No additive effect of creatine, caffeine, and sodium bicarbonate on intense exercise performance in endurance-trained individuals

Background: Athletes commonly use creatine, caffeine, and sodium bicarbonate for performance enhancement. While their isolated effects are well-described, less is known about their potential additive effects. Methods: Following a baseline trial, we randomized 12 endurance-trained males (age: 25 ± 5 years, VO_2max: 56.7 ± 4.6 mL kg⁻¹ min⁻¹; mean ± SD) and 11 females (age: 25 ± 3 years, VO_2max: 50.2 ± 3.4 mL kg⁻¹ min⁻¹) to 5 days of creatine monohydrate (0.3 g kg⁻¹ per day) or placebo loading, followed by a daily maintenance dose (0.04 g kg⁻¹) throughout the study. After the loading period, subjects completed four trials in randomized order where they ingested caffeine (3 mg kg⁻¹), sodium bicarbonate (0.3 g kg⁻¹), placebo, or both caffeine and sodium bicarbonate before a maximal voluntary contraction (MVC), 15-s sprint, and 6-min time trial. Results: Compared to placebo, mean power output during 15-s sprint was higher following loading with creatine than placebo (+34 W, 95% CI: 10 to 58, p = 0.008), but with no additional effect of caffeine (+10 W, 95% CI: −7 to 24, p = 0.156) or sodium bicarbonate (+5 W, 95% CI: −4 to 13, p = 0.397). Mean power output during 6-min time trial was higher with caffeine (+12 W, 95% CI: 5 to 18, p = 0.001) and caffeine + sodium bicarbonate (+8 W, 95% CI: 0 to 15, p = 0.038), whereas sodium bicarbonate (–1 W, 95% CI: −7 to 6, p = 0.851) and creatine (–6 W, 95% CI: −15 to 4, p = 0.250) had no effects. Conclusion: While creatine and caffeine can enhance sprint- and time trial performance, respectively, these effects do not seem additive. Therefore, supplementing with either creatine or caffeine appears sufficient to enhance sprint or short intense exercise performance.