NUTRITION AND PERFORMANCE Stacey Meates Alicia Ritchens Sally Barnes Elise Kealy

Types of carbohydrates There are three main types of carbohydrates; Monosaccardides, these are one-unit sugars like glucose, frutose & galactose. Monosaccardides cannot be broken down to a simpler form as they only contain one bond. Disaccharides, such as sucrose, lactose and maltose. These are two bond CHO’s, when broken down they form monosaccardides. Polysaccharides, are large chains made up of many monosaccardides. These CHO’s are found in animals, stored in the liver and muscle.

Role of Carbohydrates in Sport. When you consume carbohydrates, the excess are converted to glycogen (gluconeogenesis), the majority of which is stored in the liver or muscles. The glycogen stored in the muscles is the main source of energy for most athletes, so their total calorie intake should include around 50% carbohydrates. It is when the glycogen storage in muscles is exhausted that an athlete will experience muscle fatigue. Eating a high carbohydrate diet the body will store twice as much glycogen, compared to a low carbohydrate diet, thus significantly reducing the chance of muscle fatigue.

Glycaemic Index The glycaemic index (GI) refers to how quickly the body can break down the carbohydrates in a food, and store them as glycogen in the body. When the carbohydrates are consumed, the body releases insulin to convert them to glycogen. Foods with a low GI are slow to be stored, compared to foods that have a high GI and are quickly stored away. When a food has a high GI, the body releases a lot of insulin quickly to break down the carbohydrates, so you go from experiencing a lot of energy to none at all. (Easy to remember – Foods with a high GI, will leave you on a sugar high). A foods GI is generally related (although not always) to the type of carbohydrate it is. Eg. Monosaccharides only have one bond so are easy to breakdown. Therefore they have a high GI.

Hypoglycaemia A decreased blood glucose level Hypoglycaemia occurs occasionally during exercise and can be caused by many factors including working at a level that’s too hard for your body or inadequate nutrition. It can also be triggered by external influences such as high temperature. Hypoglycaemia can be prevented by eating an adequate pre-exercise meal containing the right amount of carbohydrate depending on the exercise you are about to complete. Hypoglycaemia obviously has a negative effect on an athletes performance as it results in extreme fatigue as blood glucose levels are so low, it takes longer to produce the energy the body requires.

Hyperglycaemia An elevated blood sugar level Hyperglycaemia occurs when there is a rapid increase of glucose in the blood because there is not enough insulin to break the glucose down. It can be prevented again by ensuring that your pre exercise meal is well balanced and doesn’t contain a large amount of High GI carbohydrates. Hyperglycaemia also has a negative effect on an athlete’s performance as it has many symptoms including increased thirst, and hunger and blurry vision.

Rebound Hyperglycaemia When an athlete experiences a high followed by an extreme low in energy. Rebound hyperglycaemia occurs when high GI foods are consumed mins before exercise. This makes the body’s blood glucose level rise rapidly and in response the body excretes insulin quickly to convert the glucose into glycogen to be stored in the muscles. This quick response causes the body to fatigue as there is less glucose in the blood that can be used as fuel for exercise. Rebound hyperglycaemia can be avoided by ensuring that high GI foods (over 6% CHO) are not consumed before an event.

Blood Glucose Loading. Blood Glucose Loading is the consumption of food on the day of competition. This can help replenish any energy stores that may have been depleted during the night and even help in the recovery from the previous training session. It’s important for athletes to know which foods will help them perform at their peak level. Foods should be low GI and high in CHO to help sustain energy levels during exercise. Foods to intake before an event include fruit, cereals, pasta and rice. Food to avoid is anything high in fat, fibre, green acidic vegetables, salty foods and caffeine, as these can be hard to digest or can make the body uncomfortable.

Carbohydrate loading CHO loading is a change in nutrition and training in the 3-4 days leading up to an endurance event. These 3-4 days before an event the athlete will taper their exercise and increase their CHO intake. A meal that an athlete may consume for breakfast when CHO loading would be high fibre cereal, a banana and a fruit smoothie with low fat yogurt. According to the Australian Institute of Sport (AIS) carbohydrate loading can improve performance by 2-3%, this is only possible if carbohydrate loading plans are carried out accurately.