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Why Runners Bonk: How to Avoid Hitting the Wall

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It happens to most distance runners at some point. You’ve been running, or cycling, hard, pushing yourself to your limits, when suddenly things take a sharp turn for the worse. Your body feels like it is moving through treacle. Each leg weighs two tonnes. You might even start to hallucinate. Quickly, and very unpleasantly, everything seems to be shutting down. Congratulations. You’ve just hit the wall.

A quick science lesson: when you run, you burn fat and glucose. The human body has an almost limitless supply of fat cells – even those super-lean and lithe athlete bodies. But glucose – which the body breaks down from carbohydrates – is different. Your muscles rip through these supplies fairly quickly, generally “running out” after around an hour and a half or two.

This is why marathoners and long-distance cyclists “carb load” before a big race – to make sure that storage is at capacity – and why they then often take mid-race carbohydrate supplements, in solid, liquid or gel form.

So what happens if you don’t? Well, for some people, the system just collapses. Either your muscle glucose plummets, leaving your brain yelling at your legs to move, and your legs whimpering that they are made of jelly. Or your blood glucose tanks, and your brain becomes a foggy mess. This is the wall. In cycling, the same effect is called bonking, which ironically sounds more “Carry On” film than “give up now”.

You might still get over that finish line, somehow, but it’s not going to be pleasant.

Bonking FAQ

Do other sports get it?

The dreaded wall can happen to any endurance athlete: running, triathlons or long-distance cycling can all involve long, extended steady efforts. Other sports follow different patterns – a football match may last 90 minutes or more, but the players are likely to be covering ground in short, sharp sprints with rests in between, and with opportunities for refuelling drinks, so glycogen depletion is less likely.

How do I avoid hitting the wall?

Good training, good nutrition and good sleep can all help stave off that crash. Prevention is far more effective than cure. If you start feeling faint, light-headed or jelly-legged, the chances are you’ve left it too late. Most athletes will, therefore, follow a strict schedule when racing, taking their carbohydrate gels or drinks at specific times that work for them, in order to keep that glycogen topped up at a decent level.

RECOMMENDED: How to Train for a Marathon

What kind of carbs should I take?

This comes down to personal choice. Some people can’t chew “solid” tablets or jellies while running, or stomach the taste of gels. Others swear by jelly beans or home-made chia seed gels. For most, it’s a question of experimentation – not just with what works for your energy shot, but also what your stomach can tolerate.

Isn’t it all in the head?

Yes and no. While your brain can’t out-think glycogen depletion, it can help you to cope with it – and one study in the British Journal Of Sports Medicine has showed that thinking too much about the wall can actually “bring it on” quicker. So a positive attitude can only help.

Five steps to surviving the wall

The golden rules to follow if you want to run through it

1. Get some carbs on board, as soon as possible

This is not a time to worry about your sugar intake: get that sports drink or gel down you. You may have blown the PB attempt, but those carbs kick in after 10 or 15 minutes so they can still help you get to the finish.

2. Don’t forget water

Dehydration slows the removal of food from your gut into your bloodstream = hello, wall. Don’t go overboard – many races report more issues from people who have overhydrated than underhydated – but take frequent small amounts.

RECOMMENDED: The Best Running Water Bottles

3. Play mind games with yourself

Legs are starting to “go” but your brain is functioning OK? Give it something else to occupy it. Doing maths problems is surprisingly effective – not least because the lack of oxygen to your brain seems to mean adding two and two will take you about a mile.

4. Look up

In the last few miles of any race your form starts to go. Cyclists start to weave, runners hunch. Try to look up, and “run tall”. Look around you, find some distractions. If negative thoughts are winning, try counting in your head. If it’s good enough for Paula Radcliffe…

5. Break it down

The last thing you need to be thinking about right now is the bigger picture. A useful running cliché is “run the mile you are in”. Just get to the end of that one, then the next, then the next. One step at a time, one leg in front of the other. Just keep moving. Sometimes that’s all you can do.

NEXT: Real-Life Tales of the Bonk