Why Early Carb Intake is Key to Ultra Marathon Performance

Why Start Fuelling Early (Within 1-2 Hours)

1. Preserving Glycogen Stores
   • Your body has limited glycogen stores, and by consuming 60-90g of carbs per hour from the start, you help preserve those stores for later in the race when fatigue sets in and intensity might increase. Waiting until the 4-hour mark could result in faster glycogen depletion, making it harder to catch up later.
2. Optimal Carb Absorption
   • The body’s ability to absorb and process carbohydrates is a gradual process. By starting early, you ensure a consistent supply of energy, which helps prevent energy dips and delays the onset of fatigue.
3. Sustained Energy
   • Even in the early stages, the body is working hard, and keeping a steady intake of carbs helps maintain energy levels, particularly during the crucial first few hours when pacing and efficiency are key.

Why Not Wait Until 4 Hours

• If you delay fuelling until the 4-hour mark, you risk starting to deplete glycogen stores too quickly in the first hours, leading to energy crashes or a "bonk" later in the race.
• Starting fuelling later may also increase the risk of GI distress, as your body will suddenly need to handle a larger carb load after already running for hours.

Recommended Strategy

• First 1-2 Hours: Aim to consume 60-90g of carbs per hour from the start of the race. This could come from a combination of gels, liquid nutrition, and easily digestible solids.

• After 3-4 Hours: Maintain a similar intake (60-90g/hour), adjusting based on how you feel. It’s essential to continue fuelling consistently throughout the race rather than playing catch-up later.

By starting early, you help avoid energy depletion and ensure that your fuelling strategy is balanced across the entire race.