I hope this article is timely for fellow runners and duathletes who are preparing for the Army Half Marathon on 11th September 2005, Powerman Malaysia on 25th September 2005 as well as those looking forward to the Stanchart Marathon on 4th December 2005.

Why carbo-load?

You may want to refer to my other article “How to Exercise Effectively to Lose Fat”. The only source of energy for muscle contraction is ATP which can be derived from 3 energy systems, namely: ATP-Phosphocreatine, anaerobic glycolysis, and aerobic glycolysis. Carbohydrate and muscle glycogen are used as fuel in the anaerobic and aerobic glycolytic pathways. In endurance exercise, aerobic glycolysis is the main pathway used to provide energy.

Our muscles have limited capacity to store glycogen, which is derived from the carbohydrate we consume. Usually, this is not a problem. However, once we start to exercise at high intensity, such as when running or swimming, and this continue for more than 60 to 90 minutes, our muscles run out of glycogen. As a result, our stamina and performance diminish.

Muscle glycogen levels are normally in the range of 100-120 mmol/kg ww (wet weight). Carbohydrate loading enables muscle glycogen levels to be increased to around 150-200 mmol/kg ww. 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 carbo-load?

Carbohydrate loading is not for every athlete. But if you want to improve your performance in a high-intensity aerobic endurance event, carbohydrate loading might help.

Long-distance running and swimming, soccer, canoe racing and triathlons are appropriate activities for carbohydrate loading. Shorter runs, such as a 5- or 10-kilometer race, weightlifting, and recreational biking or swimming are not.

Carbohydrate loading does not increase endurance unless you are a highly-conditioned athlete. Eating extra carbohydrates will not store extra muscle glycogen unless the enzymes in muscles are primed by regular hard exercise. Carbohydrate loading in non-competitive athletes stores extra fat.