Document Detail

High-intensity exercise and muscle glycogen availability in humans.
MedLine Citation:
PMID:  10350228     Owner:  NLM     Status:  MEDLINE    
This study investigated the effects of muscle glycogen availability on performance and selected physiological and metabolic responses during high-intensity intermittent exercise. Seven male subjects completed a regimen of exercise and dietary intake (48 h) to either lower and keep low (LOW-CHO) or lower and then increase (HIGH-CHO) muscle glycogen stores, on two separate occasions at least a week apart. On each occasion the subjects completed a short-term (<10 min) and prolonged (>30 min) intermittent exercise (IEX) protocol, 24 h apart, which consisted of 6-s bouts of high-intensity exercise performed at 30-s intervals on a cycle ergometer. Glycogen concentration (mean +/- SEM) in m. vastus lateralis before both IEx(short) and IEx(long) was significantly lower following LOW-CHO [180 (14), 181 (17) mmol kg (dw)(-1)] compared with HIGH-CHO [397 (35), 540 (25) mmol kg (dw)(-1)]. In both IEx(short) and IEx(long), significantly less work was performed following LOW-CHO compared with HIGH-CHO. In IEx(long), the number of exercise bouts that could be completed at a pre-determined target exercise intensity increased by 265% from 111 (14) following LOW-CHO to 294 (29) following HIGH-CHO (P < 0.05). At the point of fatigue in IEx(long), glycogen concentration was significantly lower with the LOW-CHO compared with HIGH-CHO [58 (25) vs. 181 (46) mmol kg (dw)(-1), respectively]. The plasma concentrations of adrenaline and nor-adrenaline (in IEx(short) and IEx(long)), and FFAand glycerol (in IEx(long)), increased several-fold above resting values with both experimental conditions. Oxygen uptake during the exercise periods in IEx(long), approached 70% of Vo2max. These results suggest that muscle glycogen availability can affect performance during both short-term and more prolonged high-intensity intermittent exercise and that with repeated exercise periods as short as 6 s, there can be a relatively high aerobic contribution.
P D Balsom; G C Gaitanos; K Söderlund; B Ekblom
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Acta physiologica Scandinavica     Volume:  165     ISSN:  0001-6772     ISO Abbreviation:  Acta Physiol. Scand.     Publication Date:  1999 Apr 
Date Detail:
Created Date:  1999-07-16     Completed Date:  1999-07-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370362     Medline TA:  Acta Physiol Scand     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  337-45     Citation Subset:  IM; S    
Department of Physiology and Pharmacology, Karolinska Institute and University College of Physical Education and Sports, Stockholm, Sweden.
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MeSH Terms
Dietary Carbohydrates / administration & dosage
Epinephrine / blood
Exercise / physiology*
Exercise Test
Fatty Acids, Nonesterified / blood
Glycerol / blood
Glycogen / metabolism*
Hypoxanthine / blood
Lactic Acid / blood
Muscle, Skeletal / metabolism*
Norepinephrine / blood
Oxygen Consumption / physiology
Reg. No./Substance:
0/Dietary Carbohydrates; 0/Fatty Acids, Nonesterified; 50-21-5/Lactic Acid; 51-41-2/Norepinephrine; 51-43-4/Epinephrine; 56-81-5/Glycerol; 68-94-0/Hypoxanthine; 9005-79-2/Glycogen

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