This series of articles concentrates on Taekwondo, but is applicable to any martial art...

Now that you know why carbohydrates are important, this section will be more specific as to do’s and don’ts. It will answer questions on how much carbohydrates to consume, what carbohydrates are preferable, when to eat and some thoughts on carbo-loading.  How Much? To help improve your endurance, delay exhaustion and help you exercise longer and harder you should ensure your pre-exercise glycogen stores are high.

For example, taking a male athlete who weighs 70kg and trains an hour a day:
Body weight = 70 kg
Carbohydrate need = 6g/kg of body weight
Daily carbohydrate need = 70 x 6 = 420 g

Which carbohydrates are preferable?

Traditionally carbohydrates were classified as simple (sugars) and complex (starches and fibres).  Simple carbohydrates consist of one and two sugar units and include glucose (dextrose), fructose (fruit sugar), lactose (milk sugar) and sucrose (table sugar). Complex carbohydrates consist of between 10- and thousand-sugar units (mostly glucose). These include starches, amylase and amylopectin, and non-starch polysaccharides (dietary fibre), such as cellulose, pectin and hemicellulose.

In between simple and complex carbohydrates are glucose polymers and maltodextrin, which consists of between 3- and 10-sugar units. These are popular ingredients in sports drinks and meal-replacement products.

Food usually comprise of a mixture of simple and complex carbohydrates. This makes the traditional classification of simple and complex problematic. A further problem is that it is not necessarily true that simple carbohydrates are digested and absorbed into the bloodstream more rapidly than complex carbohydrates. Apples which are mostly simple carbohydrates produce a small and prolonged rise in blood sugar. On the other hand bread and potatoes which are complex carbohydrates are digested very quickly and give a rapid rise in blood sugar

The Glycaemic Index (GI) have become a more preferred way to describe the effect of foods on blood sugar levels. Foods are ranked from 0 to 100 based on their immediate effect on blood sugar levels. This measurement describes how quickly foods get digested and converted into glucose. The faster the rise the higher the GI-rating.

High or low GI?

Basically if you want efficient glycogen refuelling you need to maintain steady blood glucose and insulin levels. When glucose levels are high (such as after consuming high GI foods) large amounts of insulin are produced which shunts the excess glucose into fat cells. Rapid rise in blood glucose can also result in hypoglycaemia. Conversely low GI foods results in sustained blood glucose levels.

The key is to make sure that your greatest carbohydrate intake is from low GI foods. It is good to know the GI of different foods, and many current books give detailed charts. However there is no need to cut out healthy high GI-foods (such as potatoes). The trick is to merely ensure that the food is not as rapidly digested, by including protein or a little bit of healthy fat. Combining your carbohydrate intake with protein (and healthy fat) results in steadier insulin levels and less fat storage.

When to eat?

A physically active person should have three meals a day of which breakfast is the most important. Make breakfast, especially, and lunch your main meals. For best health benefits keep to the advice of breakfasting like a king, lunching like a prince and dining like a pauper.

Before exercise

For training it is ideal to eat between 2 and 4 hours before training. The meal should typically be high in carbohydrates and low in fat. About 2.5g carbohydrate/kg of body weight 3 hours before exercise. Weighing 70 kg, for example, translates to 175 g carbohydrate.

You shouldn’t feel too full when you begin your training. This will make you feel heavy and sluggish. Especially in the martial arts you need to feel light on your feet. On the other hand you shouldn’t feel hungry and feeble. If you feel weak before the training session top-up with some fluids. Fluids are usually more easily digested, giving you energy quickly, but without you feeling heavy. Pre-workout snacks such as shakes, smoothies, fresh fruit, energy bars or diluted fruit juices should not be used directly before training. Give yourself at least an hour free of food to ensure feeling light and avoid discomforts such as heartburn.

Experiment with the quantity of food or drink and the timing that works best for you.

During exercise

For a training session that lasts less than an hour you needn’t drink anything but water. If the session continue over an hour consuming carbohydrate during the workout can be beneficial. It may help you delay fatigue, enable you to perform at a higher intensity and help you to continue longer even after muscle glycogen stores are depleted. During the first hour of exercise most of your energy comes from muscle glycogen.

