I know I dont know everything, but from what I have read...
Scientific Investigation into the Rationality of Carbohydrate
Consumption Criterions in Correlation to Post-Training
Anaerobic Depletion Patterns
"Glycogen synthase action is inversely relative to glycogen intensity (23); as a result of the glycogen-depleted state post-training, skeletal muscle (24) and hepatic glycogen synthase activity are raised (13).
Basal glucose transport within skeletal muscle occurs via GLUT-4 (A powerhouse effect of insulin is the stimulation of glucose transport via the translocation of the insulin responsive glucose transporter, GLUT4, to the plasma membrane) (14).
Nevertheless, the ability of skeletal muscle to take up glucose is relative, due to adjustments in the GLUT-4 content of the sarcolemal membrane.
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In the post-workout period, therefore, muscle membrane permeability to glucose is high, thus favoring the accretion of glycogen replacement. However, if rapid carbohydrate distribution is not provided during recovery, glycogen synthesis will be limited because the rate of endogenous glucose production from gluconeogenic precursors such as alanine and glycerol is inadequate to support maximal rates of glycogen synthesis (15).
The ingestion of high GI carbohydrates increases glycogen synthesis in two ways.
The first (12) is increased substrate availability through the increased blood glucose concentration, which results in an increased glucose uptake due to mass action.
Moreover, the resultant increase in systemic insulin concentration stimulates the translocation of GLUT-4 transporters from an intracellular pool to the sarcolemal membrane (7).
The hormone insulin is also a powerful activator of glycogen synthase and inhibitor of glycogen phosphorylase (2).
"The effectiveness of a specific carbohydrate in encouraging resynthesis of the carbohydrate stores is reliant on the insulin and glucose response to the carbohydrate load (4).
This is directly linked to gastric emptying and intestinal absorption rates. It is also associated with the insulinogenic potential of the carbohydrate, as indicated by the glycemic index (GI) of a carbohydrate.
The development of glycogen synthesis relies upon the accessibility of glycogenic substrate (8) and the activity of the enzymes implicated in glycogen synthesis. These include hexokinase and glycogen synthase.
Prior exercise enhances skeletal muscle glucose transport (3) because of the translocation of GLUT-4 transporters from an intracellular pool to the sarcolemal membrane.
The inclination for skeletal muscle to extort blood glucose will thus be increased, and the glucose will tend to be directed toward glycogen synthesis because glycogen synthase is activated during recovery due to the low intramuscular glycogen concentration (23).
These conditions favoring the resynthesis of glycogen can be exploited (8) by the provision of a quality carbohydrate source.
The consequential amplification in glucose availability and the insulin response to the glucose load would tend to stimulate (7) a further increase in the GLUT-4 content of the sarcolemal membrane.
Research has demonstrated (11) that there is a direct correlation between the rate of glycogen storage during recovery and total muscle GLUT-4 protein content
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