Each week, I ask a question about a common running science myth. Answer correctly and you'll be entered into the weekly raffle.
For a typical runner, at what long-run duration does carb fueling during the run start to meaningfully affect next-day recovery and performance?
A. 45 minutes — any aerobic session burns enough glycogen to warrant fuel ⏱️🍯 (21.7%)
B. 60 minutes — anything shorter and you’re fine on water alone ⏰💧 (34.8%)
C. 90 minutes — the classic “bonk line” where glycogen depletion starts to bite 🚫🥖 (28.3%)
D. 2 hours — below that, fat oxidation covers everything you need 🔥⚡ (15.2%)
Why this is right
At easy-to-moderate paces, liver + muscle glycogen is good for roughly 90 minutes before depletion starts compromising performance and recovery. The exact number shifts with pace and fitness — elite marathoners fuel earlier because they burn faster — but 90 minutes is the inflection point where fueling during the run starts paying off.
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