PHYS-04 · Principle
Do I need to carb-load for a 10 km or a one-hour race?
No. Loading helped only in events longer than about 90 minutes; in shorter races the muscles finish with glycogen to spare, so normal high-carbohydrate eating is enough.
How the body works, agreed across the reviews below; a study entry shows what one experiment measured.
Practical Application
Do I need to carb-load for a 10 km or a one-hour race? No. Loading helped only in events longer than about 90 minutes; in shorter races the muscles finish with glycogen to spare, so normal high-carbohydrate eating is enough.
What it does not mean: that every late fade is the wall (heat, damage and pacing have their own clocks); the 1967 biopsies (REF-452) are this principle's history, not its evidence.
Mechanism
In long hard exercise exhaustion usually coincides with critically low muscle glycogen, which blood glucose cannot fully replace; after 60-90 min of moderate running or cycling plenty is left, so a higher start adds nothing (REF-819).
The pool inside the myofibrils is linked to reduced calcium release in fatigue: where glycogen runs low matters, not only how much (REF-472).
Common misreading
"Carb-load before every race": the store limits only efforts long enough to run it down.