A large body of evidence over the last two decades has shown that creatine supplementation improves strength and muscle gains. While the primary function of creatine is to provide more efficient fueling of high-intensity exercise, there remains interest in identifying other beneficial metabolic effects.
One intriguing finding in previous studies was the observation that muscle glycogen was higher in subjects supplemented with creatine. Researchers from the United Kingdom recently studied this phenomenon in greater detail.
They had a group of healthy men perform an exhaustive bout of cycling to decrease muscle glycogen. For 6 days after exercise they consumed a standardized high-carbohydrate diet. During the 6 days of recovery, half the subjects started a creatine-loading regimen consisting of 20 grams of creatine monohydrate per day. The other group of subjects received a placebo. Muscle biopsies to determine creatine and glycogen levels were performed immediately after exercise, and after 1, 3 and 6 days.
As expected there were no changes in muscle creatine content with placebo, but creatine supplementation increased total muscle creatine on day 1, 3 and 6 by a total of 9%, 14% and 24%, respectively. The exercise bout caused a significant depletion of muscle glycogen, that then increased markedly during the first 24 hours of recovery in both groups. The rate of glycogen synthesis during this first day of recovery was an astounding 82% higher in the creatine group. Thereafter, muscle glycogen continued to increase at a similar rate at day 3 and day 6 such that muscle glycogen remained higher in the creatine group.
The researchers performed several other measures to determine how creatine might be augmenting muscle glycogen but were unable to attribute the creatine-induced glycogen enhancement to any known mechanism. These findings confirm in a very well-controlled experiment that creatine supplementation in combination with a high-carbohydrate diet augments muscle glycogen levels. For athletes consuming a high-carbohydrate diet, it seems prudent to incorporate creatine supplementation to not only enhance performance, but also metabolic recovery.