Eat and pace yourself properly to avoid the dreaded ‘bonk’, or hitting the wall. Say goodbye to energy slumps…

Steer clear of energy slumps

At this time of year we triathletes like to start pushing ourselves that little bit harder and further in training. This has one unfortunate consequence: the sight of troubled looking age-groupers slumped over coffee and cake at roadside cafes, as they succumb to the dreaded ‘bonk’.

Bonking isn’t as much fun as it sounds, in triathlon or cycling terms (runners more often call it ‘hitting the wall’). It describes the moment when you suddenly run out of fuel to ride or run, resulting in immediate loss of power and an overwhelming desire to stop. This is usually accompanied by a crippling drop in morale, only solved by consumption of sugar.

Your body can store around 2,000 calories in glycogen, stored in your muscles and your liver. This carbohydrate source is your most readily available fuel during hard exercise, and the one your body will choose to use first when your heart rate is up. However, if you start increasing the length of your rides or runs then you might run out of glycogen; typically you’ll only store enough for 90 minutes to two hours of intense exercise. The harder you’re training, the quicker you’ll bonk. Once that glycogen store is used up, your body will switch to burning fat, which means you won’t be able to keep up your pace.

There are a few ways to prevent this from happening. Firstly and most simply, you just need to eat and drink more. You should aim to take on 60-90g of carbohydrates every hour during long sessions – that’s a couple of gels or a litre of energy drink. You can also train your body to become more efficient at using fat as a fuel, which means you’ll have a virtually limitless supply of energy during races. This takes months and a great deal of patience, as you’ll need to train at a lower heart rate and wait for your speed to catch up. Finally, you can pace yourself better when you’re out training. Bonking is a common problem when you’re training with friends, as inevitably you become competitive, start chasing each other to higher speeds – and probably forget to eat and drink while you’re at it. If you do end up hitting the wall, stop (you’ll want to), and find some sweets or sugary drinks to get you home.

Make it work: three ways to avoid hitting the wall

1. Do long, slow training. Teaching your body to use fat as a fuel means using fat as a fuel during training. To do this you need to keep your intensity really low, certainly at a pace where you can talk easily.

2. Train with fuel. Some people avoid taking on food as it upsets their stomach, but this inevitably leads to bonking, so train your gut to cooperate by gradually introducing energy drinks and gels into steady training sessions.

3. On race day, stay steady. You’re most likely to become emotional or forgetful and stop eating, and go too fast, during a race. Use an object measure such as power output or heart rate to control your speed.

Liz Hufton

Team Talk: Starting Out

“Carry some emergency Coke on long rides – the caffeine will help your mood recover” Liz Hufton, Editor

Check out the rest of our nutrition section as well as checking out our top triathlon training plans