Endurance Nutrition

To train and perform at your best, nutrition and hydration play a crucial role that can make or break your performance. You need to have an eating strategy in place for before, during and after training and competitions.

Pre Race Nutrition

Depletion of stored carbohydrate (CHO) is a major cause of fatigue during long duration exercise, so optimizing CHO status before exercise is the primary goal of pre exercise nutrition. CHO loading aims to maximize muscle glycogen stores prior to a competitive event. The decision to CHO load requires careful consideration and planning as it requires 3-5 days of CHO between 7-10g per kg of body mass per day or 70-85% of energy. CHO loading doesn't appear to be beneficial in events lasting less than 60-90mins, although it is important to have 24 hours rest prior to an event and to eat adequate CHO. Females may be less responsive to CHO loading due to relatively unknown causes and it is difficult to compare the genders when you have to account for the many differences.

A pre-event meal should be consumed 1-4 hours prior to competition with the aim to top up muscle glycogen, restore liver glycogen (especially after overnight fasting), prevent hunger while avoiding gastrointestinal upsets and ensuring adequate hydration. This meal should be high in CHO rich foods and drinks. Foods that are low fat, low fibre and low-moderate protein are preferred for pre-event as they are less likely to cause any gastrointestinal problems. Low glycaemic index CHO are favorable to provide a sustained release of CHO during endurance events, although effects differ between individuals. If it is unpractical to consume a substantial meal before an event, especially if you have an early morning start, settle for a lighter meal and consume CHO throughout the event. Consume 300 to 600 mls of fluid with your pre-event meal and continue to take in small amounts of fluid up until 30 mins before the event to allow for one last toilet stop.

Adequate hydration is crucial as endurance events pose a significant risk to dehydration. Often sweating rates exceed the rate of ingestion of fluids, especially in hot humid environments. In order to minimise dehydration, athletes need to consume extra fluid in the days leading up to an event and drink enough during exercise to match their sweat losses. Sweat loss can be determined by weighing yourself before and after exercise. Each kilogram of weight loss indicates 1 litre of fluid loss. Adding the amount of fluid consumed during the exercise session, gives total fluid loss for the session. For example, if an athlete finishes an exercise session 1kg lighter and has consumed 1 litre of fluid during the session, total sweat loss equals 2 litres. Once an athlete's average sweat loss is known, a plan can be prepared to enable the athlete to match sweat losses in subsequent exercise sessions. Be prepared to consume extra if the weather is hot and humid as this accelerates sweat loss.

Nutrition and hydration during events

Water is adequate for hydration for shorter events, but sports drinks can help meet both fluid and CHO needs for events lasting longer than 60 minutes. The sodium in these sports drinks helps stimulate thirst and enhances water and sugar uptake in the small intestine more than just plain water. They therefore assist in keeping hydration levels up, replacing sodium lost in sweat and providing some CHO for energy. Sports waters are a relatively new concept designed for people who don't require the extra CHO as they are only exercising at a low intensity or for those who don't enjoy the taste of water and require a slight flavour to encourage fluid intake.

Ingesting CHO during the event can help offset fatigue and improve performance. It has been shown that ingesting small amounts often is better than a large amount at the onset of fatigue as maximum rate that ingested CHO can be used is about 1g per minute. So plan to consume 30 - 60g of CHO per hour (375 to 100mls of most sports drinks), again remembering that everyone is different and it is best to trial different amounts during training sessions to see which amount maximizes your performance.

For prolonged events you may need to consume more than just sports drinks to provide extra fuel. CHO rich foods such as sandwiches, muesli bars, chocolate bars, jelly beans or bananas are your best choice as fuel sources. Choose foods that will provide you with the energy you need while considering the practical implications. Important issues to consider are do you carry supplies with you, or do you take what is offered on the course which requires stopping at the drink stops thus slowing you down. Cyclists generally find it easier than runners to consume food during races due to the body not being bounced up and down. It is important to not try anything new on race day as gastrointestinal upsets are unpleasant especially if you are only at the half way mark. Find out what sports drink is going to be available during the race and practice using it in training. It is important to drink as much as practical and comfortable while attempting to match sweat losses. It may be useful to change flavours in prolonged events to avoid 'flavour fatigue'.

When exercise duration is very prolonged (>6 hours) and excessively large amounts of low sodium drinks are consumed during exercise, hyponatraemia can occur. This is when the concentration of sodium drops to a dangerously low level in the body and the bodies electrolyte balance is thrown off. Knowing your sweating rate and accounting for sodium losses can help you plan your hydration throughout your event. If you perspire heavily or are participating in an extremely prolonged event where large sodium losses can be expected, salt tablets may be required.

Post Nutrition

Recovery goals are to restore liver and muscle glycogen stores, replace fluid and electrolytes lost in sweat and repair any muscle damage caused by the exercise. It is important to maximize recovery if you have less than 8 hours between exercise sessions so begin consuming high CHO food within 30mins of a competing session. Rapid resynthesis of glycogen is aided by immediate intake of carbohydrate (0.7 - 1g per kg of body weight every 2 hours leading to a total of 7-10 g/kg body weight over 24 hours). Choose high carbohydrate foods such as white bread, sports drinks, bananas, white rice etc. that are high GI. A small amount of protein with your recovery meal can help promote faster muscle repair. If appetite is suppressed or gastrointestinal problems are evident, focus on low fibre, high sugar sources such as sports drinks or lollies.

Rapid rehydration can be achieved by consuming 1.5 times the volume of fluid lost over the subsequent 2-4 hours (taking into account the fluid consumed during event). In large fluid deficits (>2 litres), sodium replacement will assist in the absorption and retention of fluids.

Forming a nutrition plan can take a bit of time, but the results will be worth it. Read nutrition labels, test products and amounts during training sessions and work out what your individual needs are.


By
Michelle Blunden BPhEd, BSci
 


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