Do you drink coffee? If so, you might lose the benefits of creatine loading. A recent double-blind study confirms creatine's efficacy as a bodybuilding supplement, but gives a strong caveat to coffee drinkers.
Nine active men (ages 20-23) took eight doses of 5 grams of glucose placebo, creatine monohydrate or creatine plus caffeine in successive six-day treatments. Caffeine was given after breakfast as a 400-mg capsule. The three treatments were presented in random order separated by three-week washout periods. Subjects were fed standardized diets during the study and the four days before it. After the test subjects had loaded up on creatine for six days, their muscles became enriched with extra phosphocreatine, an effect that wasn't diminished by co-administration of caffeine. Predictably, the glucose placebo didn't increase muscle phosphocreatine levels.
At the beginning and end of each six-day treatment, knee extensor strength was tested using a dynamometer. Maximal isometric strength wasn’t significantly improved by creatine, supporting some previous studies that suggest no benefit of creatine for brief, maximal exertions but contradicting other studies that suggest just such a benefit. When test subjects performed intermittent sets of 10, 20 or 30 leg extensions, creatine loading increased performance (dynamic torque) 10%-23%, while the placebo had no effect. This confirms previous research showing performance-enhancing effects of creatine loading on intermittent, bodybuilding-type exercise.
Creatine's ergogenic benefit was increasingly blunted from set to set when subjects took too little rest (20-60 seconds) between sets. The ergogenic effect returned when a longer rest interval (two minutes) was allowed; it takes time for creatine to he recharged with phosphate (creatine is only half recharged after one minute).
Although creatine alone clearly improved quadriceps performance, the combination of creatine plus caffeine wasn't significantly better than a placebo. Apparently, caffeine neutralized the ergogenic benefits of creatine without blocking the rise in muscle phosphocreatine levels. The effect wasn't due to any performance-lowering effect of caffeine; the last caffeine dose was given 20 hours before the dynamometer testing and caffeine isn't believed to reduce performance.
These study results suggest that anyone wanting the full benefit of a creatine-loading regimen is wise to avoid coffee and other concentrated sources of caffeine. The dose of caffeine used in the study, 400 mg, is about the amount contained in 32 cups of drip or brewed coffee or six cups of instant coffee. Drinking more than two cups of brewed coffee a day is likely to reduce the benefits of creatine loading. More moderate consumption of low-caffeine beverages such as tea or cola is apparently permissible; a tea solution (about 30 mg of caffeine) used in early creatine studies showed good results.