How to Avoid Hitting the Wall in a Marathon (London Marathon Strategy)

Running a marathon is as much about brain as it is about brawn. Every runner knows the dread of “hitting the wall” – that moment when legs turn to lead and your mind wants to stop as badly as your muscles. But with the right plan, you can push that wall way past mile 26. For a club runner like me (just a regular UK road racer with a job and mortgage), it’s all about smart fueling, sensible pacing, and listening to your body. Here’s how to stay strong to the finish line.

Understanding Glycogen: Why the Wall Happens

Think of glycogen as your fuel tank of stored sugar, kept in muscles and liver. It’s the body’s prime energy for running. But it’s limited – roughly 300–500 grams in most runners, which translates to about 90–120 minutes of marathon-pace running. In plain terms: if you go hard from the start without refueling, you’ll empty those stores well before 26 miles. Once glycogen is gone, your body switches to burning fat, which can’t keep up at race speed. That’s when the wall hits – your brain fogs, coordination stumbles, and your legs feel impossibly heavy.

Good news: training can boost your tanks. Long runs force your body to adapt, storing more glycogen than someone untrained. But even with perfect training, you can’t pack enough glycogen to run a whole marathon at speed – so race-day fueling is non-negotiable.

What Happens When Glycogen Runs Out

When that sugar tank nears empty, you feel it. You’ll notice fatigue spike, breathing gets heavy, and your legs suddenly feel like they have lead in them. It can feel like tripping over your own feet or forgetting how to breathe efficiently. In short: “bonking” isn’t just feeling tired, it’s a full-on metabolic crisis that hits hard and fast.

Fueling Strategy: Gels, Carbs and Timing

You’ve probably heard the mantra: “Fuel early and often.” It’s true. Your race performance hinges on it. Since stored carbs won’t last, you must refill on the move.

Pre-Race Carb Loading

In the days before race, pile on the carbs. Aim for around 7–12 grams of carbohydrate per kilogram of body weight in the 2–3 days leading up to the marathon. That might sound like a lot, but this “carb-loading” fills your muscles with extra glycogen. In practice, that means a high-carb diet (pasta, rice, potatoes, low-fibre bread, etc.) starting mid-week. Just don’t overdo it at the pasta party – a too-large meal on race morning can leave you feeling bloated. A breakfast rich in easily digestible carbs about 2–3 hours before the start will top off your liver glycogen without upsetting your stomach.

During the Race: Gels, Drinks and More

Once you’re out on course, start fueling before you feel desperate. For most runners, that means taking something ~30–45 minutes after the gun. A common mistake is waiting for “the wall” sensation; by then you’re already behind. Instead, take a gel or sports chew early, then roughly every 30–45 minutes (about 3–4 gels per hour). Each gel typically packs 20–30 grams of carbs, so this gets you through that ~60–90g of carbs per hour that many plans recommend.

Always practice your race fueling plan on long runs. Never try a new gel or drink on race day. We’ve all heard horror stories of gel-induced stomach revolts or “the incident” behind a hedge. If a particular brand of gel or timing worked well on your training runs, stick with it in the race.

Water is important, but fuel is king. Ideally, sip fluids alongside carbs. If you wait until you feel parched, you’re already dehydrated. Many runners carry a few mini gels or sports chews in a jacket pocket or belt so they can grab them anytime they reach a small flat section or an aid station.

Hydration and Electrolytes

Staying hydrated helps you digest fuel and keep pace, but in a hot race you can’t just pound water. In Manchester last year I learned that the hard way: it was boiling, I chugged far too much water, and I ended up feeling sloshy and crampy. Instead, sip small amounts frequently – maybe a few sips of water or sports drink every 15–20 minutes. On warm days, use a sports drink or electrolyte tablets in one bottle. The sodium helps your muscles fire and keeps your fluids balanced. Drinking too much plain water can actually dilute your salt levels, so keep that in mind on hot days.

Pacing: Start Smart, Finish Strong

You’ve heard the crowd yell “GO!” and adrenaline shoots through your legs. It’s tempting to hang on the coattails of faster runners in the first miles. Resist it. Even a few seconds per mile too fast can burn through your glycogen much quicker. Think of pacing as a bank account. Spend too much early, and you’re bankrupt at mile 20. Instead, aim for an even (or slight negative) split: stick to your goal pace (or a touch slower) for the first half, then try to speed up a little if you feel good.

In London, the first few miles include some downhills out of the Mall and through Westminster – use that to relax into your rhythm. The real challenge often comes in the last 10K. Canary Wharf’s tall buildings can act like wind tunnels, and the air by Greenwich can feel muggy. By then, fatigue is creeping in, so those final miles can feel like you’re running up a hill (even if it’s flat). Expect it, and plan to ease back slightly before the last stretch so you have something left for the finish.

On the bright side, London’s crowds can lift you up. When fatigue hits around 20 miles, imagine all those spectators cheering you on and push through with shorter strides or power-walking the very gentle uphills. By mile 25–26, adrenaline and pride take over, and you’ll be amazed how the legs can move even when you swore they wouldn’t.

Key Tips and Takeaways

• Start fuelling early. Take your first gel or carb drink 30–45 minutes in and then roughly every 30–45 minutes after. If you wait until you feel starved, it’s already too late.
• Carb-load in advance. Eat extra carbs (pasta, rice, potatoes) 2–3 days before the race to top off your energy tank.
• Practice your nutrition plan in training. Don’t try a new gel or hydration strategy on race day – what works on training runs will work in the race.
• Keep a sensible pace. Stick to even splits or slightly slower early on. Going out too fast wastes glycogen.
• Hydrate smartly. Sip fluids regularly (e.g., a few sips every 15–20 minutes). In heat, use electrolyte drinks or tablets instead of plain water alone.
• Know the course. In London, expect the final miles past Canary Wharf and Greenwich to be tough – save a bit of energy for that stretch.
• Listen to your body. Small aches or cramps can be warning signs: slow down if needed, and take an extra gel or sip if you feel a wall coming on.

Conclusion

“Hitting the wall” can feel inevitable, but it’s really preventable with good strategy. With consistent training, steady pacing, and disciplined fueling, most runners can avoid bonking. The London Marathon is one of the UK’s biggest races – nearly 50,000 finishers last year – and it’s known for its enthusiastic crowds. Go into it with a plan: run steady, take on carbs early, and keep sipping that electrolyte drink. When it hurts, remember that thousands are hurting too, and the finish line will be worth it. The pain is temporary; the pride of crossing that last few steps is forever. Lace up, trust your training, and run smart – the wall won’t stand a chance.

See you at the finish!