Impact of ketone ester supplementation on exercise performance, training adaptations, and sleep

In the last decade, elevating blood ketone body levels by the intake of ketone esters (KE) has emerged as a popular nutritional strategy among athletes to improve endurance exercise performance. However, despite that a few studies report an ergogenic effect of KE supplementation during high-intensity exercise, the major body of evidence indicates that KE supplementation during exercise under normal conditions with adequate carbohydrate intake does not enhance endurance performance. However, research indicates that consuming KE during exercise in challenging environmental conditions, such as hypoxia and heat, may potentially enhance endurance performance. However, consistent with research in normal conditions, we found no ergogenic effect of KE supplementation during endurance exercise in hypoxia and heat. Nonetheless, under these conditions, KE intake was associated with beneficial physiological effects, such as an increase in blood and muscle oxygenation status in hypoxia, and a reduction in diuresis during exercise in the heat. In the second part of this doctoral research project, the impact of post-exercise ketone ester (PEKS) supplementation on sleep and training adaptations was investigated. In these studies, we showed that post-exercise and pre-sleep KE intake counteracts exercise-induced sleep dysregulations following acute evening exercise, as well as during periods of intensified training. Nevertheless, our results suggest that from a perspective of improving sleep, pre-sleep KE supplementation is only relevant when sleep is disturbed, and it does not improve 'normal' sleep in individuals who already exhibit good sleep quality. Lastly, we demonstrate that PEKS is not only beneficial during overload training, but also improves training adaptations and endurance performance during a well-balanced training program. In addition to the previously reported ability of PEKS to increase circulating EPO and skeletal muscle capillarization, we show that PEKS also enhances mitochondrial adaptations in response to endurance training. In conclusion, building on previous research, our results further indicate that KE supplementation is primarily advantageous post-exercise to improve exercise recovery and adaptation. In contrast, KE supplementation does not appear to be ergogenic during exercise, even under challenging environmental conditions.