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

The main source used for this article is The Complete Guide to Sports Nutrition by Anita Bean (2003). This article can be considered as a collage of direct summaries of selected sections from Bean’s book. The Complete Guide to Sports Nutrition is published by A & C Black Publishers Ltd (37 Soho Square, London W1D 3QZ) and can be ordered from their website: http://www.acblack.com. Health Power: Healthy by Choice, Not Chance by Aileen Ludington and Hans Diehl (2000) is another influential source, published by Review and Herald Publishing Association (http://www.reviewandherald.com) and can be ordered at http://www.adventistbookcentre.com. This article is for personal use only and may not be used for commercial means. The author, affiliates and sources referred to, cannot accept responsibility for any injury or loss sustained as a result of the use of this material. Always consult a professional health practitioner before making any lifestyle changes.

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

Energy

Energy can be produced from the following four food (or drink) components:

• Carbohydrates
• Protein
• Fat
• Alcohol

When consumed, these components are broken down into various building blocks, and then taken up into the bloodstream and through different processes they are converted into energy. Carbohydrates are broken down into mostly glucose, as well as fructose and galactose. Fats become fatty acids, proteins amino acids and alcohol is mostly absorbed directly into the bloodstream.

Carbohydrates and alcohol are used for energy in the short term. Fats are used as a longterm energy reserve. Proteins are only used as an emergency energy source, or when the amino-acid has reached the end of its usefulness it is recycled for energy.

Only carbohydrates, fats and proteins are used for energy during exercise. Alcohol cannot be used directly by muscles. Proteins, as well, is not a main contributor to energy. It is only during very prolonged and extremely intense sessions (such as a marathon), or during semistarvation, that proteins are likely to be used. The main energy contributors are carbohydrates and fats. Fats only really come into play after a relatively long period of activity (after about an hour or two). The chief dietary source for energy is therefore carbohydrates.  The main form in which carbohydrates is stored in the body is as glycogen.

The energy one uses in sport activities are mostly derived from glycogen stored in muscles.  Glycogen is converted into glucose which in turn is changed into ATP (adenosinetriphosphate) which is the energy-currency used by your cells. A high muscle-glycogen level
will allow for better training intensity. Low muscle-glycogen has the opposite effect – earlier fatigue and reduced training intensity.

There are three energy systems used for different kinds of physical activity:

The ATP-PC system is used for energy bursts lasting for a couple of seconds (about 5 seconds). This is the energy system you are most likely to rely on in a self-defence situation, where you suddenly need a burst of speed and strength and using only a limited amount of techniques for retaliation. Another example where this system is used is during a single power-break technique, done cold (without a warm-up).

The anaerobic glycolytic system kicks in the moment you start a high intensity activity, lasting up to 90 seconds, such as a 400-800 meter sprint, during a tournament sparring session, a pattern performance, self-defence demonstration or actual self-defence. This system uses carbohydrates in the form of muscle glycogen or glucose as fuel.

Activity lasting longer than a few minutes will switch to the aerobic system. This system is slightly slower than the other two to provide ATP, but it can produce larger amounts. This system uses a mixture of carbohydrates and fat to produce energy. Typical training in a dojang that lasts for about an hour to two hours relies on the aerobic system for energy.

Your muscle glycogen will be able to keep you going for about 90-180 minutes of endurance activity (e.g. Jogging). The higher the intensity, the faster the muscle glycogen stores will be
depleted. Interval training, i.e. a mixture of endurance and anaerobic activity, which is typical of Taekwondo training, will last about 30-45 minutes before muscle glycogen is depleted.

The moment muscle glycogen is depleted, your muscle protein starts to break down to supply your energy needs. The fitter you are aerobically the more your body is able to use fat instead of glycogen to supply in your energy needs. Improved aerobic fitness enables you to break down fat at a faster rate at any given intensity, therefore allowing you to spare glycogen.

The higher your carbohydrate intake the higher will be your muscle and liver stores of glycogen. Low muscle glycogen will use more fat, but also more protein. This is not good because you will loose lean-muscle in the process. In other words, low dietary carbohydrates
ultimately result in weaker muscles.

Taekwondo training in the typical dojang usually revolves within numbers 2 – 4. Real selfdefence scenarios will mostly rely on numbers 1 and 2. Some crucial questions should be asked about why Taekwondo spends so much time on aerobic fitness, when both selfdefence and tournaments rely mostly (although not exclusively) on anaerobic fitness; but that is for another article.

This is the crux: Glycogen is used during almost all activities. The greater your pre-exercise muscle glycogen store, the longer you will be able to maintain the intensity of your activity and the longer you will delay fatigue. Therefore, as a sportsperson, it is crucial to make sure you have enough carbohydrates in your diet.