The Science of Fueling Multi-Day Ultras | Barkley & Cocodona Strategy (Singletrack Clips)

In this clip, Finn Melanson speaks with sports scientist Emily Arrell about one of the most complex problems in ultrarunning: how to fuel multi-day races.

As events like Cocodona 250, the Barkley Marathons, and the Spine Race gain prominence, athletes are pushing far beyond the traditional 100-mile format. That shift raises new questions about carbohydrate intake, hydration, caffeine strategy, real food, sleep deprivation, and how the body actually functions after 40–60 hours on the move.

Emily explains the foundational principles that still matter most - carbohydrates, fluids, and sodium - while also exploring how fueling strategies change as race duration stretches into multiple days.

Topics discussed include:

• Why fueling for multi-day races differs from UTMB or Western States
• How carbohydrate targets change as intensity drops
• Why real food becomes more important in multi-day events
• The role of caffeine when fighting sleep deprivation
• What happens to the gut after 40+ hours of racing
• GI distress and why it still happens at lower intensities
• Sodium and hydration strategies in extreme events
• Whether protein and creatine play a role in multi-day ultras
• The biggest fueling mistakes athletes make in cold races like Barkley

We also discuss the gaps in current research and what scientists still don’t understand about fueling events that last several days.

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