Creatine

Creatine is a compound that helps rebuild ATP during short, high-intensity work.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 258.} About 98% of the body’s creatine is in skeletal muscle, much of it as creatine phosphate; as those phosphate stores run down, the ability to sustain intense work falls.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 258.} Meat is the main food source, and cooking breaks some creatine down.^{2Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 156.}

Supplementing raises muscle creatine by about 20%, up to a ceiling beyond which more has no effect.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 259.} The NSCA textbook describes it as safe and relatively inexpensive, with increases in maximal strength, power and lean mass in trained and untrained people.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 259.} It works better as a training aid than as a one-off performance boost.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 260.}

In practice

• Expect body mass to rise by about 0.5 to 2 kg over weeks to months, partly from extra water in muscle.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 260.}
• The NSCA textbook reports no significant side effects in controlled studies and no reported kidney problems with use for up to five years, though loading can cause occasional mild stomach upset.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 260.}
• The IPTA textbook advises against creatine for people with kidney disease or at risk of it; it can raise blood creatinine and mimic kidney disease on tests.^{5International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 544.}
• Recommending supplements is outside a personal trainer’s scope of practice; trainers can share the evidence and refer clients to a registered dietitian.^{6Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 134.}

Where sources differ

NSCA describes loading at 20 to 25 g a day for five days, then 2 g a day; skipping loading reaches the same muscle levels in about 30 days rather than five.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 259.} The International Personal Trainer Academy gives 0.3 g/kg a day for 5 to 7 days, then 3 to 5 g a day.^{5International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 544.} Helms and colleagues use about 0.04 g/kg (3 to 5 g) a day and consider loading unnecessary for long-term results.^{2Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 156.}