People can even die running both marathons and half-marathons. In the first 30 years of the London Marathon, 10 competitors died, with eight of those cardiac cases. Sportscardiologists recommend screeningfor many runners.
Jedward are not the only figures said to have completed a marathon without preparation
Death -Running a marathon or half-marathon can be fatal. One of the worst recent death tolls was in the 2005 Great North Run, where four people died. Cardiac arrests are frequently the cause, but hyponatraemia, brought on by drinking too much water, has also been blamed.
Dehydration- the body loses fluid through sweating and breathing. An above average runner doing a three-hour marathon could expect to lose 3-5 kilograms of weight. For every kilogram you lose, you need to drink 1.5 litres of water to replace it. Sweat also contains salt (mainly sodium and potassium) so up your salt intake.
Injury- Knees, calves, shins, ankles, hips and heels are all susceptible to being damaged from constant pounding, while muscles experience micro-damage. Runners need to factor in plenty of post marathon rest time because injuries can also occur after the event.
Cramp- This occurs when fatigue and dehydration cause the muscle to tighten up and become incredibly sore. People have had to pull out of races for cramp before.