Intermittent Running and Cognitive Performance after Ketone Ester Ingestion

Purpose Ingestion of exogenous ketones alters the metabolic response to exercise and may improve exercise performance, but it has not been explored in variable-intensity team sport activity, or for effects on cognitive function. Methods On two occasions in a double-blind, randomized crossover design, 11 male team sport athletes performed the Loughborough Intermittent Shuttle Test (part A, 5 x 15-min intermittent running; part B, shuttle run to exhaustion), with a cognitive test battery before and after. A 6.4% carbohydrate-electrolyte solution was consumed before and during exercise either alone (PLA) or with 750 mgkg(-1) of a ketone ester (KE) supplement. Heart rate, RPE, and 15-m sprint times were recorded throughout, and serial venous blood samples were assayed for plasma glucose, lactate, and -hydroxybutyrate. Results KE resulted in plasma -hydroxybutyrate concentrations of similar to 1.5 to 2.6 mM during exercise (P < 0.001). Plasma glucose and lactate concentrations were lower during KE compared with PLA (moderate-to-large effect sizes). Heart rate, RPE, and 15-m sprint times did not differ between trials. Run time to exhaustion was not different (P = 0.126, d = 0.45) between PLA (mean = 268 s, 95% confidence interval [CI] = 199-336 s) and KE (mean = 229 s, 95% CI = 178-280 s). Incorrect responses in a multitasking test increased from pre- to postexercise in PLA (mean = 1.8, 95% CI = -0.6 to 4.1) but not in KE (mean = 0.0, 95% CI = -1.8 to 1.8) (P = 0.017, d = 0.70). Conclusion Compared with carbohydrate alone, coingestion of a KE by team sport athletes attenuated the rise in plasma lactate concentrations but did not improve shuttle run time to exhaustion or 15-m sprint times during intermittent running. An attenuation of the decline in executive function after exhausting exercise suggests a cognitive benefit after KE ingestion.