Routinely, athletes and coaches pursue novel nutritional strategies in an attempt to support exercise training techniques and/or enhance athletic performance. Body carbohydrate (CHO) stores are limited so strategies to enhance fat use and spare CHO during exercise and thus, attenuate the onset of fatigue are commonplace. It has been suggested that oral exogenous ketone administration is ergogenic not only by altering exercise metabolism (sparing CHO), but also by improving exercise cognitive function as well as enhancing post-exercise glycogen resynthesis. However, data supporting these claims are limited and contradictory. Therefore, the purpose of this dissertation was to explore the role of exogenous ketone type, i.e., salts (KS) vs ketone monoester (KME) supplementation on various aspects of performance to provide more insight into the current body of evidence. Study 1 showed that relative to an isoenergetic control, acute ingestion of both a caffeinated KS supplement and the same KS supplement without caffeine improved Wingate peak power output, following a 20 km time trial (TT20km), while only the caffeinated supplement improved the best effort TT20km. Therefore, these performance benefits were likely due to the added caffeine or taurine, not the ketones. Study 2 demonstrated that co-ingestion of KME and CHO after glycogen lowering exercise (GLE) vs isoenergetic CHO alone, resulted in no significant differences in any of the exercise performance parameters suggesting that glycogen resynthesis post exercise was not enhanced with KME. Study 3 revealed that, following induced mental fatigue, KME attenuated the decline in cognitive function during exercise in a complex reaction test, when compared to a non-caloric placebo. Taken together, these data demonstrate that 1) acute KS supplementation is not likely to be ergogenic nor detrimental for intense exercise performance, 2) KME supplementation may improve some aspects of cognitive function during exercise, and 3) KME supplementation has little effect on post-exercise glycogen synthesis following prior GLE. Relative to the ergogenic potential of ketones for athletes, these data are intriguing, but more study is needed to assess fully whether and how ketone supplements are beneficial for athletes
