Carbohydrates

ESSENTIALS

Fluid Intake

Flexibility

NUTRITION
Introduction

Carbohydrates
Fats
Proteins

Vitamins & Minerals

LIFESTYLE
Rest & Sleep

Smoking

COMPETITION
Goal Setting

Race Day
Warm Up

  Unfortunately, the body’s stores of carbohydrate (glucose and glycogen) are not that great (600-800 kcal). This is about the same amount of carbohydrate that you should get each day from the food that you eat. If, when running at marathon pace you were only able to use carbohydrates as a source of energy, theses stores would only last for around 70min. When the stores of muscle glycogen are depleted, to ability to perform exercise is severely limited. This is known as hitting the wall. This is where fat plays an important role.

A High Carbohydrate Diet Helps Glycogen Refueling

So one of the greatest problems facing the athlete is achieving adequate glycogen repletion to maintain normal energy reserves. This clearly requires time but it has been shown that, after exercise induced glycogen depletion, a diet high in carbohydrate will actually increase the rate of refueling. The flowing graph shows the difference in muscle glycogen levels with a high carbohydrate diet and a low carbohydrate diet:

The refueling process should start as soon as possible after a training session. Ironically the ability of muscle to replete glycogen is greatest in the first hour following exercise, so rather than wait you should make sure that some carbohydrate is available within an hour of training. This is particularly important when training most days or twice a day. A small energy bar would be good, as they tend to be low in fat and have a good mixture of complex and simple carbohydrates.

What are Simple and Complex Carbohydrates?

Simple carbohydrates are what are commonly known as sugars. These are sweet to the taste and are easily absorbed with little digestion. However the rapid absorption in to the blood rapidly increases the blood sugar levels. Insulin then helps to move the glucose in to the cells were it can get converted in to glycogen. If the increase in blood sugar is too rapid then a lot of insulin is released and the blood sugar levels actually end up falling. Simple carbohydrates are often accompanied with high levels of fat, (e.g. chocolate), and low levels of vitamins and minerals which is why they are considered to be less nutritious than complex carbohydrates.

Complex carbohydrates are natural unrefined sugars. This type of carbohydrate includes foods such as rice and pasta. These take a lot longer for the body to digest so the release of sugar in to the blood is a lot slower, which means that the body doesn’t release high levels of insulin. These carbohydrates also contain high levels of vitamins and minerals as well as low levels of fats, which makes them more nutritious than simple carbohydrates.

What type of carbohydrate ?

The relative merits of one form of carbohydrate over another, and the number and timing of meals, in promoting the repletion of muscle glycogen is still the focus of much research. It appears, however, that complex and simply carbohydrates are equally effective in glycogen repletion. Certainly, both are required in the diet to achieve very high intakes of carbohydrate. But the added benefits of an increased consumption of fibre, vitamins and minerals, with an accompanying decrease in fat intake comes with the choice of complex carbohydrates. Eating large amounts of fat takes up useful calories that would be more energy-effective if devoted to complex carbohydrates.

How much carbohydrate?

Exactly how much carbohydrate a swimmer should eat cannot be determined easily. However, at least 50% of a swimmers diet should consist of complex carbohydrates. It is estimated, that a teenage swimmer who trains for 7 hours a week, should consume approximately 3000 kcal a day. This equates to 375grams of complex carbohydrate each day. We must not forget however if the body does not use the carbohydrates taken in and there is nowhere to store it will convert it to fat and store it that way.