Carbohydrate Loading for Endurance Sports

Carbohydrate Loading in preparation for the Dublin Marathon


Darren Macfarlane Sports Injury Clinic, Galway.

What is a Carbohydrate?

Carbohydrate is the body’s prime fuel source when it is physically active. Carbohydrates are a group of complex compounds consisting of carbon, hydrogen and oxygen and include both sugars and starches. When carbohydrate is broken down in the body it is stored as glycogen in the liver and the muscles. Glycogen is the most readily available and efficient source of energy used in any vigorous activity such as running. Inadequate glycogen may limit performance in endurance events lasting more than 90 minutes. Depletion of muscles glycogen is associated with the onset of fatigue. The athlete must then use fat as the primary source of energy with a subsequent reduction in the level of intensity of exercise (you will slow down during race)

'Carbohydrate loading' is probably one of the most misunderstood terms in sports nutrition. People commonly think anyone involved in sport needs to 'carb up' and the way to do this is to eat 'flat out' in the days leading up to an event. Read on to get the facts on carbohydrate loading.

What is carbohydrate loading?

Carbohydrate loading is a strategy involving changes to training and nutrition that can maximize muscle glycogen (carbohydrate) stores prior to endurance competition.

It has been used to since the 1960s as a nutritional strategy to enhance endurance performance lasting more than 90 minutes. Today’s modern day loading has changed since then due to ongoing research and is now more manageable for athletes. Today, 1-4 days of exercise taper while following a high carbohydrate diet (7-12g/kg body weight) is sufficient to elevate muscle glycogen levels. The aim is to boost glycogen stores by optimizing the use of carbohydrate as a fuel source. This is seen to extend endurance by increasing the ability of the body to use carbohydrate as a fuel source.

Does carbohydrate loading improve performance?

With carbohydrate loading it is possible to increase glycogen stores by 20 per cent above normal .This extra supply of carbohydrate has been demonstrated to improve endurance exercise by allowing athletes to exercise at their optimal pace for a longer time. It is estimated that carbohydrate loading can improve performance over a set distance by 2-3%.

Who should carbohydrate load?

Anyone exercising continuously at a moderate to high intensity for 90 minutes or longer is likely to benefit from carbohydrate loading. Typically, sports such as cycling, marathon running, longer distance triathlon will benefit from carbohydrate loading. Shorter-term exercise is unlikely to benefit as the body's usual carbohydrate stores are adequate. Carbohydrate loading is generally not practical to achieve in team sports where games are played every 3-4 days.







What does a high carbohydrate diet look like?

The following diet is suitable for a 70kg athlete aiming to carbohydrate load:

Breakfast 3 cups of low-fibre breakfast cereal with 11/2 cups of reduced fat milk


1 medium banana


250ml orange juice


Snack toasted muffin with honey


500ml sports drink


Lunch 2 sandwiches (4 slices of bread) with filling as desired


200g tub of low-fat fruit yoghurt


375ml can of soft drink


Snack banana smoothie made with low-fat milk, banana and honey


cereal bar


Dinner 1 cup of pasta sauce with 2 cups of cooked pasta


3 slices of garlic bread


2 glasses of cordial


Late Snack toasted muffin and jam


500ml sports drink

This sample plan provides ~ 14,800 kJ, 630 g carbohydrate, 125 g protein and 60 g fat.


What are the common mistakes made when carbohydrate loading?

Research indicates that many athletes who attempt to carbohydrate load, fail to achieve their goal. Common mistakes include:

• Carbohydrate loading requires an exercise taper. Athletes can find it difficult to back off training for 1-4 days before competition. Failing to rest will compromise carbohydrate loading. If you train hard right up to competitions this will deplete glycogen stores and it will be pointless in carbohydrate loading.

• Many athletes fail to eat enough carbohydrate. It seems athletes don't have a good understanding of the amount of food required to carbohydrate load. Working with a sports dietitian or using a carbohydrate counter can be useful.

• In order to consume the necessary amount of carbohydrate, it is necessary to cut back on fibre and make use of compact sources of carbohydrate such as sugar, cordial, soft drink, sports drink, jam, honey, jelly and tinned fruit. Athletes who include too many high fibre foods in their carbohydrate loading menu may suffer stomach upset or find the food too bulky to consume.

• Carbohydrate loading will most likely cause body mass to increase by approximately 2kg. This extra weight is due to extra muscle glycogen and water. For some, a fear of weight gain may prevent them from carbohydrate loading adequately.

• Athletes commonly use carbohydrate loading as an excuse to eat everything and anything in sight. Consuming too many high fat foods will make it difficult to consume sufficient carbohydrate & may result in gain of body fat. Stick to high-carbohydrate; low-fat foods while carbohydrate loading.

A word of caution: always experiment with any new nutritional or training technique in training before trying it in competition.

Good luck with the Marathon Running, don’t forget to have a post-race Sports Massage to relieve those aching muscles. If you have any pre-race niggles don’t ignore them, give our Galway Clinic a call on 086 1957378

http://www.sportsinjurytherapy.ie/