The aim of this study is to investigate the effect of oral ketone administration during and immediately after an ultramarathon. Potential changes in cognitive function (reaction time, number of errors), running performance, jump height, skeletal muscle inflammatory infiltration and hormonal alterations will be the main focus. In this context, subjects (n=24) will perform a 100km ultrarunning trail, while receiving either ketone ester (KE, n =12) or placebo (CON, n=12). Experimental measurements will be performed immediately before and after the ultramarathon as well as 24h after the ultramarathon.

Inclusion Criteria:

• Males between 18 and 55 years old
• Recreational or competitive runner having performed an ultramarathon (>42km) during the last 2 years
• Good health status confirmed by a medical screening
• Body Mass Index (BMI) between 18 and 25

Exclusion Criteria:

• Any kind of injury/pathology that is a contra-indication to perform ultra-endurance exercise
• Intake of any medication or nutritional supplement that is known to affect exercise performance
• Intake of analgesics, anti-inflammatory agents, or supplementary anti-oxidants, from 2 weeks prior to the start of the study.
• Blood donation within 3 months prior to the start of the study
• Smoking
• More than 3 alcoholic beverages per day
• Current participation in another research trial
• Any other argument to believe that the subject is unlikely to successfully complete the full study protocol
• Adherence to a high-fat, low-carbohydrate ketogenic diet (less than 20% of energy intake derived from carbohydrates)