Carb Loading, Glycemic Index and Glycemic Load Nelson PE pages 93 and 94, 345 and 347

Food Fuel used during exercise and rest. Carbohydrates – preferred fuel source during exercise. Contribute about 1/3 of energy at rest. Fats – preferred fuel source at rest (contribute 2/3 of energy). Also used during sub-maximal exercise in addition to carbs. Protein – usually used for growth and repair but is used as a last resort if the body is starved of other sources.

Glycemic index Glycemic index (GI)- measure how quickly a food releases sugar into the bloodstream. Low glycemic index foods are better to eat before physical exercise because the energy last longer. Glycemic load – GI x carbohydrates in grams per serving.

Basal metabolic rate The amount of energy used at rest.

Factors that affect GI Fatty foods can delay stomach emptying and slow release of sugar into the blood. Organic acids can lower GI e.g. vinegar Physical entrapment of sugars within food. Type of starch involved.

GI and endurance sports Low GI foods should be consumed 45 to 60 minutes before exercise. High GI food reduce performance if consumed in this period. High GI foods need be consumed immediately before exercise.

Carbohydrate loading In sports such as marathons where you exert yourself for long periods without a chance to refuel it carb loading is a strategy used to make sure there is stored carbs available for the body to use. Not useful for teams sports where you have a chance to eat and only exert yourself in bursts.

Practical exercise Look at cereal boxes and work out the GI and GL.