The key to understanding creatine supplementation is to appreciate that it only helps with certain activities. Muscle cells generate mechanical work from an energy liberating chemical reaction. The reaction breaks down ATP, which is used by the muscle very quickly to provide energy, only 2 to 3 seconds. Once the ATP is gone the work stops, but the body has several ways to convert the ADP back to ATP. One way is with creatine. The function of creatine is to replenish adeonsine triphosphate (ATP), during short bursts of high intensity exercise (Volek, 1997). This is during the first energy system (ATP-PCr). Instead of being out of energy in only 2 to 3 seconds, with creatine the all out work can last around 10 seconds. Creatine is a nitrogenous organic compound obtained in the diet predominately from the ingestion of meat or fish, which contains approximately four to five grams of creatine per kilogram. Creatine is also manufactured internally by the liver and kidneys from a few amino acids. The average intake of creatine from a mixed diet has been estimated to be one gram per day. Creatine is synthesized in the liver and kidney, and released into the blood stream to be actively taken up by the muscle cells via specific transport proteins (Clark, 1997). The highest tissue concentrations of creatine are found in skeletal muscle, and approximately two thirds of total is in the form of phosphocreatine (PCr). Phosphocreatine is present inside the muscle cell three to four times that of ATP, and plays an essential role in the normal energy metabolism of muscle because it acts as a buffer for the ATP concentrations. PCr serves an important metabolic role in the rephosphorylation of ADP regenerating ATP. If increased PCr levels are maintained for an extended period of time, individuals in training may benefit from being able to train at higher intensities, for longer periods of time before fatigue sets in. The rate of PCr utilization declines after 1.28 seconds of muscle contraction, while the rate of glycolysis (second energy system) does not peak until after 3 seconds, but starts around ten seconds.
Functionally, creatine supplementation increases both total work output in a single high intensity exercise bout, and increases the peak performance during a series of repetitive bouts. One week of creatine supplementation enhances muscular performance during repeated sets of bench press and jump squat exercise (Volek et al., 1997). Therefore sports requiring power (explosive movements) and strength would be most beneficial for supplementing creatine. Therefore, the enhancement of performance with creatine supplementation is short duration high intensity intermittent exercise and suggests that, in line with theoretical reasoning, the ergogenic effects of creatine supplementation are restricted mainly to short duration high intensity exercise (Balsom et al., 1993).
It is a disappointment that no research has been done on side effects of creatine supplementation and its relationship to injury. No matter how creatine is supplemented, it is obvious that one of the side effects on athletes supplementing creatine is the unexplained increase in body mass. According to recent research, current thinking is that the increased body weight is a result of increased total body water accompanying the elevated creatine stores in muscle (Volek, 1997). While the mechanism is unclear, it appears to be due to water retention in the muscles, which might cause an increase in intramuscular pressure and contribute to muscle dysfunction. Many football programs have noticed the increase in muscle cramps, pulls, and strains among its players. No research has been done to prove these theories. Programs that have banned or publicly demoted the usage of creatine: Tampa Bay Buccaneers, Cincinnati Bengals, San Diego Chargers, University of Oregon.
Summary by: Andrew Dendas, Oregon State University Assistant Strength and Conditioning Coach - Former HSU Assistant Strength Coach