London Marathon Q&A

Thousands of runners will be passing Big Ben this year

BBC Sport gave you the chance to quiz the experts at the English Institute of Sport on running the London Marathon.

Nutritionist Rebecca Stevenson, physiologist Dr Craig Williams and Dr Richard Budgett provide the answers.

Q: While training, I have been running 15 miles without drinking any water during the run. Is it a good idea to get used to running on just the fluid you take before you go out? Malcolm, Inverness, 20

A: The general guideline for exercise that lasts more than an hour is to drink 150-250ml every 15 minutes to offset possible fluid losses.

The emphasis is on drinking smaller volumes more frequently to minimise stomach discomfort.

Getting the right balance of water in the body is crucial

However, when you are undertaking prolonged exercise such as a marathon, it is important you are careful about the amount of fluid drunk.

For example, a runner would need to drink between 2-4 litres of fluid for an average marathon.

Knowing how much liquid you sweat per hour is the best way to avoid both dehydration and over hydration.

So for a four-hour marathon, a 500ml per hour sweat rate would need two litres, whereas a 1000ml per hour sweat rate would need four litres.

Those taking a long time to complete the marathon should not drink large amounts frequently to avoid over hydration.

Use sports drinks which contain sodium to prevent diluting your body's salt levels.

Water is available at practically every mile point at the London Marathon, but this doesn't mean you need to take a drink every mile or indeed drink the whole bottle!

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Q: What is the best food and drink to have after a run? Rikesh Mistry, Rugby, 24

A: Carbohydrate is the key nutrient for energy supply. So make carbohydrate-rich foods the focus of your training diet.

Before the race:
Although you need to allow 2-4 hours after a large meal before exercising, a high carbohydrate snack within 30-60 minutes before training is generally found to be beneficial, providing enough carbohydrate - at least 50g - is eaten.

Pasta is the ideal pre-marathon food

Eating carbohydrates just before exercise not only improves performance, but also helps maintain blood sugar levels and prevents the feeling of light-headedness.

During the race:
During intense exercise that lasts for longer than an hour, it is advisable to consume 30-60g of carbohydrate per hour because it generally improves performance.

This intake is best achieved by eating every 10-30 minutes (depending on what is practical and allowed by the sporting event) and should be continued throughout the event so that it provides a steady flow of glucose into the bloodstream.

After the race:
It's also useful to take a carbohydrate and protein snack within 30 minutes following exercise to help restore muscle and liver carbohydrate stores. Try to eat a carbohydrate-rich meal within two hours.

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Q: Which foods and drinks are best to achieve the maximum replenishment of the body's essential stores? Kevin Tulloch, Aberdeen, 42

Orange juice provides the perfect energy boost

A: Eating carbohydrates immediately after strenuous exercise will not only help the muscles start effective recovery, but it also takes advantage of the enhanced rate of glycogen storage at this time.

Start your carbohydrate intake as soon as is possible. It might be easier to do so by taking in a series of small snacks, as opposed to a large meal.

It is recommended that in the immediate recovery phase - within the first four hours after exercise - about 1-1.2g of carbohydrate per kilogram of body weight is eaten in each hour.

The following snacks provide approximately 50g of carbohydrate:

500ml isotonic sports drink and pot of low fat custard

200ml orange juice and two slices currant bread

5g jelly sweets and 150ml orange juice

150ml carrot juice, three rye crispbreads with cottage cheese to taste plus 100g fresh pineapple and a small apple

100g grapes, two fig rolls and 150ml orange juice

Lean ham and salad sandwich (two slices brown bread) and 200ml apple juice

175g baked potato with filling

200g drinking yoghurt and a fruit scone

One crumpet and a teaspoon of jam plus 500ml isotonic sports drink

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Q: With so much diet advice and so many nutritional supplements out there in the market place, what do the experts recommend for the diet and nutritional needs for the long distance runner?

I ask because I find myself very tired at work, in between training sessions and longing for that morning coffee! Dominic Prowse, Wellington, 31

A: Long steady runs and shorter high-intensity runs will drain your glycogen reserves.

