The benefits of carbohydrate ingestion before and after prolonged exercise are well known to scientists, coaches and athletes alike. However, the type of carbohydrate consumed can have a significant effect on substrate metabolism both at rest and during exercise. The glycaemic index (GI) is a method of classifying carbohydrate-containing foods according to their postprandial glycaemic responses. This is a useful tool to aid the selection of appropriate carbohydrates for both pre- and post-exercise meals. This thesis examined the influence of ingesting mixed meals with different glycaemic indices both before exercise and during the post-exercise recovery period in male and female subjects.