I'd say runners load up on carbs to keep their engine running.
Ideally unprocessed or mildly processed whole grains and beans. Something like thick cut rolled oats or grain flakes, some red beans or white beans. Some date paste or honey to hold it together. Spice it up to get anti-oxidants, cinnamon, cocoa. Add in some seeds or nuts, like walnuts, flax, chia, hemp, or sesame seeds. Press them into a bar shape.
I don't have a recipe for them, sorry!
i look for ones with a lot of fiber and low carbs. low fat too. it takes some looking around. are there better nutrition options? sure. but this is packable and storable and something i don't eat every single day.