What creatine is
Creatine is a naturally occurring compound made from three amino acids — arginine, glycine and methionine. Your body synthesises it in the liver, kidneys and pancreas, and approximately 95% of your body's creatine is stored in skeletal muscle in the form of phosphocreatine.
It is also found in food, primarily in meat and fish. A 100g serving of raw beef contains roughly 400mg of creatine. Vegetarians and vegans have lower baseline muscle creatine stores because they consume no dietary creatine, which is one reason they often see the largest performance improvements from supplementation.
How creatine works
During high-intensity exercise — sprinting, heavy lifting, explosive movements — your muscles use ATP (adenosine triphosphate) as their primary energy currency. ATP is depleted rapidly, typically within 8–10 seconds of maximal effort.
Phosphocreatine stored in muscle acts as a rapid reservoir for regenerating ATP. It donates a phosphate group to ADP (adenosine diphosphate) to recreate ATP, extending the duration of high-intensity output before fatigue sets in. Supplementing with creatine increases the phosphocreatine stored in muscle, directly expanding this energy buffer.
What creatine does in practice
More phosphocreatine means more ATP can be regenerated quickly during short, intense efforts. This translates to more reps at a given weight, faster sprint times, and reduced fatigue during high-intensity repeated efforts.
Over time, the ability to train at higher volumes produces greater muscular adaptation. This is why creatine's muscle-building effect is indirect — it works by improving training quality and recovery, not by directly stimulating muscle protein synthesis.
Who benefits most from creatine
People who perform resistance training, sprint-based sports, or any activity requiring repeated high-intensity bursts benefit most. Creatine's mechanism is specific to the phosphocreatine energy system, so it is most relevant for activities lasting under about 30 seconds of maximal effort.
Vegetarians and vegans tend to see larger improvements than meat-eaters because their baseline muscle creatine is lower, giving more room to increase stores with supplementation.
Endurance athletes doing pure steady-state work see less benefit, since the phosphocreatine system is not the primary energy source for low-intensity sustained activity. However, creatine still supports high-intensity efforts within endurance training sessions.
Creatine and the brain
Creatine is not only stored in muscle — the brain also contains phosphocreatine and relies on it for rapid ATP regeneration during demanding cognitive tasks. Emerging research suggests creatine supplementation may support cognitive performance, particularly during sleep deprivation or mental fatigue.
This area of research is less mature than the athletic performance evidence but is growing. For now, cognitive benefits are a plausible secondary effect rather than a primary reason to supplement.