Fluid and Fuel Considerations for Marathon Running

by Clare Wood, Sports Dietitian

The marathon is one of the premier events of the Olympic Games. It is a grueling 42km running race which tests athletes to the max. It is important for athletes to be well prepared, mentally, physically, and nutritionally. There are a many nutritional strategies that can be followed before and during the event, such as those listed below. It is interesting to compare the refelling methods of the marathon runners today to those of previous Olympic Games marathon competitors. See also Clare's Top-10 Nutrition Strategies for Marathon Runners.

Carbohydrate Intake

For optimal performance during any event that is more than 90 minutes in duration, such as a marathon, it is crucial to take in carbohydrate during the race. Doing this will minimize fatigue, and spare muscle glycogen during the race so that muscle fuel stores will last longer.

The maximum rate for stomach uptake and metabolism of glucose for use in the muscles is approximately 1g/kg body-mass/hour. So for an athlete of about 70kg, this would be 70g/hour. For some people it is difficult to take this amount in during a race, so this guideline is an upper limit.

Fluid Intake

Hydration is vitally important for optimal performance and health, particularly in hot and/or humid conditions. Your level of fluid intake is dependent on your specific sweat rate (see calculating sweat rate). However, for a guide, taking in about 200ml every 20 minutes is the current guidelines. This works out to be about 600ml per hour. Spillage is also a big factor when planning fluid intake compared to actual intake during the race.

exhausted athlete finishing the raceThere are many alternative food and exercise strategies that can help to combat fatigue.

Sodium Intake

Sodium replacement is essential for endurance events. Replacement of between 0.25g per hour for those athletes who are susceptible to cramps, or 0.5g per liter of fluid for exercise activities lasting greater than one hour. Gastrolyte or a similar electrolyte replacement product you can buy from most pharmacies (drug stores). When it is made up to packet directions (one sachet for 200ml of water), it will provide this amount of sodium for 100mls. Check the label.

Tip: Practice strategies for your race during training, such as various pre-race meals, and various foods and fluids during training

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