How to Avoid Bonking in Cycling?

What bonking is and why it happens?

Bonking in cycling is a sudden and severe drop in performance caused by depleted glycogen stores, leaving your body without enough available energy to sustain effort.

It typically feels like:

• Sudden loss of power
• Heavy, unresponsive legs
• Dizziness or lack of focus
• Inability to maintain pace

It’s not just fatigue, it’s a fuel depletion problem. In cycling, bonking often happens gradually, then all at once. And once it hits, recovery mid-ride is limited.

Why cyclists bonk?

Bonking is almost always preventable. It comes down to poor fueling, pacing, or preparation.

Riding too hard early

Starting a ride with excessive intensity increases carbohydrate usage quickly.

This leads to:

• Faster glycogen depletion
• Reduced ability to sustain effort later

Even small surges early in the ride can have a significant impact.

Not eating enough during the ride

The most common cause of bonking is simply under-fueling.

Cyclists often:

• Delay eating
• Rely only on water
• Underestimate how much energy they need

Once glycogen is low, performance drops rapidly.

Poor pre-ride nutrition

Starting a ride without adequate carbohydrate intake puts you at a disadvantage immediately.

Common mistakes:

• Skipping meals
• Low-carb intake before long rides
• Starting rides in a fasted state when intensity is high

Lack of fueling practice

Your body needs to adapt to consuming carbohydrates during exercise.

Without practice:

• Digestion may be inefficient
• You may avoid eating enough
• Energy intake becomes inconsistent

How to pace your ride to avoid bonking?

Pacing is the first layer of protection against energy depletion.

Start controlled

Your early effort should feel comfortable and sustainable.

Focus on:

• Smooth pedaling
• Controlled breathing
• Avoiding early intensity spikes

If it feels too easy early on, you’re pacing correctly.

Avoid surges in effort

Short bursts of high intensity, especially on climbs or into the wind, increase carbohydrate usage.

Instead:

• Keep effort steady
• Let speed vary with terrain
• Stay consistent in how hard you’re working

Ride within your limits

Trying to sustain an effort beyond your fitness level will accelerate fatigue and increase energy demand.

A properly paced ride allows you to:

• Maintain power
• Finish strong or steady

Fueling Strategies to Prevent Bonking

Fueling is the most important factor in avoiding bonking during long rides or runs. Your body relies on a steady supply of carbohydrates to maintain energy levels and performance. Without proper fueling, glycogen stores deplete quickly, leading to fatigue and reduced efficiency. Consistent nutrition helps you stay strong from start to finish and supports overall endurance. For more information, check our guide on cycling nutrition.

Start Fueling Early

Don’t wait until you feel tired or hungry to begin fueling. By the time you notice low energy, your body is already running low on glycogen. Starting early ensures your energy reserves remain topped up throughout the session. Aim to begin fueling within the first 20 to 30 minutes of your ride or run to stay ahead of fatigue.

Eat Regularly, Not Occasionally

Large, infrequent intake can lead to energy spikes and crashes, as well as digestive discomfort. This approach makes it harder for your body to efficiently absorb and use nutrients. Instead, focus on taking in small amounts of fuel at regular intervals. This helps maintain steady blood sugar levels and keeps your energy consistent over time.

Use the Right Types of Fuel

Focus on easily digestible carbohydrates such as energy gels, sports drinks, bars, chews, or simple real foods like bananas. These options provide quick, accessible energy without placing stress on your digestive system. Choosing the right fuel also improves absorption and reduces the risk of stomach issues. Practice your fueling strategy during training to find what works best for your body.

Hydration and electrolytes

Hydration plays a key role in maintaining performance.

What to focus on:

• Drink consistently throughout the ride
• Adjust intake based on conditions
• Include electrolytes in longer or hotter rides

Electrolytes help maintain:

• Fluid balance
• Muscle function
• Energy delivery

Training your body to resist bonking

You can improve your resistance to energy depletion through training.

Long endurance rides

Long rides help your body:

• Store more glycogen
• Improve fat utilization
• Sustain effort for longer

Consistent fueling practice

Use training rides to:

• Test nutrition strategies
• Build tolerance to carbohydrate intake
• Improve consistency

This reduces the risk of issues on race day or key rides.

Recognising early signs of bonking

Early detection can help you respond before performance collapses.

Physical signs

• Gradual drop in power
• Increased perceived effort
• Heavy legs

Mental signs

• Loss of concentration
• Irritability
• Reduced motivation

What to do if you start to bonk?

If energy drops mid-ride:

• Reduce your effort immediately
• Take in quick carbohydrates
• Hydrate
• Give your body time to respond

You may recover partially, but full recovery is unlikely once glycogen is severely depleted.

Common mistakes that lead to bonking

• Starting too hard
• Delaying fueling
• Relying only on water
• Ignoring hydration needs
• Not eating before the ride
• Using untested nutrition

Practical checklist: avoid bonking in cycling

• Eat properly before your ride
• Start at a controlled pace
• Fuel early and consistently
• Use easily digestible carbohydrates
• Stay hydrated throughout
• Include electrolytes when needed
• Practice your fueling strategy

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