Fuel for a runner’s marathon effort

Press, 31 May 1982, Page 13

Fuel for a runner’s marathon effort

Jaiiice Bremer concludes her series on food for marathon runners with advice for race day.

Good eating

Janice Bremer DIETITIAN

Current studies suggest that the time between the last “carbohydrate" meal and the race, has a bearing on the use of carbohydrate by muscle during the race. This meal should be.three to eight hours before the event. Food must empty rapidly from stomach and not cause bowel problems. (The excitement of the day may already cause this!) Pre-race meal This meal, which is usually breakfast, should be eaten four hours before the start. It should include individual preferences for familiar foods, but the following is recommended as a meal that is non-gas forming and well absorbed, leaving little to enter the bowel. Sample menu Stewed fruit Rice bubbles and non-fat milk White toast and honey (no butter)

Fruit juice Coffee and non-fat milk. During the next three hours, diluted juice (1:3) and water should be consumed. Sugar Under normal circumstances our gut will tolerate a 5 per cent sugar solution (equal to fruit juice diluted 1:1 with water), but during the stress of the marathon a 2.5 per cent solution is considered best to prevent the gastrointestinal problems. This is % teaspoon of glucose for every 100 millilitres ( l, z a cup) of water or pure unsweetened fruit juice diluted 1:3. Sugar taken just before and during exercise can ensure that there is more carbohydrate in the fuel mixture over four hours or more. This extends the period of intensive effort. On the other hand, an excess of sugar an hour before the marathon is not advisable (such as soft

drinks, ice-creams, lollies, honev and athletic drinks). Some people are susceptible to a surge of insulin into their bloodstream which can lower blood sugar, necessitating an early use of glycogen, promoting early fatigue. (But same glucose solution already suggested is suitable.) One hour before Researchers have shown two cups of coffee cause the release of fatty acids into the blood which the muscles will preferentially use at the start of the race, conserving the glycogen. Caution: An excess of coffee can cause dehydration on a hot day or may cause diarrhoea, anxiety, or sleepIfssnp'vS A further 200 to 500 millilitres of the suggested glucose solution or diluted fruit juice should also be consumed in the last hour before the race. Lack of urine indicates a need to drink more.) During the race Fluid replacement is the most important factor of diet during marathon running. After training fluid replacement is probably the next most important factor in successful marathon running. We can absorb only 1000 millilitres of liquid from our intestines each hour, so there is little point in having more than 400 to 500 millilitres each half-hour. Runners with less training are more sensitive to heat and may well require this amount, whereas fast runners will suffice with 150 to 250 millilitres every 20 minutes on a cool day.

It is too dangerous to wait until feeling thirsty. Drinking must start at the first feed station, and continue at all feed stations. Women have less body surface from which to lose fluid so that 150 millilitres at each feed station is probably sufficient. Drinks should be' cold. Because of varying individual needs race organisers allow runners to have their own drinks. Commercial athletic drinks are generally highly concentrated, and require a lot of dilution. Salt tablets and salt solutions are not necessary unless there are extremes of heat, and • should only be taken on the advice of a physician. Obviously some athletes can run without these precautions, but scientific evidence is helpful for those who want to try for optimal performance. A supply of carbohydrate before the event as stores derived from a high carbohydrate diet and rest during the event (as 5 grams glucose or 1 glucose tablet per 100 millilitres) preserves the runner’s energy resources during the endurance event of the marathon.