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Friday, 16 April, 1999, 13:46 GMT
Marathons - how to survive one
Every year the London Marathon throws up grim stories of runners suffering heart attacks during the race. However, proper preparation should mean that even the most inexperienced athlete can complete the 26 miles 385 yards without suffering serious injury.
The importance of diet
A top priority for anybody planning to run a marathon is to stock up on carbohydrates.
The main source of energy during a race comes from burning up the body's store of glycogen which comes from carbohydrates such as pasta, bread and potatoes.
Burning glycogen produces quick energy, unlike burning up fat, which produces energy at a rate far too slow to be useful during a long road race.
John Brewer, head of sports science at the Lilleshall Sports Injury and Human Performance Centre and a veteran of five London Marathons, says that eating more carbohydrate than usual is vital for at least a week before a race.
"Normally glycogen stores will last for one-and-a-half to two hours of exercise," he said.
"If you do not boost stores beforehand, there is a good chance you will get to 18-20 miles and run out of energy - what is known by athletes as hitting the wall."
Mr Brewer said the best way to top up glycogen levels was to eat 50% more carbohydrates than usual with each meal for the week before the race.
On the morning of a 9.30am race he suggested a 6am breakfast of cereal or toast with jam or honey.
Fluids are vital
It is important that marathon runners ensure that their fluid levels do not become too depleted during a race.
This becomes even more vital on warm days, when the body will sweat more to keep cool.
Mr Brewer said the best way to maintain fluid levels was to drink isotonic sports drinks during the race. These drinks also provided easily digestible carbohydrates to boost energy.
"If it is warm it is important not to wait until eight or nine miles before starting to drink," he said.
"You should start taking on fluids as soon as possible from the first drink station. Once you start to feel thirsty it is too late."
What happens if you get dehydrated?
Towards the end of a marathon it is common to see athletes staggering around, seemingly having lost control of their own bodies.
It is likely in these cases that they are suffering from serious dehydration.
When the body becomes dehydrated it suffers from a condition known as hyperthermia, or over heating.
"The body begins to lose the ability to supply blood where it is most needed," said Mr Brewer.
"A lot of blood is diverted to the skin in an attempt to cool down, and as a result the brain is deprived of oxygen.
"When this happens the body's safety mechanism cuts in and tries to stop the exercise and get the brain down to the level of the rest of the body as soon as possible so that blood can pour back to where it is required."
it is also possible that an athlete will simply run out of steam when glycogen supplies are exhausted.
Are injuries likely?
The vast majority of marathon injuries are low level skin abrasions, caused by areas such as the armpits and the groin rubbing together.
Joggers nipple is also a problem in women. The best way to avoid chaffng of this sort is to use vaseline.
Muscle strains are unlikely as most people who run a marathon do not overstretch.
It is important to make sure that running shoes are well broken in before taking part in a long distance race.
Hard shoes may rub into the achille's tendon at the back of the heel.
What is the risk of heart trouble?
In almost every marathon that includes part-time runners, somebody will suffer from a heart attack.
However, Mr Brewer points out that in any population of 30,000 people it is likely that during a three to four hour period somebody will have problems with their heart.
The best way to avoid problems is to ensure that you are well prepared for the race in advance.
This means sticking to a regular programme of running for four to six months before a race, gradually building up distance over time.
It is advisable to complete two or three long distance runs of at least 18 miles before attempting a marathon.
Keep up a steady pace
The best way to run a marathon is to keep up a steady pace, and not to sprint off from the start.
Experienced runners know that they should not push themselves to the absolute limit early in a race.
If the body is pushed to extremes it will start to metabolise glycogen supplies without using oxygen.
This leads to the build up of lactic acid in the muscles which will make the runner heavy legged and force them to slow down.
What about after the race?
It is sensible to try to replenish carbohydrate supplies as soon as possible after a marathon to aid the speed of recovery.
While muscle aches are inevitable after running more than 26 miles, it should be possible to get energy levels back to normal within one or two days.
However, if carbohydrate levels are not replenished within a few hours of a race, tiredness may linger for the best part of a week.
Links to other Medical notes stories are at the foot of the page.
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