Long-term muscle depletion can cause damage and impair the muscles' ability to store glycogen.

High-protein sandwiches are good recovery foods

Refuelling with carbohydrates following such training will prevent this.

Carbohydrates taken immediately after training help to restore glycogen stores most effectively, as this is the time that the body is most efficient at storing carbohydrate.

In the first 30 minutes, carbohydrates will help to start muscle and glycogen resynthesis.

In response to carbohydrates, the hormone insulin is released into the bloodstream and this will help the body to repair and regenerate damaged tissues.

Studies show that a small amount of protein taken with carbohydrate will help this recovery process.

Try taking 1-1.2g carbohydrate per kilogram of body weight, plus 10-20g protein after training.

Try low-fat milkshake drinks, or a sports recovery drink that contains adequate protein, or a sport drink and a sandwich heavy on protein.

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Q: What you think about taking supplements like creatine? Do they work? If so, how often should I take them and are there any downsides? Paul George, Birmingham, 18

A: Most athletes can get adequate protein from dietary sources without using protein supplements.

The best advice is to ensure your diet contains good quality protein (lean meat, fish or eggs) or if vegetarian ensure good balance of vegetarian sources (beans, lentils, nuts, seeds).

Fish is an ideal source of protein

If trying to build lean body mass you can increase your total calorie intake (500kcal per day) together with resistance training.

Aim to take in 1.2-1.4g of protein per kilogram of body weight per day. Ensure that your post-recovery snack contains 10-20g protein.

There is evidence that creatine supplementation can increase the amount of creatine phosphate in the muscles and can improve performance in strength and power events.

It has been associated with rapid weight gain, which can be an advantage or disadvantage to some sports.

Not all athletes benefit from taking creatine. A loading dose of 20g per day for 3-5 days or a dose of 3g per day over 30 days will have the same effect and 2g per day will maintain levels.

Short-term effects of taking creatine are unclear and long-term effects are not known.

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Q: I run regular half marathons and my best time is one hour 33 minutes.

I find up to 10 miles I'm OK and running 1hr 29 pace but after 10 miles I have no energy and nothing left in the tank and my time suffers.

Could you please give me some advice on how to improve my stamina and improve my times. Andy, Bradford

A: Assuming you're not expecting any advice to have an impact before Sunday, your stamina can definitely be improved.

One hour 33 minutes is a good half marathon time and you're obviously training, but without knowing your training history and your fuelling/hydration strategy during the race, it is difficult to pinpoint the problem.

Ice baths: Only to be endured by the bravest...

Look at your pre-race fuel intake and what you take on board during the race.

Pacing is key during the race.

You've done all the training, you're well rested and excited and motivated by the crowd - be careful not to start too fast.

Setting out at too high a pace will result in you running out of carbohydrate stores and "hitting the wall" prematurely.

It is worth considering what you will do after the race. Although the efficacy of ice baths and massage is equivocal, getting out for short, light runs in the days after may help speed your recovery.

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Q: This will be my first marathon. What exercise should I be doing in these final few days to fully prepare for Sunday? Rob Ogden, London, 26

A: You should be resting as much as possible.

This is known as tapering and enables your body to adapt from the training stimulus.

However, some people do like to continue some form of training up until the big day and as long as you don't go mad, a light jog will be fine.

The Wall: Hit by almost all marathon runners

If you haven't run a marathon before then I'm sure you've heard lots of stories about hitting the wall.

Well, stop worrying as there is no need for you to hit that wall. All it needs is a little thought and preparation.

Hitting the wall is simply the terminology runners use for fatigue.

You become sluggish, reaction time slows down, co-ordination and balance start to go, concentration dwindles and you feel light-headed - these are all signs of fatigue.

The main cause of fatigue is due to running out of those vital carbohydrate fuel stores - although dehydration alone can also result in fatigue.

Therefore you need to start the race not only well hydrated, but also with a full tank of carbohydrate fuel.