For Students
Muscle fiber types and nutrition
Not all muscle fibers burn fuel the same way — and that has real implications for how different athletes should eat.
Slow-twitch (Type I)
Fatigue-resistant fibers that rely heavily on oxygen and fat oxidation for fuel, well-suited to prolonged, lower-intensity effort like distance running.
Fast-twitch (Type II)
Fibers built for short, powerful efforts that rely heavily on stored glycogen and produce force quickly, but fatigue faster — used in sprinting and heavy lifting.
This split helps explain why endurance athletes (more reliant on sustained aerobic, fat- and glycogen-fueled effort) often need very high carbohydrate intakes to keep glycogen topped up,[1] while strength and power athletes (more reliant on fast-twitch, glycogen-dependent bursts) tend to prioritize protein for muscle repair alongside adequate — but not necessarily extreme — carbohydrate intake. See our full breakdown in macros for endurance vs. strength athletes.