Why Most Athletes Bonk — And How to Prevent It

What Is Bonking?

Bonking — or "hitting the wall" — occurs when your glycogen stores are depleted and your body can no longer maintain the intensity of exercise. It's a sudden, dramatic loss of energy that can turn a promising race into a survival march.

The Physiology

Your muscles store approximately 400-500g of glycogen, enough for roughly 90-120 minutes of moderate-to-high intensity exercise. Once depleted:

• Blood glucose drops sharply
• The brain signals fatigue
• Muscle contractions weaken
• Pace drops 20-40%

Why Athletes Get It Wrong

Most athletes bonk for three predictable reasons:

Starting too fast — burning glycogen at an unsustainable rate

Fueling too late — waiting until they feel tired to eat

Under-dosing — consuming 20-30g/hr when they need 60-90g/hr

The Prevention Protocol

Before the race:

• Carb-load properly for 48 hours
• Eat a high-carb breakfast 3 hours prior

During the race:

• Begin fueling at 20-30 minutes
• Use dual-transport carbs (glucose + fructose)
• Set a timer to remind yourself to fuel every 20 minutes

Training your gut:

• Practice race nutrition in training runs
• Gradually increase carb intake over weeks

Prevention is always better than cure. Train your fueling strategy as seriously as you train your legs.