In this episode, we sit down with Cas Fuchs (Assistant Professor at Maastricht University) to break down his latest research on muscle and liver glycogen restoration, carbohydrate timing, and what endurance athletes think is happening after a hard session… versus what the data actually shows.

Cas recently published new work demonstrating that a substantial carbohydrate-rich breakfast after an overnight fast did not fully replenish muscle or liver glycogen within three hours in trained cyclists — a finding that challenges common assumptions in endurance nutrition.

We dive into the physiology behind glycogen recovery, the differences between muscle vs liver glycogen, why the famous “90-minute threshold” matters so much for performance, and what this means for athletes training on back-to-back days — from recreational runners to Tour de France pros.

If you’re preparing for an ultra, long cycling event, or simply want to recover faster and perform better, this episode will change the way you think about fueling.

Topics we cover:

Why 90 minutes is a critical threshold for performance and fueling

What happens when athletes skip carbs after training

Muscle vs liver glycogen: why they recover differently

What elite cycling teams do in tight recovery windows

How much (and which) carbohydrate you actually need for optimal recovery

Practical takeaways for endurance athletes and coaches

Links:

Research from Cas Fuchs

Cas Fuchs Instagram

Instagram van Jeroen van der Mark

👉 Coaching 1-1 for hybrid athletes

👉 YouTube: Lift Heavy Run Fast

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👉 Follow Jeroen van der Mark

👉 Next hybrid Gym in Groningen

👉 Coaching 1-1 for hybrid athletes

👉 YouTube: Lift Heavy Run Fast

We dive into his full preparation: training structure, pacing, nutrition, tendon management, and how he stays strong while pushing his endurance to the limit. Xander continues to hit PRs in the gym while taking on brutal mountain ultras — how is that even possible?

Topics

• Was this the hardest challenge Xander has ever done?
• How he structured his training for a 100 km with massive elevation
• Flat ultras vs. mountain ultras: what’s the difference?
• How to prep for elevation when you live in a flat country
• Managing tendon load, niggles and accumulated fatigue
• How he tapered into race week
• Xander’s full nutrition strategy (carbs, fluids, electrolytes)
• His pacing approach for a 10+ hour effort
• Common mistakes ultra athletes make
• How he recovered physically and mentally

👉 Follow Instagram of Xander

👉 Follow Jeroen van der Mark

👉 Coaching 1-1 for hybrid athletes

👉 YouTube: Lift Heavy Run Fast