Long gone are the days when athletes thought that eating a big steak before a game would give them lots of energy. Today's elite sports men and women follow a strict diet, particularly on the day of a competitive match or event. While diet won't turn poor athletes into great ones, it can make the difference between performing poorly and tapping your full potential.
Not all carbohydrate is digested and absorbed at the same rate. The Glycemic Index (GI) is a scale of how much a particular type of food raises blood sugar over a two-hour period compared to pure glucose.
For example, a piece of food with a GI score of 45 means that it raises blood sugar 45% as much as pure glucose in that two-hour period.
Common sense says that simple sugars which are broken down quickly, like fructose in fruit, should have a higher GI than complex carbohydrates, but that's not always the case. White bread, white rice and potatoes (all classed as complex carbohydarets) have a very high GI. That means they raise blood sugar almost as much or even more than pure glucose. Fructose has medium GI because the fibre found in fruit slows digestion and absorption.
Choosing foods with a high GI will help to quickly replenish carbohydrate stores after a game or event. Before a game or event, low GI foods are more appropriate as they release energy more slowly and for a longer period.
The goal prior to a game or event (and even a training session) is to maximise carbohydrate stores in the muscles and liver and to top up blood glucose stores. Studies have shown that consuming foods with a high GI within an hour of exercise can actually lower blood glucose, which is not what an athlete wants! The reason is because the body produces an "overshoot" of insulin, which helps muscles to take up sugar in the blood. This in turn causes low blood sugar levels.
Athletes should eat foods with a low to medium GI before a match. This allows for a relatively slow release of glucose into the blood and avoids the unwanted insulin surge.
Consuming carbohydrate at least an hour before the start allows any hormonal imbalance to return to normal.
Example low GI foods include pasta, whole grain breads and rice, oatmeal, milk and milk products and fruit (except bananas and dried fruit).
The pre-match meal might consist of pasta in a low-fat tomato sauce, baked beans or scrambled eggs on toast and fresh fruit such as apples, pears or orange juice. Some grilled fish or chicken and vegetables could accompany the carbohydrates. Ideally this meal should be eaten at least three hours prior to the start - especially if nerves are a factor, which can impair digestion.
Food in the stomach is given a high priority to be digested before it has chance to spoil. As a result greater blood flow is directed to the digestive tract - not good news when players' muscles will soon be demanding an increase in blood flow too. The result of performing with a full stomach is nausea - the body's attempt to cease exercise so that it can redirect blood flow back to the stomach.
There is one exception to consuming carbohydrate immediately prior to the start of a game and it's in the form of a sports drink 5 or 10 minutes before kick off. This is discussed in more detail in part 6 tomorrow.
As an example, soccer players can use up 200 to 250 grams of carbohydrates during a game. It's important that they (and other athletes that perform for a similar duration) replenish those stores as quickly as possible. It becomes even more important if the athlete has more than one competition in the week or are involved in heavy training.
Ideally, a large, high-carbohydrate meal should be eaten within two hours of the finish and it can and should consist of high GI foods. Bananas and dried fruits are good immediately following a match, as are sandwiches and high-carbohydrate drinks like Gatorade Exceed and Lucozade. A main meal several hours later might consist of bread, pasta, potatoes and rice as well as other simple sugars like cakes and sweets.
Even under the best circumstances it can take over twenty hours to fully restore carbohydrate stores. This has implications for athletes who are competing five or six days a week (perhaps during a tournamnet). In this case carbohydrate replenishment at regular intervals during training sessions becomes very important. This is where high-carbohydrate drinks can offer a real advantage (see Part 6 tomorrow).
Carbohydrate loading is often used by long distance athletes to "pack " their muscles with energy. The actual process involves depleting the muscles of carbohydrate a week or so before the event with exhaustive exercise and a low-carbohydrate diet.
Two to three days before the event the athlete switches to a very high-carbohydrate diet. In their depleted state, muscles take up more carbohydrate than they normally would giving the athlete a large store of energy.
For most sports and events, carbohydrate loading is unnecessary. In fact a disruption in an athlete's normal eating pattern can actually cause stomach upset and lead to impaired performance. A more sensible approach is to increase carbohydrate intake in the days leading up to a game or event.