Bicarbonate Unlocks the Ergogenic Action of Ketone Monoester Intake in Endurance Exercise

PURPOSE: We recently reported that oral ketone ester (KE) intake before and during the initial 30 min of a 3 h 15 min simulated cycling race (RACE) transiently decreased blood pH and bicarbonate without affecting maximal performance in the final quarter of the event. We hypothesized that acid–base disturbances due to KE overrules the ergogenic potential of exogenous ketosis in endurance exercise. METHODS: Nine well-trained male cyclists participated in a similar RACE consisting of 3 h submaximal intermittent cycling (IMT(180′)) followed by a 15-min time trial (TT(15′)) preceding an all-out sprint at 175% of lactate threshold (SPRINT). In a randomized crossover design, participants received (i) 65 g KE, (ii) 300 mg·kg(−1) body weight NaHCO(3) (BIC), (iii) KE + BIC, or (iv) a control drink (CON), together with consistent 60 g·h(−1) carbohydrate intake. RESULTS: KE ingestion transiently elevated blood D-ß-hydroxybutyrate to ~2–3 mM during the initial 2 h of RACE (P < 0.001 vs CON). In KE, blood pH concomitantly dropped from 7.43 to 7.36 whereas bicarbonate decreased from 25.5 to 20.5 mM (both P < 0.001 vs CON). Additional BIC resulted in 0.5 to 0.8 mM higher blood D-ß-hydroxybutyrate during the first half of IMT(180′) (P < 0.05 vs KE) and increased blood bicarbonate to 31.1 ± 1.8 mM and blood pH to 7.51 ± 0.03 by the end of IMT(180′) (P < 0.001 vs KE). Mean power output during TT(15′) was similar between KE, BIC, and CON at ~255 W but was 5% higher in KE + BIC (P = 0.02 vs CON). Time to exhaustion in the sprint was similar between all conditions at ~60 s (P = 0.88). Gastrointestinal symptoms were similar between groups. DISCUSSION: The coingestion of oral bicarbonate and KE enhances high-intensity performance at the end of an endurance exercise event without causing gastrointestinal distress.