Eight weeks of creatine supplementation, but not creatine plus sodium bicarbonate, increases exercise performance

BACKGROUND: Previous studies have shown that creatine and sodium bicarbonate supplementation independently increase exercise performance. However, it remains unclear if combining these two supplements has an added benefit on exercise performance. The aim of this study was to compare the effects of 8 weeks of creatine alone versus combined creatine plus sodium bicarbonate supplementation on exercise performance. METHODS: Sixty-three healthy, habitually active, adults (28 men, 35 women; 22 +/- 2 years; BMI=23 +/- 3 kg/m(2); VO(2)peak=41.4 +/- 7.6 mL/kg/min) were randomly assigned by sex to one of three supplement groups: placebo (P), creatine only (Cr; 3 g/day), or creatine plus sodium bicarbonate (CrSb; 3 g creatine plus 1 g sodium bicarbonate) for 8 weeks. Exercise performance was measured during repeated sprint tests (6x 10 second sprints) and 5-km time trial, in a counterbalanced order, before randomization and after 8 weeks of supplementation. RESULTS: In the repeated sprints test, peak power output slope significantly differed across the three groups, with significant declines in P (-83%; P=0.04) and CrSb (-82%; P=0.04) but not Cr (35%; P=0.03). In exploratory analyses, mean power output slope significantly decreased in P (-73%; P<0.01) and CrSb (-150%; P <=.0.01), but not in Cr (-8%; P=0.43). In the 5-km time-trial, Cr significantly improved time to completion (-3%; P=0.01), while P (-0.4%; P=0.8) and CrSb (+0.5%; P=0.8) had no significant change. CONCLUSIONS: Eight weeks of creatine supplementation alone increased exercise performance. However, adding sodium bicarbonate supplementation provides no added benefits and may counteract the positive effects of creatine on exercise performance.