Racing 5 min
Hitting the wall: what causes it and how to avoid it
Hitting the wall during a race happens when your muscles run out of glycogen—the stored carbohydrate fuel they rely on for sustained effort. It's a sharp drop in performance that feels like running through treacle, and it's entirely preventable with proper fuelling and pacing.
What happens when you hit the wall
Glycogen depletion causes a sudden loss of power, coordination and mental sharpness. Your legs feel heavy, your pace drops dramatically, and even easy running feels impossibly hard. This typically occurs in races over 90 minutes—marathons, half-marathons, and longer trail runs—when glycogen stores in your liver and muscles become critically low.
Why your glycogen runs out
Your body stores roughly 90 minutes' worth of glycogen at race pace. Once depleted, your muscles must rely on fat oxidation, which produces energy more slowly and feels substantially harder. Running too hard early, skipping carbohydrate loading, or under-fuelling during the race all accelerate glycogen depletion.
How to build and preserve glycogen stores
- Carbohydrate-load 3 days before racing: increase carbs to 8–12g per kilogram of body weight daily
- Time your pre-race meal 2–4 hours before the start to top up liver glycogen
- Sleep well and reduce training volume in the final 48 hours
- Stay hydrated throughout training and the days before racing
Fuel during the race
Consume 30–60g of carbohydrate per hour from about 45 minutes in. This tops up blood glucose and delays glycogen depletion. Use gels, sports drinks, energy bars or real food—whatever your gut tolerates at race pace. In races over 2.5 hours, aim for the higher end of that range.
Pacing matters as much as fuelling
An aggressive early pace burns through glycogen faster, regardless of how much you've eaten. Run the first half of a marathon at or slightly slower than goal pace, spare glycogen for the second half, and you'll avoid the wall entirely. Running a sensible, even-paced race is often more effective than any fuelling strategy.
Training your gut for race-day fuelling
Your digestive system needs practice. Run long training sessions—at least a few beyond 90 minutes—with your planned race fuelling strategy. This trains your gut to absorb carbohydrates efficiently and identifies any products that cause discomfort before race day matters.
Using data to dial in your plan
Tracking your fuelling strategy, pacing and how you felt during long runs creates a personal data set. RunV-style coaching uses this information to refine your race-specific fuelling and pacing targets based on your actual physiology, not generic rules. Record carb intake, race splits, and perceived effort to build a repeatable, evidence-based approach.
Key takeaways
- Carbohydrate-load properly and fuel early in the race
- Run a disciplined, even pace—don't burn glycogen unnecessarily
- Train your gut on long runs to practise your fuelling strategy
- Use your training data to personalise your race-day plan
FAQ
- Can you recover if you hit the wall mid-race?
- Partially. Once severely depleted, glycogen takes 20–30 minutes to restore via carbohydrate intake, during which your pace will stay depressed. Prevention is far more effective than recovery. If you do hit the wall, consume 30–40g of fast carbs, slow your pace to comfortable and wait.
- Is hitting the wall the same as bonking?
- Yes—bonking is just another term for glycogen depletion. Both describe the same sharp loss of performance when carbohydrate fuel runs out.
- How much should I drink during a race?
- Drink to thirst, aiming for 400–800ml per hour depending on heat, humidity and effort. Overhydration increases cramp risk; underhydration impairs performance. The carbohydrates in sports drinks also aid fluid absorption and glycogen management.
Train smarter
RunV turns this thinking into your plan — adaptive coaching that rebuilds after every run.
Keep reading
