Will carb loading boost your running results?

What is carbohydrate loading?

Carbohydrate stores are an essential fuel source during intense or lengthy runs such as a long distance workout or race. However, the amount of carbohydrate the body can store is limited.

Some runners may be familiar with the term "hitting the wall", which describes the overwhelming fatigue experienced when carbohydrate stores are depleted during a marathon. Carbohydrate loading is a dietary strategy that is used to maximise the amount of stored carbohydrate in the muscles (stored glucose, also known as muscle glycogen). It involves eating a diet high in carbohydrates, and reducing your training load in the days before a race or lengthy training session, allowing you to run faster for longer before fatiguing.

The history of carbohydrate loading

The evolution of carbohydrate loading over the past few decades is an interesting journey in nutritional science.

A low carbohydrate diet depleted muscle glycogen stores (over 3 – 4 days), yet the body super-compensated with increased glycogen stores if a high carbohydrate diet was followed immediately afterwards (also over 3-4 days). Later, a modified version of carbohydrate loading was developed which achieved similar results by eliminating the 3-4 day low carbohydrate glycogen stripping phase.

More recently, research has shown that a high carbohydrate diet can still trigger a super-compensation of glycogen storage within 36-48 hours, and not the 72 hour period as previously thought. 

Practical tips on carbohydrate loading

The following tips offer a guide on how you can incorporate carbohydrate loading into your pre-race routine.

• Choose your event – Carbohydrate loading is best suited to events such as a marathon where your performance may otherwise be impaired by glycogen depletion. There is some evidence to suggest that carbohydrate loading can enhance overall performance in events over a 25 – 30 kilometers distance, however participants in a half-marathon (just over 12 kilometers) may not notice much of an improvement.

• Eat more carbohydrates 1-2 days before your event – In the final day or two leading up to an event such as a marathon, follow a high carbohydrate diet, which can be defined as 10 grams of carbohydrate per kilogram of body weight.

• Choose quality carbohydrates – There are large variations in nutritional quality when it comes to carbohydrate foods such as bread, pasta, rice and breakfast cereals. The less processed, whole grain varieties tend to have a higher concentration of nutrients, and are a better sources of fuel for your body. Starchy vegetables (pumpkin, sweet potato and corn) and fruits are also a good source of carbohydrate and nutrients.

• Don't cut out carbohydrates - It is no longer considered beneficial to undertake a depletion phase prior to carbohydrate loading. It is also important to stress that low carbohydrate diets are designed for weight loss, and are not relevant to well trained athletes, or long distance runners

• Don't carbohydrate overload – Don't eat excessive amounts poor quality carbohydrates at the expense of vegetables, or foods rich in lean protein (fish and seafood, lean red meat, skinless chicken, low fat dairy foods or tofu). These foods provide important nutrients for runners. It’s also important to consciously cut back your carbohydrate intake when you’re less active to prevent weight gain.

• Drink plenty of water – Making sure your body is well hydrated before a marathon or long distance event is a must. The fact that carbohydrates are stored with water in your muscles is another reason to keep your fluids up

• Taper time – Rest is an important part of the process to allow your body to super-compensate its stores of glycogen. Try to limit your physical activity to nothing more than a light stretch in the last few days before your event.