Re-fueling on the Run

There’s a variety of sports drinks, gels and bars on the market to provide you with a quick carbohydrate hit whilst on the run. All are designed to boost your energy levels and prevent you from resorting to using fat as a major fuel supply during endurance events.

Research suggests that you should consume between 30-60 grams of carbohydrate per hour (depending on your size and exercise intensity) when exercising. It's worth noting that this is the maximum amount that your body can deal with, so consuming more than this will not make you run faster or further!

As it takes at least 30 minutes for the carbohydrate to be absorbed into the bloodstream, it’s important to start consuming it before you start feeling tired.

Drink & Be Merry!

Sports drinks are a great way to replenish spent energy and also re-hydrate your drained body.

Most big city marathons have drinks like Lucozade Sport at regular intervals. However many people find that they can’t tolerate the taste or suffer from stomach cramps after drinking it. It's worth experimenting on training runs first!

You can buy other brands, such as the Science in Sport PSP22, which are easier to stomach. However carrying a couple of litres of liquid around 26.2 miles can be a bit cumbersome!

Get Gelled Up!

A logistically easier option is to carry energy gels, which can be tucked into shorts, belts and pockets etc.

They are essentially concentrated drinks of about 100 calories each, and they come in range of flavours and textures. It's important to take on some water (usually around 200ml) with the gels to help them get absorbed into your bloodstream.

Beans, Bars & Bananas

Some people carry jelly beans, bars and bananas and munch on them whilst running. These can all be good sources of quick-release energy if you eat a little and often. They also need to be consumed with plenty of water to help them be absorbed.

What Else Should You Know?

You ideally need to strike a balance between carbohydrate availability, performance and minimizing digestive distress. Practice is the best way to do this. 10 miles into your marathon is neither the time nor the place to discover that a particular sports drink gives you diarrhea!

A word of warning, if you're training for less than an hour, you should not be using sports gels or drinks. You only need to be taking on water to avoid dehydration.

Finally, the amount of glycogen stored in your muscles before you set off will have a huge impact on your performance. To boost your glycogen levels, you should eat plenty of carbohydrates in the days before, and morning of your marathon. This will mean that you will be able to run for longer and harder before you have to rely too much on your fat stores (see Part 1) for fuel.

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Fueling the Grueling Marathon Miles

You see plenty of weary runners guzzling sports drinks, like Lucazade Sport, on events such as the London Marathon without really knowing what it’s doing to their body and how much they should be knocking back at each mile.

But to understand why and when you should consume sports drinks & gels, it’s first helpful to know a bit about the way your body uses fuel for exercise, and why you get tired on a long run.

Muscle Power

When you start exercising, your main supply of fuel is the glycogen that's stored in your muscles and liver. But this is in limited supply. The harder you work, the faster it’ll run out.

As you tick off the miles during a marathon, your body starts to burn proportionally less glycogen and instead turns to blood sugar and body fat for energy.

Fuel for Thought

However, your brain relies on blood sugar to function properly, and it simply can’t let this supply run out. So as levels drop, your body increasingly switches over to fat as a preferred fuel source.

Unfortunately fat, in comparison to blood sugar and glycogen, takes much longer to be converted into energy. The more your body relies on fat as an energy source, the slower and harder things become.

On top of that, converting fat into fuel requires considerably more oxygen, so you’ll also become increasingly out of breath too!

From relative comfort into pure torture!

After about 2-3 hours, you may develop temporary hypoglycemia. At this point, your body has a depletion of muscle and liver glycogen stores together with low blood sugar levels.

Runners call it “hitting the wall” whilst cyclists refer to it as “bonking”. Symptoms include light-headedness, heavy legs, severe tiredness, and you generally feel like you’re giving a 16 stone man a piggyback!

Read "What’s the Point of Sports Drinks & Gels?: Part 2" to find out how you can make things easier!