Does Carb Timing Matter?

August 22, 2025

Carb Timing Still Matters—Even If Glycogen Doesn’t Show It

Study Snapshot:

Title: Delaying post‑exercise carbohydrate intake impairs next‑day exercise capacity but not muscle glycogen or molecular responses (Acta Physiologica, 2024)

Context: Double‑blind crossover in nine recreationally active men. Participants performed high‑intensity interval exercise (HIIE, 10 × 2 min at ~94 % peak power).

Post-session, they either consumed carbohydrates immediately (2.4 g/kg) or delayed intake by 3 hours (water only). Total carbohydrate intake over 24 hours was identical across conditions. Performance was tested again the next day via the same HIIE protocol. Muscle biopsies tracked glycogen, molecular signaling, and gene expression.

What Did They Find?

Metric	Result
Muscle Glycogen	Recovered similarly in both immediate and delayed groups (all the way to ~24 h).
Molecular Signals	Markers like PGC‑1α, p53, p‑ACC, and p‑P38 MAPK showed the same activation regardless of carbohydrate timing.
Next‑Day Performance	The immediate‑carb group performed ~5 more intervals on the HIIE test and reported ~2 points lower RPE than the delayed group.

Coach’s Take: Why Timing Wins Even When Biomarkers Don’t

Performance ≠ Biomarkers: Muscle glycogen and molecular markers may “look fine,” but actual power output and fatigue resistance tell a different story.
Refuel to Perform: Delaying intake doesn’t wreck muscle recovery— BUT it does blunt next‑day high‑intensity endurance capacity.
System‑Wide Recovery Matters: This isn’t just about glycogen. Early refueling likely supports nervous-system recovery, substrate availability, hormonal balance, and psychological readiness.

Final Word

Even when glycogen and molecular markers look similar, delayed carbohydrate intake still hurts next‑day output. Real performance is more nuanced. Prioritize immediate refueling, especially for athletes racing or training again within 24 hours.