This study is investigating the effects of oral ketone and sodium bicarbonate administration on physiological and metabolic parameters during cycling endurance exercise in hypoxia. Ketone body supplementation is commonly used among elite endurance athletes that also compete in the hypoxia (at altitude). To-date effects of ketones have only been investigated in normoxia and the data in hypoxia is lacking. Hence, we want to investigate the effect of oral ketone ester intake with and without additional sodium bicarbonate (NaHCO3) ingestion on i) blood-acid base balance and ii) exercise performance during prolonged exercise under hypoxic conditions. Information obtained via this study should provide valuable information with regard to optimisation of exercise training and athletic performance, and more importantly, provide pioneering insight on the metabolic and physiological responses to ketosis under hypoxic conditions.

Inclusion Criteria:

• Males between 18 and 35 years old
• Recreational or competitive cyclist performing regularly cycling training sessions of at least 4 hours, with an average training volume of more than 6 hours per week
• Good health status confirmed by a medical screening
• VO2max higher than 55 ml.min-1.kg-1
• Body Mass Index (BMI) between 18 and 25

Exclusion Criteria:

• Any kind of injury/pathology that is a contra-indication to perform high-intensity 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, including a maximum of one glass of wine per day
• Involvement in elite athletic training at a semi-professional or professional level
• Current participation in another research trial
• Any other argument to believe that the subject is unlikely to successfully complete the full study protocol