Effect of Ketone Ester Supplementation on Sleep and Recovery in Hypoxia

Inclusion Criteria: 1. Written informed consent must be obtained prior to any experimental procedures 2. Males between 18 and 35 years old 3. Recreational or competitive cyclists performing regular cycling training sessions with an average training volume of more than 6 hours per week 4. Good health status confirmed by a medical screening 5. Body Mass Index (BMI) between 18 and 25 6. Normal sleep pattern as assessed by the Pittsburgh Sleep Quality Index 7. Moderate sleep chronotype (extreme morning and evening chronotypes will be excluded), assessed by the Horne and Östberg questionnaire Exclusion Criteria: 1. Any kind of injury/pathology that is a contra-indication for hypoxic exposure and/or to perform high-intensity exercise, evaluated by a sport medical screening 2. Intake of any medication or nutritional supplement that is known to affect exercise, performance or sleep. Intake will be assessed during recruitment and the sport medical screening. 3. Intake of analgesics, anti-inflammatory agents, or supplementary anti-oxidants, from 2 weeks prior to the start of the study. 4. Recent residence or training under hypoxia; more than 7 days exposure to altitude \> 1500m during the last 3 months preceding the study. 5. Night-shifts or travel across time zones in the month preceding the study 6. Blood donation within 3 months prior to the start of the study 7. Smoking 8. More than 3 alcoholic beverages per day 9. Pre-existing, diagnosed psychiatric conditions or diagnosed anxiety 10. Excessive daytime sleepiness as assessed by the Epworth scale 11. Depression or anxiety as assessed by the Beck Depression Inventory and Beck Anxiety Inventory. Only a score in the range of 'normal ups and downs' (score 1-10) for depression or 'minimal anxiety' (score 0-7) for anxiety are tolerated. 12. History of addiction or excessive caffeine/alcohol consumption assessed by a questionnaire 13. Any other argument to believe that the subject is unlikely to successfully complete the full study protocol