Issue: Volume 28 Number 3
Foods and fluids consumed in the four hours prior to competition complete an athlete’s nutritional preparation. The pre-event meal adds to muscle glycogen stores if they have not been fully restored since the last exercise session. It also restores liver glycogen for early morning events, ensures the athlete is hydrated and prevents hunger. Food choice also impacts on gastrointestinal comfort and the athlete’s psychological outlook.
Timing of carbohydrate intake
Individual tolerance and competition schedule dictate the ideal timing for the pre-event meal. General guidelines suggest a meal or series of snacks should be consumed 1–4 hours prior to exercise. The longer time frame allows carbohydrate intake to contribute to liver and muscle glycogen stores. However, early morning events often mean a shorter time frame is more practical. A small proportion of athletes respond negatively when carbohydrate is consumed close (within one hour) to exercise. An exaggerated carbohydrate oxidation and subsequent decrease in blood glucose concentration at the start of exercise can cause symptoms of hypoglycaemia, including fatigue.
The exact cause is unknown but useful strategies for these athletes may be to allow longer between eating and exercise, consume a substantial amount of carbohydrate in the pre-event snack (more than 1g per kilogram body mass or ~ 70g for the typical athlete) and include low-glycaemic index (GI) foods in the pre-event meal. Athletes who experience gastrointestinal problems during exercise may also benefit from allowing a longer period of time between eating and exercise.
Amount of carbohydrate
Research suggests that endurance performance is improved when athletes consume a substantial amount of carbohydrate (200–300g) in the 2–4 hours before exercise. This is achievable when events are held later in the day but is not always practical before early morning events. In many situations athletes must settle for a smaller meal or snack before the event, then make up for lower than recommended carbohydrate intakes by consuming carbohydrate during the event.
Type of food
The carbohydrate foods most suited to pre-exercise eating are low-fat, low-fibre and low to moderate in protein; these are less likely to cause gastrointestinal upset. Liquid meal supplements (such as PowerBar ProteinPlus Powder Drink) or carbohydrate-containing sports bars (such as PowerBar Performance Bar) can be useful for athletes who suffer from pre-event nerves or have an unpredictable pre-event timetable.
Consuming low-GI foods has been proposed as a clever pre-event strategy for endurance events. GI is a measure of the blood glucose response following ingestion of carbohydrate-containing foods. Foods with a high GI are digested and absorbed more rapidly by the body, delivering glucose quickly into the bloodstream. Foods with a low GI are digested and absorbed more slowly, resulting in a gradual release of glucose. It is thought that low-GI foods might reduce the sudden increase in blood glucose levels prior to an event, and prevent the subsequent drop in blood glucose once exercise commences. In addition, a low-GI pre-event meal might provide a continued supply during the exercise session.
In general, studies have failed to show a universal benefit to performance from consuming low-GI foods prior to exercise. When carbohydrate is consumed during exercise according to sports nutrition guidelines, any effect of consuming low-GI foods in the pre-event meal is negated. When fuel cannot be consumed during a prolonged exercise session, some athletes may derive benefits by consuming a low-GI pre-event meal. However, for most occasions, the athlete can choose the foods consumed in their pre-event meal based on personal preference, availability and gastrointestinal comfort.
Examples of low-GI foods (GI value <55)
- Pasta served with a mixed bean pasta sauce
- Vegetable curry made with vegetables and lentils
- Fresh fruit, such as apples and oranges
- Full-cream or low-fat yoghurt
- Fruit smoothie made with milk and/or yoghurt
- Wholegrain sandwich made with Burgen ® Soy and Linseed bread
- Breakfast cereal (such as All-Bran ® Fruit ‘n Oats) plus low-fat milk
- Stir-fry of lean meat and vegetables served with boiled basmati rice
Dehydration causes fatigue, impaired muscle endurance, reduced gastric emptying and impaired mental functioning. Fluid deficits as little as 2 per cent body mass may cause measurable impairments in performance, with the degree of impairment increasing directly in proportion to the fluid deficit. Even with model drinking practices, athletes find it difficult to keep pace with rates of fluid loss during exercise. A key strategy to minimise the effects of dehydration is to correct any fluid deficit before commencing exercise.
In normal circumstances, thirst is a sufficient stimulus for adequate fluid intake. However, when following a heavy training schedule, especially in challenging environmental conditions, athletes need to be more aggressive with fluid intake. Hyperhydration (with or without glycerol) may be warranted in some cases. This should always be planned and monitored with the aid of an experienced sports science professional.
Most athletes can tolerate a large amount of fluid immediately before exercise (about 5ml per kilogram of body weight or 300–400ml) and then adopt a pattern of consuming small, frequent amounts of fluid during exercise. While water is suitable for adequate hydration prior to shorter events, the use of sports drinks may assist in meeting both fluid and carbohydrate needs before longer events.
Suggestions for pre-event food and fluid intake
Two to four hours prior to exercise:
- Pasta/rice with low-fat pasta sauce
- Fruit salad with low-fat yoghurt
- Baked potato served with baked beans
- Meat/salad sandwiches
- Toast with jam and sports drink
- Crumpets or English muffins with jam/honey plus fruit smoothie
- Breakfast cereal with low-fat milk plus tinned fruit
- Lean meat, vegies and noodle stir fry
- PowerBar ProteinPlus Powder Drink plus PowerBar Performance Bar
Sixty minutes prior to exercise:
- Sports drink
- Cereal/muesli bars plus banana
- PowerBar Performance Bar or PowerBar PowerGel plus sports drink or water
- Vegemite sandwich plus juice and fruit
Gisolfi, C 1996, ‘Fluid balance for optimal performance’, Nutrition Reviews, 54(4), pp. S159–67.
Hargreaves, M 2001, ‘Pre-exercise nutritional strategies: effects on metabolism and performance’, Canadian Journal Applied Physiology, 26, pp. S64–70.
Hawley, JA and Burke, LM 1997, ‘Effect of meal frequency and timing on physical performance’, British Journal of Nutrition, 77, pp. S91–103.
Moseley, L, Lancaster, GI and Jeukendrup, AE 2002, ‘Effects of timing of pre-exercise ingestion of carbohydrate on subsequent metabolism and cycling performance’, European Journal of Applied Physiology, 88, pp. 453–8.
Walsh, RM, Noakes, TD, Hawley, JA and Dennis, SC 1994, ‘Impaired high-intensity cycling performance time at low levels of dehydration’, International Journal of Sports Medicine, 15(7), pp. 392–8.
Reproduced with permission from Current Concepts in Sports Nutrition by the Sports Nutrition department of the Australian Institute of Sport. This booklet was produced with assistance of Powerbar. It is available via the AIS Nutrition web site at http://www.ausport.gov.au/ais/nutrition.