DYNAMICS OF GLYCOGEN DURING CARBOHYDRATE LOADING REGIMEN
Price, T. B., Petersen, K. F., Laurent, D., & Shulman, G. I. (1997). Timecourse and mechanism of glycogen supercompensation in man. Medicine and Science in Sports and Exercise, 29(5), Supplement abstract 252.
Changes in muscle metabolism during a standard 7-day carbohydrate (CHO) loading protocol were observed.
Ss (M = 5; F = 7) performed a 1-hr treadmill exercise immediately before starting a 3-day high fat diet (60% fat; 20% CHO; 20% protein). At the end of the third day the treadmill exercise was repeated. At the start of the fourth day a high CHO diet was instituted (90% CHO; 8% protein, 2% fat).
During day 3 (high fat diet) metabolite concentrations were similar to resting levels prior to exercise but during the first three days of the CHO diet, muscle glycogen, glucose-6-phosphate, and inorganic phosphate remained elevated over basal levels. On the final day muscle glycogen levels were 1.6 times greater than before the commencement of the protocol while glucose-6-phosphate had returned to resting levels.
Increased levels of glucose-6-phosphate after muscle glycogen depleting exercise suggests that increased glucose transport/phosphorylation activity plays a major role in muscle glycogen supercompensation.
Since men and women respond differently to CHO loading protocols, the combining of them into one experimental group may obscure more important gender specific response features as well as distort what actually occurred.
Implication. The standard 7-day CHO loading protocol produces stages of supercompensation. It is important that if this is to be employed that it be completed fully. Less than complete compliance with the protocol may not produce desirable effects.
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