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[RC] Ed, Let's discuss this paper - Ridecamp Guest

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J Appl Physiol 99: 707-714, 2005. First published April 14, 2005; 
doi:10.1152/japplphysiol.01261.2004
8750-7587/05 $8.00
This Article    
       

Ingestion of a high-glycemic index meal increases muscle glycogen storage at 
rest but augments its utilization during subsequent exercise

Shiou-Liang Wee,1 Clyde Williams,1 Kostas Tsintzas,2 and Leslie Boobis3 1Sports 
and Exercise Nutrition Research Group, School of Sport and Exercise Sciences, 
Loughborough University, Loughborough; 2Centre for Integrated Systems Biology 
and Medicine, School of Biomedical Sciences, Nottingham University, Nottingham; 
and 3Sunderland Royal Hospital, Sunderland, United Kingdom

Submitted 8 November 2004 ; accepted in final form 12 April 2005



The aim of this study was to compare the effect of preexercise breakfast 
containing high- and low-glycemic index (GI) carbohydrate (CHO) (2.5g CHO/kg 
body mass) on muscle glycogen metabolism. On two occasions, 14 days apart, 
seven trained men ran at 71% maximal oxygen uptake for 30 min on a treadmill. 
Three hours before exercise, in a randomized order, subjects consumed either 
isoenergetic high- (HGI) or low-GI (LGI) CHO breakfasts that provided (per 70 
kg body mass) 3.43 MJ energy, 175 g CHO, 21 g protein, and 4 g fat. The 
incremental areas under the 3-h plasma glucose and serum insulin response 
curves after the HGI meal were 3.9- (P < 0.05) and 1.4-fold greater (P < 
0.001), respectively, than those after the LGI meal. During the 3-h 
postprandial period, muscle glycogen concentration increased by 15% (P < 0.05) 
after the HGI meal but remained unchanged after the LGI meal. Muscle glycogen 
utilization during exercise was greater in the HGI (129.1 ± 16.1 mmol/kg dry 
mass) compared with the LGI (87.9 ± 15.1 mmol/kg dry mass; P < 0.01) trial. 
Although the LGI meal contributed less CHO to muscle glycogen synthesis in the 
3-h postprandial period compared with the HGI meal, a sparing of muscle 
glycogen utilization during subsequent exercise was observed in the LGI trial, 
most likely as a result of better maintained fat oxidation.


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