REF-1600 · Hultman et al., 1996 · Journal of Applied Physiology · Paper · PubMed

In 31 men, six days of creatine at 20 g a day raised muscle total creatine by about 20%; 2 g a day kept it there for a further 30 days, while without it the level fell gradually and no longer differed from baseline 30 days after stopping; 3 g a day gave a similar rise more slowly, over 28 days. From the abstract

Main caveat: Written from the abstract: group sizes, allocation, the measurement method and any spread are unknown.
limited, mixed evidenceMeasured on a mixed groupRead from the abstract only

Hultman and colleagues studied how dietary creatine and creatine supplements build up in skeletal muscle and then wash out, and how urinary creatinine excretion changes, in 31 men who took creatine in different amounts over different periods. Six days at 20 g a day raised muscle total creatine by about a fifth. Continuing with 2 g a day for 30 more days kept it there.

Without the 2 g a day the level drifted down, and 30 days after the last dose it no longer differed from the starting value, while urinary creatinine excretion rose over that period. Taking 3 g a day for 28 days gave a similar rise of about 20%, reached more slowly.

The authors conclude that 20 g a day for six days is a quick way to load muscle, that 2 g a day then holds the level, and that over the long term 3 g a day is probably as effective at raising stores as the high dose.

Participants

n = 31 men. Age, training status and the number in each regimen are not given in the abstract.

Protocol

Regimens named in the abstract: 20 g a day for 6 days; then 2 g a day for 30 days, or no further creatine; separately, 3 g a day for 28 days.
Outcomes: muscle total creatine (the measurement method is not stated in the abstract) and urinary creatinine excretion.
No placebo or control group is described.

Key Results

20 g a day for 6 days: muscle total creatine up by about 20%.
Then 2 g a day for 30 days: the raised level was maintained.
Then no creatine: a gradual decline; 30 days after stopping, the level no longer differed from the pre-supplement value. Urinary creatinine excretion rose correspondingly over that period.
3 g a day for 28 days: a similar rise of about 20%, more gradual.
The abstract gives no measures of spread, no P values and no group sizes.

Practical Application

This study gives no reason to cycle creatine, and it shows what a break does: in 31 men, muscle creatine rose about 20% on 20 g a day for six days, stayed up for 30 more days on 2 g a day, and no longer differed from baseline 30 days after stopping; 3 g a day reached a similar level over 28 days. It measured muscle stores for about two months, not performance and not years of use.
Loading or not: a low daily dose gave a similar rise over about four weeks, a load in six days; both routes appear in the base, 3-5 g a day or a loading phase then maintenance (REF-060, SYNTH-67), and the ISSN stand found no safety problem up to 30 g a day for five years in the studies it reviewed (REF-352).
Inference, not tested here: because the fall after stopping is gradual and takes about a month, a break of a week or two leaves stores partly raised, and a break simply means reloading afterwards.
Inference, not tested here: the abstract shows no sign of uptake fading during 30 days of maintenance; whether anything changes over months to years is not answered here, and the base holds no trial that compares cycling with continuous use.
Not from this paper; the base's practice and other entries: expect some water-weight gain, and avoid creatine when power-to-weight or weight loss is the priority (SYNTH-67, REF-060); women start from lower stores (REF-530), and this study was in men.

Limitations

Written from the abstract: group sizes, allocation, the measurement method and any spread are unknown.
No placebo or control group is described.
Men only; training status not given.
No performance outcome.
About two months of observation; long-term continuous use was not studied.
Published in 1996.
How this entry was checked and changed
Why this level

an uncontrolled pre-post design, which is B; lowered because the abstract gives no group sizes, no allocation method, no spread and no numbers for the fall after stopping. Muscle creatine content is the subject of the entry, so it is not treated as a marker (rule 3)