Creatine is non-essential, nitrogenous, naturally occurring acid that is produced in the human body from the amino acids glycine and arginine.
The body relies on creatine stores as the dominant substrate to rephosphorylate (resynthesize) energy during brief, explosive exercise lasting <several seconds.
The availability of phosphocreatine (PCr) in the muscle significantly influences the amount (and rate) of energy generated during brief, high-intensity exercise. As we store only around 80-120g in the body (dependent on muscle levels), additional creatine supplementation allows for a sustained and accelerated rate of energy production.
Previous studies have found short-term creatine supplementation (20-25g/d for 4-7d) can increase total content by 15-30% and PCr by 10-40%. Short-term dosing has been found to increase maximal strength and power, as well as sprint performance and work completed during maximum effort sets. Long-term supplementation (5-25g/d for <7 days and 2-25g/d thereafter <21 months) has also been shown to significantly increase maximal strength as well as power and also fat free mass.
Consequently creatine has become one of the most marketable products available and also one of the most scientifically tested. It is also one of the few supplements available that produce reliable results when demonstrating improved performance when evaluated against control measures in laboratory settings.
Research has indicated that neither short- or long- term dosing affect endogenous creatine synthesis, nor does it affect autonomic feedback loops such as blood pressure or renal/liver function. However anecdotally athletes have reported muscle strain, gastrointestinal discomfort, dehydration and cramp. Additionally some evidence may suggest that creatine supplementation may increase symptoms and incidence of lower body anterior compartment syndrome.
There have been a number of additional benefits reported with creatine supplementation. These include:
– Attenuation of age-related muscle loss (sarcopenia)
– Treatment of neuromuscular conditions such as ALS, muscular dystrophy and Duchenne’s and Huntington’s diseases
– Neuroprotective effects on the brain
– Reduced pain associated with arthritis
– Treatment of creatine deficiencies