 8.5 +/- 7.7 vs. 8.5 +/- 8.3; POST: 49.9 +/- 19.0 vs. 42.6 +/- 26.6 mmol x kg (-1) dw), phosphocreatine (PRE: 77.9 +/- 11.6 vs. 75.7 +/- 16.9; POST: 65.8 +/- 12.1 vs. 61.2 +/- 12.7 mmol x kg (-1) dw) or pH (PRE: 6.99 +/- 0.12 vs. 6.99 +/- 0.08; POST: 6.86 +/- 0.13 vs. 6.85 +/- 0.06), respectively. There were also no significant differences in blood lactate responses to the two patterns of exercise. These data suggest that, when the average power output is similar, large variations in exercise intensity exert no significant effect on muscle metabolism.
G Brickley; S Green; D G Jenkins; M McEinery; C Wishart; J D Doust; C A Williams
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-10-06
Journal Detail:
Title:  International journal of sports medicine     Volume:  28     ISSN:  0172-4622     ISO Abbreviation:  Int J Sports Med     Publication Date:  2007 Apr 
Date Detail:
Created Date:  2007-04-05     Completed Date:  2007-06-13     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8008349     Medline TA:  Int J Sports Med     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  300-5     Citation Subset:  IM    
Chelsea School Research Centre, University of Brighton, Eastbourne, United Kingdom.
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MeSH Terms
Analysis of Variance
Bicycling / physiology*
Exercise / physiology*
Glycogen / metabolism
Hydrogen-Ion Concentration
Lactates / metabolism
Muscle, Skeletal / metabolism*
Phosphocreatine / metabolism
Reg. No./Substance:
0/Lactates; 67-07-2/Phosphocreatine; 9005-79-2/Glycogen

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

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