An intake of around 30-60 g carbohydrate/hour during exercise is recommended. Taking in any more will not have significant effects as your muscles can only take in a certain amount from your blood stream during aerobic exercise. It is important to take in fuel before fatigue sets in.  Remember that it takes a while (about 30 minutes) for the carbohydrates to be digested and taken into the blood stream.

Moderate to high GI-carbohydrates are better during exercise as you need a rise in blood sugar more rapidly. Carbohydrate in liquid form (i.e. sports drinks or diluted fruit juice) is more convenient, because it provides fluid as well as fuel.

Consuming carbohydrate during training may delay fatigue, but it will not allow you to keep exercising indefinitely. (Fatigue is not only caused by an insufficient supply of carbohydrate, but other factors play a role as well.)

After exercise

The more depleted your glycogen stores, the longer it will take you to refuel your muscle glycogen levels. Obviously the higher the intensity and the longer the duration of the session was the more depleted your glycogen stores will be. Taekwondo’s explosive techniques (plyometric training such as fast or jumping kicks) should be considered high intensity. It can take from 20 hours to 7 days to refill muscle glycogen.

Plyometric training can cause muscle fibre damage. The same is true of excessive stretching exercises. This muscle damage delays glycogen replenishment even further and can take as long as 7-10 days for complete glycogen replenishment to take place. (Proper resting between heavy training sessions seems logical.)

The higher your daily carbohydrate intake the faster you can refuel. Insufficient carbohydrate intake will result in sooner fatigue during exercise and smaller training gains.

Post-exercise replenishing should start as soon as possible. Glycogen storage happens faster directly after exercise. This post-exercise ‘window’ is during the first 2 hours where replenishing happens at about one-and-a-half times the normal rate. During the subsequent 4 hours after this period the replenishing rate is still better than normal, but not as good as during the first 2 hours.  Six hours after training the glycogen storage rate is back to normal.

The amount of carbohydrate to be consumed in the ‘window’ period is recommended at about 1 g/kg body weight. Weighing 70 kg, for example, you would need to consume 70 g carbohydrate within the 2 hours of exercise. It is very important to start refuelling after exercise, even if you trained late at night. In this case make your evening meal light and easily digestible – a liquid meal (shake or meal replacement) may be appropriate, or you could consider fruit and nuts.  Post-exercise replenishing may be of moderate or high GI-carbohydrates, especially if you are training intensely everyday or training twice a day. Studies suggest that consuming a protein carbohydrate drink promotes muscle glycogen levels if consumed within the first few after hours after exercise.

It is crucial to include protein in your post-exercise meal or drink. The stress of exercise and especially the typical plyometric exercises found in Taekwondo, such as explosive kicks and jumping techniques, worn muscle tissue. Protein is needed to rebuild and grow muscle tissue.  Food between workouts?  It is firstly important to make use of the 6 hours directly after training, specifically the ‘window’ period.

To optimise glycogen replenishment, you should ensure a relatively steady supply of carbohydrates into the bloodstream. The best way to ensure this is to make use of low GI-foods.  Although it is sometimes suggested to have more small meals throughout the day, another suggestion is that the digestive system, specifically the stomach, should have periods of rest between meals – about 4-5 hours between meals

Carbohydrate loading

Carbo-loading is recommended as advantageous for endurance events lasting longer than 90 minutes, and events that involve several matches over a short period, such as sparring bouts at tournaments. Carbo-loading is used to increase the muscle glycogen stores to higher than normal levels, which in theory should allow for a greater supply of energy; in other words, longer activity with delayed fatigue.

On day 1, carry out endurance training for about 1 hour to reduce the amount of glycogen in your liver and muscles. For the following 3 days, taper your training and eat a moderate-carbohydrate diet (5-7 g carbohydrate/kg body weight). On the final 3 days you should continue tapering your exercise or rest, while increasing your carbohydrate intake to 8-10 g/kg body weight. You may gain about 1-2 kg during carbo-loading.