Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Kinesiology

Supervisor

Lemon, Peter W.R.

Abstract

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.

Summary for Lay Audience

Carbohydrates (CHO - sugars and starches) are an important fuel for brain and muscle during exercise but unfortunately body stores are limited and reduction of these stores is linked to fatigue. Athletes and coaches often seek procedures that can help support exercise training or improve exercise performance, so strategies to increase fat use and/or spare CHO during exercise are common. Some researchers believe that oral ketone administration can help improve exercise performance not only by sparing exercise CHO use, but also by improving exercise cognitive function (decision making, reaction time, etc.), as well as increasing body CHO stores during recovery following exercise. However, evidence to support the veracity of these claims is both modest and inconsistent. Therefore, the purpose of this dissertation was to explore the role of oral ketone type, i.e., salts (KS) vs ketone monoester (KME) supplementation on different aspects of performance to provide more insight into this research area. Study 1 showed that drinking a caffeinated, KS supplement and the same KS supplement without caffeine improved performance of an intense 30-sec sprint, after a 20 km cycling race (TT20km), while only the caffeinated supplement improved the TT20km. These performance benefits were likely due to the added caffeine or taurine, not the ketones. Study 2 demonstrated that drinking KME and CHO after intense exercise resulted in no differences in exercise performance 4 h later, compared to drinking CHO alone. This implies that refilling of CHO stores after exercise was not better with ketone supplementation. Study 3 showed that, after inducing mental fatigue, KME reduced the deterioration in cognitive function during exercise in a complex reaction test. Taken together, these data demonstrate that 1) KS supplementation likely does not improve nor worsen intense exercise performance, 2) KME supplementation may improve some aspects of cognitive function during exercise, 3) KME supplementation has little effect on refilling CHO stores after exercise. Regarding the ability of ketone supplements to improve performance in athletes, these data are intriguing, but more study is needed to evaluate fully if and how ketone supplements are beneficial for athletes.

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