Mid-run fueling: when carbs start to actually matter

A trained runner stores roughly 90 minutes' worth of glycogen — the carbohydrate fuel your muscles and brain run on at higher intensities. Up to that point, your tank covers the work. After it, the tank starts running dry, and your pace starts paying the bill.

This is why the rule of thumb is straightforward: under 75-90 minutes of running, water is enough. Over 90 minutes, you need carbs on the run. Not because you'll bonk in the next mile if you skip them, but because your stores are finite and the longer you push past empty, the worse your second half gets and the longer your recovery takes.

The targets that consistently show up in the research:

• Runs 75-150 minutes: 30-60 grams of carbohydrate per hour
• Runs over 150 minutes (or marathon pace): 60-90 grams per hour, ideally a glucose-plus-fructose mix to clear faster
• Start by 30-40 minutes in, not when you feel low — by the time you feel the wall, you're an hour behind on fueling

What form does it take? Whatever sits well in your gut. Gels and chews are designed for fast absorption and easy carrying. Sports drinks deliver carbs plus fluid plus electrolytes in one move. Real-food options — dates, energy bars, even gummies — work too, with the caveat that fiber and fat slow absorption and can sit badly on race day.

The piece most intermediate runners miss: the gut is trainable. If you only fuel on race day, your stomach will fight you. Practice mid-run fueling on every long run from about 90 minutes up. By race day, taking on 60 grams an hour should feel boring, not heroic.

A late-run pace fade or a creeping heart rate in the final third of a long run is often blamed on fitness. As often as not, it's fuel.

Source: Laura Norris Running — The Runner's Guide to Fueling for Long Runs