Our EXSS Impact post this week was developed by Eric Trexler, who is a recent graduate program alumnus and currently a PhD student in Human Movement Science at UNC. Many thanks to Eric and his mentor Dr. Abbie Smith-Ryan for contributing this week’s post.
Why did you do this study?
Nutritional supplementation is increasingly common in a wide range of populations ranging from competitive athletes to the general public. Creatine monohydrate is among the most widely used supplements by strength and power athletes, whereas caffeine is one of few supplements thought to improve performance in both strength/power and endurance athletes. A number of popular nutritional supplements have been formulated to include both creatine and caffeine, with the intention of improving high-intensity exercise performance.
Early studies on creatine demonstrated performance improvements while mixing creatine powder into caffeinated tea or coffee, but preliminary evidence has suggested that caffeine supplements (caffeine anhydrous) may negate the performance benefits of creatine supplementation. Coffee is a highly concentrated source of caffeine, but the first study to compare coffee to caffeine powder/capsule supplements suggested that the supplement form improves endurance performance more than an equivalent dose of coffee. This finding has recently been challenged, and has not been tested in the context of strength or sprint performance. This study was designed to help answer these important, unresolved questions about two of the most commonly used nutritional supplements in the multi-billion dollar supplement market.
What did you do and what did you find in this study?
This study consisted of an acute phase and a chronic phase, using a sample of 54 resistance trained males. All participants completed baseline strength and sprint testing, consisting of one rep max and repetitions to fatigue for bench press and leg press, along with a repeated sprint test on a stationary bike. For the acute phase, participants returned and consumed either caffeine anhydrous (300 mg), a caffeine-matched dose of coffee, or a placebo beverage 30 minutes prior to exercise testing. This phase was designed to directly compare how equivalent doses of caffeine anhydrous and coffee affect strength and sprint performance. While neither treatment improved strength performance more than the placebo beverage, both caffeine anhydrous and coffee attenuated fatigue to a similar extent during the sprint test.
For the chronic phase, participants received five days’ worth of supplements. There were four groups, and each received one of the following treatments: 1) a standard five-day creatine loading protocol; 2) creatine with additional caffeine anhydrous (300 mg/day); 3) creatine with a caffeine-matched dose of coffee; 4) a placebo beverage. Creatine did not improve strength or sprint performance compared to the placebo beverage, and performance outcomes were not affected by the addition of caffeine anhydrous or coffee. In addition, this study confirmed previous findings in which approximately 30-40% of individuals report mild gastrointestinal discomfort when consuming high doses of creatine with caffeine anhydrous. Interestingly, this effect was not observed when creatine was consumed with coffee.
How do these findings impact the public?
The findings of this study have important implications for recreational and competitive athletes, and may impact future formulations of multi-ingredient supplements. These results suggest that coffee is a viable alternative to caffeine supplements for improving intermittent, high-intensity exercise bouts, which are common in many popular sports. Further, the results demonstrated that high doses of creatine and caffeine anhydrous may cause mild gastrointestinal discomfort when ingested together. It may be helpful to consider the dose, source, and timing of caffeine intake when loading with creatine, and supplement companies may be prudent to avoid formulations containing high doses of both ingredients. Future research may serve to determine if athletes can implement more optimal timing and dosing strategies to simultaneously obtain performance benefits from both creatine and caffeine supplements.