Surviving the Dusi

2013-02-14 00:00

THIS morning saw the beginning of our city’s flagship canoe race — the Dusi Canoe Marathon.

For each Dusi participant, maintaining energy levels over the next three days of gruelling activity takes careful planning. Providing the body with adequate fuel to sustain high levels of performance is one of the challenges in any sport lasting longer than a couple of hours.

When you exercise, numerous changes occur in your body. Muscles contract much more intensely, the heart beats faster to deliver blood more quickly to the rest of the body, and the lungs work harder to provide the exercising muscles with more oxygen. These changes demand an increase in energy supply, which must be met to prevent fatigue. For the first five to 15 minutes of exercise the body makes use of glycogen stores (essentially, carbohydrates stored from your diet). As your heart and lungs work harder, more oxygen is supplied to the body and you are able to start using other energy sources. After this initial five to 15 minutes (depending on diet and fitness level), your body starts using proportionally more fat and less carbohydrates. This scenario occurs if your breathing and heart rate have consistently and gradually increased, allowing increased oxygenation of the tissues.

However, if you start exercising too strenuously too quickly, the oxy­gen supply cannot keep up with the demand, which will result in an excess lactic acid build-up. This brings early fatigue and you will have to reduce your pace considerably or even stop. Warming up before the race starts (or before any exercise for that matter) will cause your heart and lungs to start working harder and you can then head out at optimal speed from the start.

In endurance events, such as the Duzi Canoe Marathon, that last for a number of hours and continue on successive days, maintaining good hydration and blood-sugar levels is a challenge that must be met.


Carbohydrates are an essential fuel source for almost all types of activity and sport. The amount of carbohydrates in your diet will determine how much glycogen your body has in storage. Glycogen is the fuel that muscles require as exercise begins. Eating inadequate carbohydrates will result in depleted glycogen stores and you will not be able to exercise at your optimal intensity.

During exercise periods lasting longer than an hour, it is important to consume some form of carbohydrate to delay fatigue and ensure you can continue once muscle glycogen stores are depleted. The minimum amount you would need to consume every hour is 500 millilitres of a sports drink, or 250 ml of fruit juice diluted with 250 ml of water, or one large banana, or a handful of raisins, or one energy gel sachet. This amount can be doubled if you are exercising at a high intensity, but there is no benefit in consuming any more than the doubled amount.

Consuming adequate fluid is a constant challenge for paddlers, as carrying enough water or hydration fluids in the canoe is not practical or feasible. Ideally, one litre of fluid per hour should be consumed.


For the first two hours after exercise, glycogen storage is at its highest. It is therefore essential to eat as soon as possible after activity to ensure adequate refuelling. This is essential to ensure good energy levels for paddling through day two and day three. Sports drinks, jelly babies and dried fruit are quick and easy snacks to begin the refuelling process. Consuming some protein will also help to speed up muscle repair. Sandwiches (with tuna or chicken, or peanut butter), yogurt, a glass of fresh milk or jacket potatoes with cottage cheese are some useful options to eat within the first two hours.

As a rule of thumb, when you weigh yourself after a long exercise session, you should not have lost more than two kilograms of body weight. Losing more than this amount of weight indicates that you are dehydrated and have not consumed adequate fluids.

Sports drinks may be more beneficial than water for recovery after exercise. Drinking plain water will quench your thirst earlier and thus you may stop drinking before you are rehydrated. The presence of sodium in a sports drink stimulates thirst and keeps you drinking. It also reduces urine production, allowing your body to retain more of the fluid.

Consuming adequate fluids and carbohydrates is crucial for peak sports performance and can be as essential as sufficient training.

I wish all Dusi participants a successful race and a speedy recovery.


• Sharon Hultzer is a consulting dietitian. She can be reached at eats

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