Document Detail

The influence of dietary carbohydrate and pre-exercise glucose consumption on supramaximal intermittent exercise performance.
MedLine Citation:
PMID:  8000815     Owner:  NLM     Status:  MEDLINE    
The present study examined whether a pre-exercise consumption of glucose by subjects having adhered to a 3-day low carbohydrate (CHO) or normal CHO diet would influence supramaximal intermittent exercise performance. Sixteen moderately active men volunteers (mean(s.d.) age 20.0(1.3) years) agreed to undertake three exercise tests over an 8-day period; in addition to completing a VO2max test, the subjects performed two identical maximal interval tests (MIT1 and MIT2). Periods of 3 days separated each of the three tests. The interval tests involved five 60-s 'all-out' cycling bouts working against a resistance of 0.075 kg kg-1 body mass; each bout was separated by 5 min of passive recovery. For 3 days preceding the first interval test (MIT1), all subjects adhered to a 'moderate' CHO diet which comprised 59.1% (approximately 4.1 g kg-1 body mass) of the daily energy intake as CHO. Following MIT1 and for 3 days before MIT2 subjects were randomly assigned to follow either a moderate CHO diet (60.8%) or a low CHO diet (14.4% or 1.1 g kg-1 body mass). All food and drink consumed during the experimental period was weighed and recorded for later dietary analysis. One hour before MIT2, eight subjects were administered (in single blind fashion) a 15% glucose solution (1 g kg-1 body mass) while the other eight subjects consumed a low-energy sweetened placebo. During both interval tests, values of work, exercise VO2, plasma glucose, plasma lactate and venous blood pH were statistically analysed. No changes in performance between MIT1 and MIT2 across conditions were found (P > 0.05). However, those subjects who consumed the glucose solution before MIT2 (irrespective of their dietary CHO intake) consumed significantly less oxygen during exercise than those who had been given the placebo solution (P<0.05). While these findings question the ergogenic potential of consuming glucose before supramaximal exercise, the VO(2) data implicate a possible shift in substrate utilization during repeated sprint exercise after pre-exercise glucose ingestion.
D G Jenkins; C A Hutchins; D Spillman
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  British journal of sports medicine     Volume:  28     ISSN:  0306-3674     ISO Abbreviation:  Br J Sports Med     Publication Date:  1994 Sep 
Date Detail:
Created Date:  1995-01-23     Completed Date:  1995-01-23     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0432520     Medline TA:  Br J Sports Med     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  171-6     Citation Subset:  IM; S    
Department of Human Movement Studies, University of Queensland, Australia.
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MeSH Terms
Bicycling / physiology
Blood Glucose / analysis
Dietary Carbohydrates / administration & dosage*,  metabolism,  pharmacology*
Energy Intake
Exercise Tolerance / physiology
Glucose / administration & dosage*,  metabolism,  pharmacology*
Hydrogen-Ion Concentration
Lactates / blood
Muscle, Skeletal / metabolism
Oxygen Consumption / physiology
Physical Exertion / physiology*
Psychomotor Performance / physiology
Single-Blind Method
Work / physiology
Reg. No./Substance:
0/Blood Glucose; 0/Dietary Carbohydrates; 0/Lactates; 0/Placebos; 50-99-7/Glucose

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