Creatine is thought to act as an intramuscular backup to supply the phosphate your body needs to regenerate adenosine triphosphate, or ATP, the immediate source of energy for muscle contraction. ATP produces energy when it gives up a phosphate molecule, becoming adenosine diphosphate, or ADP. If enough creatine is stored in the muscle, the creatine donates its phosphate to regenerate ATP. The body synthesizes an average of one gram a day of creatine from the amino acid precursors glycine, arginine and methionine. You get another gram a day if you eat meat and fish.
Shortly after creatine was introduced to the sports-supplement market, a series of studies found that the most efficient way to take it involved loading 20 grams a day in four five-gram doses for five days. After that a maintenance period followed, in which you took three to five grams. It was all designed to fill muscles with creatine rapidly. Later studies demonstrated that you could also load muscles simply by taking three grams a day for 30 days; however, more recent research shows that you’d need to take five grams a day for the long-term creatine load to work.
Other studies have found that loading creatine for just two days produces a significant ergogenic effect. A recent study of women found that while loading creatine for two days did increase muscle stores, it failed to increase exercise work capacity. The consensus is that muscle creatine peaks after three to six days of loading, although other research shows that after two days of loading, 60 to 70 percent of the dose is excreted.
The latest investigation of creatine loading featured 17 healthy young men randomly assigned to either a creatine or a placebo group. Those in the creatine group took 20 grams a day in five-gram doses four times a day. Both groups lifted weights during the study. The five-day creatine regimen led to a 12 percent increase in anaerobic power, along with an 11 percent increase in one-rep-maximum back-squat strength. The creatine users also experienced an increase in lean mass and a 4 percent drop in bodyfat levels. Taking creatine for only two days didn’t yield those performance gains, although muscle creatine did increase.
It appears that you need to load creatine for five days minimum to get maximum results. Other questions, however, remain unanswered. For example, if the muscles are loaded with creatine after two to three days, why don’t you see exercise improvements until after a five-day load? Also, since we know that after two days of loading creatine you excrete 70 percent of the total dose, what continues to boost exercise power? My guess is that it’s the increased muscle protein synthesis, as well as higher levels of creatine-induced IGF-1. Those would involve reactions that go beyond merely boosting energy stores in muscle.
Law, Y.L., et al. (2009). Effects of two and five days of creatine loading on muscular strength and anerobic power in trained athletes. J Strength Cond Res. 23:906-914.
— Jerry Brainum