Journal Title (Medline/Pubmed accepted abbreviation): Eur. J. Appl. Phyiol.
Page numbers: 1669-1677
Summary of background and research design:
Background: Creatine is a popular supplement used for gaining muscle mass. It buffers exercise-induced hydrogen ions (H+) and increases the body’s potential to produce ATP. The increased work that an athlete can perform during an exercise session allows greater gains more quickly.
Caffeine stimulates hormones such as adrenaline (epinephrine) and independently increases performance. However, due to the proposed mechanisms of action and conflicting results from various performance studies, some believe that caffeine may nullify the benefits of creatine.
Hypothesis: Short term creatine supplementation (5 days) would increase anaerobic energy during repeated sprints and, with a single dose of caffeine 1 hr before the sprints, performance would be enhanced further.
Subjects: Twelve physically active men, age 19 ± 0.6 yrs old
Experimental design: randomized, double-blind, cross-over
Treatments: Creatine: 0.3 g/kg body weight (Phosphagen HP™) per day divided into 4 doses per day, consumed with meals.
Caffeine: 6 mg/kg body weight. (420 mg for a 70 kg or 154 lb man; equivalent to about 4 cups of coffee)
Placebo: 6 mg/kg body weight of maltodextrin.
Protocol: The participants arrived at the laboratory not having eaten for the last 4 hrs. At the first visit, they were familiarized with the sprint protocol: 6 x 10 sec sprints on a stationary bicycle with 60 sec in between sprints. They completed a control trial at visit 2 without creatine or caffeine with heart rate monitored and blood samples collected at various time points throughout the test. Mean peak and power were monitored during the cycling tests. The participants consumed creatine for 5 days before both visits 3 and 4. One hr before the sprint test on visit 3 or 4, the participants consumed caffeine and, on the other visit, the placebo. Blood was analyzed for lactate, glucose, epinephrine, and norepinephrine. Visits 3 and 4 were separated by at least 1 month.
Summary of research findings:
- About half of the participants experienced a mild sense of anxiety and/or trembling after the dose of caffeine; one was slightly nauseated. This indicates that this dose of caffeine elicited stimulating effects in a relatively large percentage of subjects.
- In regard to mean and peak power, supplementation with creatine and caffeine augmented performance in at least the first 3 sprints compared to creatine + placebo and the control; there were no significant differences in performance during the last 3 sprints.
- Lactate concentrations in plasma increased with each subsequent sprint for all treatments. The highest lactate and glucose concentrations were seen with the creatine + caffeine treatment. This, in conjunction with the observation that caffeine increased heart rate, suggests that the cardiovascular system was under more stress.
- One hr after caffeine was ingested, norepinephrine concentrations were the lowest measured. However, there was a large variability in epinephrine and norepinephrine plasma concentrations and not other significant differences were seen for either hormone or time point.
Key practice applications:
Caffeine ingestion as a one-time dose did not negate the effects of short-term creatine use on performance during sprints so, if an athlete is not regularly consuming caffeine and is consuming creatine daily, caffeine may further enhance performance.
The relationship between these 2 ergogenic aids appears to be very complex, and it appears that the timing of ingestion of both compounds, the frequency of usage (one-time or chronic), the dose, and other factors probably contribute to whether these 2 supplements work together or work against each other. Importantly, one study was mentioned that reported that caffeine negated the benefits of creatine (Hespel et al., 2002); this study instructed participants to consume caffeine and creatine both for 3-4 days before the exercise test. However, several studies have not reported a negative influence of caffeine on creatine efficacy.
Creatine has repeated shown to increase work volume during exercise. However, more impressively, creatine has also shown many long term benefits such as increased rates of gain in muscle mass, strength, and power. A study that lasts for a longer term, for example 8 wks instead of 5 days, may be able to better tease out the effects of caffeine + creatine.