Carbohydrates for Performance

Following training & competition, an athlete's glycogen stores are depleted. In order to replenish them the athlete needs to consider the speed at which carbohydrate is converted into blood glucose and transported to the muscles. The rapid replenishment of glycogen stores is important for the track athlete who has a number of races in a meeting. The rise in blood glucose levels is indicated by a food's Glycaemic Index (GI) and the faster and higher the blood glucose rises the higher the GI. 

Studies have shown that consuming high GI carbohydrates (approximately 1grm per kg body) within 2 hours after exercise speeds up the replenishment of glycogen stores and therefore speeds up recovery time. There are times when it is beneficial to consume lower GI carbohydrates that are absorbed slowly over a longer period of time (2-4 hours before exercise). Eating 5-6 meals or snacks a day, will help maximise glycogen stores and energy levels, minimise fat storage and stabilise blood glucose and insulin levels.  

Eating and Competition 

What you eat on a day-to-day basis is extremely important for training. Your diet will affect how fast and how well you progress, and how soon you reach competitive standard. The page on Nutritional Tips provides some general nutritional advice to help you manage your weight and body fat. Once you are ready to compete, you will have a new concern: your competition diet. Is it important? What should you eat before your competition? When is the best time to eat? How much should you eat? Should you be eating during the event? In addition, what can you eat between heats or matches? A lot of research has been done in this area, and it is clear that certain dietary approaches can enhance competition performance.  

What do I need to do? 

Calculate your daily basic and extra requirements, monitor your daily intake (especially your carbohydrates) and then adjust your diet to meet your daily requirements. A good balanced diet should provide you with the required nutrients but does needs to be monitored. The simplest way to monitor the 'energy balance' is to keep a regular check of your weight.

What types of carbohydrates are there?

There are two types of carbohydrates - starchy (complex) carbohydrates and simple sugars. The simple sugar's are found in confectionery, muesli bars, cakes and biscuits, cereals, puddings, soft drinks and juices and jam and honey but they also contain fat. Starchy carbohydrates are found in potatoes, rice, bread, wholegrain cereals, semi skimmed milk, yoghurt, fruit, vegetables, beans and pulses. Both types effectively replace muscle glycogen. The starchy carbohydrates are the ones that have all the vitamins and minerals in them as well as protein. They are also low in fat as long as you do not slap on loads of butter and fatty sauces. The starchy foods are much more bulky so there can be a problem in actually eating that amount of food so supplementing with simple sugar alternatives is necessary.

Your digestive system converts the carbohydrates in food into glucose, a form of sugar carried in the blood and transported to cells for energy. The glucose, in turn, is broken down into carbon dioxide and water. Any glucose not used by the cells is converted into glycogen - another form of carbohydrate that is stored in the muscles and liver. However, the body's glycogen capacity is limited to about 350 grams; once this maximum has been reached, any excess glucose is quickly converted into fat. Base your main meal with the bulk on your plate filled with carbohydrates and small amounts of protein such as meat, poultry and fish. The extra protein & vitamins you may require will be in the starchy carbohydrates.

Lactose Intolerance 

Lactose intolerance results when the mucosal cells of the small intestine fail to produce lactase that is essential for the digestion of lactose. Symptoms include diarrhea, bloating, and abdominal cramps following consumption of milk or dairy products.

Nutrition

For every physical activity, the body requires energy and the amount depends on the duration and type of activity. Energy is measured in kcal and is obtained from the body stores or the food we eat. Glycogen is the main source of fuel used by the muscles to enable you to undertake both aerobic and anaerobic exercise. If you train with low glycogen stores, you will feel constantly tired, training performance will be lower and you will be more prone to injury and illness.

A calorie (cal) is the amount of heat energy required to raise the temperature of 1g of water 1°C from 14° to 15°C. A kilocalorie (kcal) is the amount of heat required to raise the temperature of 1000g of water 1°C.

Nutrient Balance 

Carefully planned nutrition must provide an energy balance and a nutrient balance. The nutrients are:

Proteins - essential to growth and repair of muscle and other body tissues
Fats - one source of energy and important in relation to fat soluble vitamins
Carbohydrates - our main source of energy
Minerals - those inorganic elements occurring in the body and which are critical to its normal functions
Vitamins - water and fat soluble vitamins play important roles in many chemical processes in the body
Water - essential to normal body function - as a vehicle for carrying other nutrients and because 60% of the human body is water
Roughage - the fibrous indigestible portion of our diet essential to health of the digestive system

What are the daily energy requirements?

Personal energy requirement = basic energy requirements + extra energy requirements

Basic energy requirements (BER) 

For every Kg of body weight 1.3 kcal is required every hour. (An athlete weighing 50Kg would require 1.3 × 24hrs × 50Kg = 1560 kcal/day) For a more accurate calculation, see the calculator on the Resting Daily Energy Expenditure (RDEE).

Extra energy requirements (EER)

For each hours training you require an additional 8.5 kcal for each Kg of body weight. (For a two hour training session our 50Kg athlete would require 8.5 × 2hrs × 50Kg = 850 kcal) An athlete weighing 50Kg who trains for two hours would require an intake of approx. 2410 kcal (BER + EER = 1560 + 850)

Energy Fuel

Like fuel for a car, the energy we need has to be blended. The blend that we require is as follows:

57% Carbohydrates (sugar, sweets, bread, cakes) 30% Fats (dairy products, oil) 13% Protein (eggs, milk, meat, poultry, fish)

The energy yield per gram is as follows: Carbohydrate - 4 kcal, Fats - 9 kcal and Protein - 4 kcal. (Note: 1 calorie = 1 Kcal)

What does a 50 kg athlete require in terms of carbohydrates, fats and protein? Carbohydrates - 57% of 2410 = 1374 kcal - at 4 kcal per gram = 1374 ÷ 4=343 grams Fats - 30% of 2410 = 723 kcal - at 9 kcal per gram = 723 ÷ 9 = 80 grams Protein - 13% of 2410 = 313 kcal - at 4 kcal per gram = 313 ÷ 4=78 grams

Our 50kg athlete requires 343 grams of Carbohydrates, 80 grams of Fat and 78 grams of Protein