A Ketone Monoester with Carbohydrate Improves Cognitive Measures Postexercise, but Not Performance in Trained Females

Purpose: Acute ingestion of a ketone monoester with co-ingestion of a carbohydrate (KME + CHO) compared to carbohydrate (CHO) was investigated on cycling performance and cognitive performance in trained females. Methods: Using a two condition, placebo-controlled, double-blinded and crossover design, twelve trained females (mean +/- SD: age, 23 +/- 3 y; height, 1.64 +/- 0.08 m; mass, 65.2 +/- 12.7 kg) completed a baseline assessment of cognitive performance (psychomotor vigilance testing (PVT), task switching, and incongruent flanker), followed by 6x5-min intervals at 40%, 45%, 50%, 55%, 60%, and 65% of their maximal power output (W-max) and then a 10-km time trial (TT), concluding with the same assessments of cognitive performance. Participants consumed either 375 mg center dot kg(-1) body mass of KME with a 6% CHO solution (1 g center dot min(-1) of exercise) or CHO alone, across 3 boluses (50:25:25). Results: Blood beta-hydroxybutyrate concentrations averaged 1.80 +/- 0.07 mM and 0.13 +/- 0.01 mM during exercise in KME + CHO and CHO, respectively. Blood glucose decreased following drink 1 of KME + CHO (similar to 15%; P = 0.01) but not CHO, and lactate concentrations were lower in KME + CHO at 50%, 55%, 60%, and 65%W-max (all P < 0.05), compared to CHO. Despite these changes, no differences were found between conditions for TT finishing times (KME + CHO, 29.7 +/- 5.7 min; CHO, 29.6 +/- 5.7 min; P = 0.92). However, only KME + CHO resulted in increases in PVT speed (similar to 4%; P = 0.01), and faster reaction times (similar to 14%; P < 0.01), speed (similar to 15%; P < 0.01), and correct responses (similar to 13%; P = 0.03) in the incongruent flanker during post-testing compared to CHO. Conclusions: Acute ingestion of a KME + CHO elevated blood beta-hydroxybutyrate and lowered glucose and lactate across multiple timepoints during exercise compared to CHO. Although these changes did not affect physical performance, several markers of cognitive performance were improved by the addition of a KME in trained females.