Carbohydrate Timing for Endurance

For endurance performance, when carbohydrate is consumed around training is genuinely impactful because glycogen is limiting (see glycogen).

Before: A carbohydrate-containing meal 1–4 hours pre-exercise tops off liver and muscle glycogen; for events, 1–4 g/kg of carbohydrate in the hours beforehand is typical. For multi-day or repeated events, carbohydrate loading maximizes stores (see carb-loading).

During: Recommendations scale with duration (ACSM/AND/DC):

• 30–60 min: little or no carbohydrate needed (water suffices).
• 1–2.5 h: ~30–60 g/h of carbohydrate.
• >2.5–3 h: up to ~90 g/h, achievable only with multiple transportable carbohydrates (a glucose-to-fructose blend, often ~2:1) that use separate intestinal transporters to exceed the ~60 g/h single-sugar absorption ceiling and reduce GI distress.

After: Begin glycogen restoration promptly when recovery time is short — ~1.0–1.2 g/kg/h of higher-glycemic carbohydrate for the first few hours when there are fewer than ~4 hours before the next session (see recovery-nutrition). With a full day to recover, simply meeting daily carbohydrate targets restores glycogen.

• Pre: carb meal 1–4 h before; ~1–4 g/kg for events.
• During: none <60 min; ~30–60 g/h for 1–2.5 h; up to ~90 g/h beyond, via glucose:fructose (~2:1).
• Single-sugar absorption caps near 60 g/h; mixed sugars raise the ceiling.
• Post: ~1.0–1.2 g/kg/h for first hours if <4 h to next session.
• Timing matters most for endurance; less so for short sessions.

• glycogen — the store this timing manages.
• endurance-fueling — applied fueling for races/long sessions.
• carb-loading — pre-event maximization.
• recovery-nutrition — rapid post-exercise refueling.