Testing Sabastian was at the leading edge of performance science. To fully translate his potential into real-world results required going to new depths.

Testing included: 

Stable isotope ¹³C labeling to measure exogenous carbohydrate uptake 

Doubly labeled water to assess energy expenditure 


Running economy and VO2 max testing 


Lactate testing and blood sampling 

Body-composition assessments, including Bioelectrical impedance analysis (BIA), to monitor training adaptations
 

Ongoing training-load monitoring 

Thermoregulation data collection
 

Analysis of detailed food-intake logs to ensure sufficient energy availability

Sabastian has always had a high tolerance to fueling — it has never been a performance limitation. And yet, several months of testing, analyzing, and refining his fueling protocol meant being able to increase his race day carbohydrate target. It was a plan tailored to his body and his goal. 

In spite of his excellent tolerance, alongside the testing, Maurten nutritionists developed a personalized gut-training plan and a race-day fueling protocol to enhance and increase his ability to utilize the carbohydrates he consumed on race day. He took a Maurten Gel before long sessions and Maurten Drink Mix at set intervals during training runs — mimicking his exact race-day schedule. This was aimed at progressively conditioning his gut and instilling good training habits. 

At the Berlin Marathon in 2025, Sabastian had a target of around 105 grams of carbohydrates per hour. In London this increased to 115 grams, with a total race goal of 230 grams — enough to fuel a sub-2 effort.