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This summary is from the IAAF 2nd International Consensus Conference on “Nutrition for Athletics“ held in Monaco from April 18-20, 2007. Copies of the CD and booklet are available from the IAAF website www.iaaf.org.
Nutrition for Long-Distance Running
Presenter: Louise Burke (AUS)
Over history, long-distance running has been in the front line of sport nutrition research and application. The introduction of carbo-loading in the late 1960s was one of the first well known nutrition strategies for enhancing performance. Since then, the technique has evolved into a two-to three-day protocol and recently, supra-maximal glycogen stores, comparable to the values previously reported, have been shown after just 36 hours.
Long-distance runners are characterised by high maximum oxygen uptake, very low levels of body fat and minimal muscle development of the arms and upper torso. Especially “hot weather” race winners tend to be small and light. Females usually have to push their body weight further from their natural shape than male runners. However, the penalty is also greater. Some develop eating disorders, osteopenia and chronic menstrual dysfunction.
The carbohydrate needs of distance runners are complex and multi-factorial. Some studies that have shown benefits of training in a low glycogen state, however, there are well described potential disadvantages of this strategy such as increased risk of illness or injury, reduced capacity to train and reduced well-being. Training in a low glycogen state is not recommended at this time and distance runners should follow established carbohydrate intake guidelines.
Protein requirement is elevated by long distance running and can be nearly twice the requirement of sedentary people (1.7g/kg/ day). Nitrogen balance can be influenced by timing of protein intake, with better maintenance of nitrogen balance when protein is consumed after exercise.
Fat adaptation has been researched extensively, but no positive performance outcomes have been shown. A reduction in the ability to perform high intensity exercise has been shown. Fat adaptation should not be undertaken by marathon runners.
Fluid and carbohydrate should be consumed during races of 60 minutes and longer. The concentration of carbohydrate can be varied between 4 and 8%, according to priority of re-hydrating or re-fueling. It is not recommended to give more than 60 grams per hour, although higher absorption rates have been reported with mixed carbohydrate forms. However, this study was done in cyclists and the overall impression is that higher intakes would cause GI distress in most individuals. It was noted that the GI tract is highly adaptive and can get used to high carbohydrate and fluid intakes. This might be worth training, especially for marathon runners.
Iron deficiency often occurs in long-distance runners. Although there does not seem to be a higher incidence than in the general population, iron deficiency can hinder performance and should be avoided. Regular screening of serum ferritin is warranted. Iron supplementation should only be commenced after diagnosis of low serum ferritin and/or low haemoglobin. At this time there is no certainty about whether intra-muscular iron injections offer advantages over oral iron supplementation. However, there is a risk of anaphylactic shock and iron overload, so oral iron supplementation should be preferred.
The only supplement to have shown consistently beneficial effects on long-distance running performance is caffeine. Doses of 3-5mg/kg show similar effects to doses of 7mg/kg. However, doses of 9 mg/kg actually hindered performance.
The above summary was written by Peter Res
If you wish to download this handy Grams and Calorie Calculator for Carbohydrate, Protein, and Fat, click here for the Excel spreadsheet.
This is part 4 of 14 in a series from the 2007 2nd IAAF International Consensus Conference “Nutrition for Athletics”