Creatine

Creatine is a naturally occurring compound stored primarily in skeletal muscle, where it serves as a rapid energy reserve by regenerating ATP during short, high-intensity efforts. Supplementing with creatine increases intramuscular creatine and phosphocreatine stores by 20 to 40%, which extends the capacity for repeated high-intensity work. A position stand published by the International Society of Sports Nutrition reviewed over 25 years of research and concluded that creatine monohydrate is the most effective legal supplement for increasing high-intensity exercise capacity and lean body mass. It is one of the most extensively researched sports supplements in history.

The direct performance benefit of creatine is strongest for high-intensity, short-duration efforts rather than steady-state endurance work. However, endurance athletes benefit indirectly. Creatine supports higher-quality interval training sessions, faster recovery between hard efforts, and increased muscle glycogen storage. Research published in Medicine and Science in Sports and Exercise found that creatine supplementation improved repeated sprint performance and power output in trained athletes, which translates to better training quality for the interval sessions that build endurance capacity. Creatine also has emerging evidence for neuroprotective effects and improved cognitive function under fatigue.

The standard evidence-based protocol is a loading phase of 20 grams per day, split into four 5-gram doses, for five to seven days, followed by a maintenance dose of 3 to 5 grams per day. Alternatively, skipping the loading phase and taking 3 to 5 grams daily will achieve full muscle saturation in approximately four weeks. The International Society of Sports Nutrition position stand confirms that both approaches produce equivalent long-term results, with the loading phase simply reaching saturation faster. Body mass influences the optimal maintenance dose; larger athletes may benefit from 5 grams daily while smaller athletes are well served by 3 grams.

Creatine supplementation typically produces an initial weight increase of 1 to 2 kilograms during the first week, driven by water retention within muscle cells. This intracellular water retention is a normal physiological response to increased intramuscular creatine concentration and is not fat gain. Over longer periods, creatine supports lean mass gains through improved training quality. For endurance athletes concerned about racing weight, the modest water weight is a consideration, though the performance benefits during training may outweigh the small weight increase during competition. The water retention stabilizes after the loading phase and typically remains steady during maintenance dosing.

Creatine monohydrate has an extensive safety record. A position stand published by the International Society of Sports Nutrition reviewed evidence from studies lasting up to five years and concluded that creatine monohydrate at recommended doses does not cause kidney damage, liver damage, or any other clinically significant adverse effect in healthy individuals. The persistent myth about kidney damage originated from early case reports involving patients with pre-existing renal disease. For individuals with healthy kidneys, long-term creatine use at 3 to 5 grams per day is considered safe by every major sports nutrition and medical body that has reviewed the evidence.