Ask the Experts - Nutrition

Answers from Andrew Hamilton:

Q. I’m a 33-year old male and am training for Mumbai marathon in India. I do my training in Chennai, where the weather is very humid. During my long runs, I begin to feel very hungry after a couple of hours. I normally eat a peanut butter sandwich half hour before running and drink Gatorade and water for hydration. I drag my body around my long run, but I find it very difficult during the end. I run around 30 miles per week including interval training (6 X 800 with 400m recovery jog). My diet is primarily rice based. What would you recommend to increase my performance?

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With relatively limited information about your training routine and overall diet, it’s hard to be precise about exactly why you’re experiencing fatigue during your longer runs. However, there are 3 possible reasons that spring to mind; insufficient dietary carbohydrate, dehydration and the level of your existing endurance conditioning, of which more than one may be a factor here.

Given that you’re training in a hot and humid environment, hydration is absolutely critical. A good method to calculate your approximate fluid requirement is to weigh yourself immediately before and after your long run, calculate the weight loss in kilos, add 50% and then convert that figure to litres. You won’t be able or need to consume that amount during your run, but you should drink enough fluid to ensure that you don’t lose more than 2% of your body weight by the end of the run. Gatorade is fine to drink, as are other drinks, which also supply the electrolyte minerals and carbohydrate at approximately 6% (60g per litre). Try to drink around a litre an hour divided into small drinks. More recently a new type of carbohydrate drink containing 2 parts of glucose/glucose polymers to 1 part of fructose has appeared on the market; initial indications suggest that these may provide superior carbohydrate and fluid replenishment compared to straightforward glucose/glucose polymer only drinks, so you may want to experiment.

Whatever drinks you use, ample dietary carbohydrate is also critical for long training runs; you should ensure your muscles are fully ‘loaded’ with carbohydrate (glycogen) by eating high carbohydrate snacks and meals immediately after training and consuming a high-carbohydrate diet at all other times (at least 60% of your total calorie intake from carbohydrate foods such as rice, beans, lentils, potatoes and other starchy vegetables, starchy fruits such as bananas and cereals and breads if you eat them). There’s also some evidence that eating a low-glycaemic index (slow energy releasing) carbohydrate snack or small meal about 2-3 hours before training can also prolong endurance, and this is certainly better than a peanut butter sandwich, which supplies a significant amount of its energy from fat – not the best source of pre-training calories for extending endurance!

The final point worth making is that running long distances in hot, humid conditions is very hard work – period! It may be that part of the reason you’re experiencing undue fatigue in the later stages of your long run is that you’ve built up you mileage quite quickly and your body is as yet unaccustomed to covering that kind of distance. This will of course improve in time, but you may benefit by seeking advice from an experienced marathoner/coach to see whether your training program is properly matched to your needs and training background.