Exogenous Ketosis Impairs 30-min Time-Trial Performance Independent of Bicarbonate Supplementation

In a double-blind crossover study, 14 well-trained male cyclists completed a 30-minute time trial followed by an all-out sprint after receiving 50 g ketone ester, 180 mg/kg sodium bicarbonate, both, or a control drink. Ketone ester raised blood D-beta-hydroxybutyrate to about 3 to 4 mM and lowered blood pH by 0.05 units and bicarbonate by 2.6 mM versus control, and bicarbonate co-ingestion counteracted this acid-base disturbance. Mean power output in the time trial was similar for control and bicarbonate at 281 W, and 1.5 percent lower in the ketone ester conditions. Sprint time to exhaustion was about 64 seconds in control and ketone ester, and about 8 percent longer with bicarbonate.