Fuelling Activity: Nutrition for the Trails

by Neil Cooper

Anyone who has run a marathon or watched one on television will have heard of the dreaded experience of “hitting the wall.” It's something walkers, runners and cyclists alike all suffer from - but what does the phrase really mean? And if hitting the wall feels this horrible, how can we avoid it?

What is physically happening when we hit the wall?

Carbohydrate is stored in our bodies in the form of glycogen, which is a type of fuel our body can use to keep us going during activity. The problem is that we can only store a maximum of about 90 minutes’ worth before our tank is empty and we’re entirely out of fuel. At this point, the wall has been hit.

We can refuel our body as we carry out our activity, but the amount of fuel our body can absorb during strenuous activity is limited. We can only absorb about 60g of carbohydrates per hour. For cyclists, this can be in the form of energy bars, sports drinks or solid food. Most cyclists use the obligatory cake stop to refuel, but it is also important to refuel frequently during the ride. For runners, taking on solid food can lead to gastro distress, so using liquids in the form of sports drinks or gels (or even the new jellies which are less syrupy and easier to digest) are used more frequently. Unsalted nuts, dried fruit and jelly babies can also be effective, but everyone is different, so see what works for you.

Walkers are less likely to hit the wall due to the fact they tend to use energy less quickly. By using less energy, their heart rate remains lower and therefore they use a different fuel, which is fat. Everyone has sufficient fat to sustain activity for days rather than hours. Fat is used when the activity is less strenuous, which can be gauged by whether you can hold a decent conversation whilst carrying out the activity. Walkers still need to refuel regularly, as some glycogen will be burned but at a far slower rate. Remember as well that your body burns more fuel when it is cold as it tries to keep you warm, so you will need to refuel more in the cold.

Don’t forget to hydrate

Regardless of the type of activity, hydration is vital. Dehydration will not only ruin your day, but is potentially life-threatening too. Make sure you have access to plenty of fluid.

In hot conditions, we know to drink roughly 500ml-750ml an hour to replace the liquid we sweat out. But if you’re on a bike or exercising in cold and windy conditions, you may not realise the amount you are sweating. It’s important you keep that fluid intake up regardless.

Most sports drinks contain minerals which are lost when you sweat, such as sodium and potassium. During strenuous activity, they are the most effective way of hydrating, refuelling and maintaining your correct mineral levels.

Follow these tips and you should avoid hitting the dreaded wall!