WHO, WHAT, WHY?
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A man is on his 13th day riding a rollercoaster. What physical effect might this have?
Rodriguez in action
Nine days, or 221 hours, may sound like a long time to spend strapped in a seat experiencing breakneck speeds.
But Richard Rodriguez has hardly got going. On Monday the American broke the world record of nine days and 12 hours for the longest rollercoaster marathon - subject to verification - but intends to stay riding at Blackpool's Pleasure Beach until Monday.
He knows he can do it, having spent three months on Blackpool's Big Dipper in 2000, before Guinness Book of Records changed the rules governing rollercoaster rides.
So what does continuous dipping and loop-the-looping do to the body?
"Being on a rollercoaster this long could cause sleep deprivation, which in turn would lead to tiredness and lethargy, and could affect the immune system, making him more susceptible to coughs and colds," says Dr Graham Archard, vice-chair of the Royal College of General Practitioners.
May cause sleep deprivation, neck injuries, permanent disorientation and weaken immune system
But Rodriguez spent three months on a rollercoaster in 2000 with no apparent ill-effects
"Unless he's wearing a neck brace, it could cause neck problems that may stay with him for life, and aches and pains in his joints from hanging on too tightly.
"He could also develop a rare condition called 'mal de debarquement syndrome', which leaves people permanently off-balance, possibly for life."
Headway, a charity for people with brain injuries, says there are associated dangers.
"The risk of head or brain injury from amusement park rides is very low but staying on a rollercoaster ride for over two weeks is definitely not advisable," says a spokeswoman.
"Despite the hardness of the human skull, the brain is vulnerable and can be easily damaged, resulting in multiple effects which can stay with you for life."
But Andy Hine, chairman of the Roller Coaster Club of Great Britain, says the main concern will be sand.
"I joined him for a night when he did it last time and the main problem is that because it's right on the seafront at Blackpool, you're getting the wind - and in the wind there are particles of sand and he's doing 60, 70, 80mph with sand hitting him in the face. Last time he had very rosy cheeks at the end; he looked like he needed a good moisturiser."
Mr Hine himself spent 18 hours on a rollercoaster in Ohio in 1992 to raise money for charity, and the main problem for him was boredom.
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"After a while I felt like I shouldn't be sitting there, I had other things to do. It was fun but I wouldn't be rushing back."
He had the chance to hop out of his seat for a few minutes every time the ride returned to the station, so he could stretch his legs, drink water or eat a hot dog. That prevented him getting dizzy, but Mr Hine, who has 35,000 rides to his name, thinks rollercoaster novices would start to feel nausea and headaches after an hour.
Advances in engineering technology mean that some rides in the UK, such as Stealth in Thorpe Park, are capable of propelling people from 0 to 80mph in under two seconds.
While experiencing the twists and turns of modern rides - usually made of steel rather than the traditional wood - their bodies are momentarily put under the same G-force pressure endured by fighter pilots and space shuttle crews.
G-force on UK rides reaches 5g
Enthusiasts say negative G-force is more fun
This gives feeling of weightlessness
Raising hands at top of climb can exaggerate this feeling
Source: Rollercoaster Club of GB
Major injuries from rollercoaster riding are very rare, but people with heart conditions or neck complaints are usually warned not to take part. And height restrictions are in place to stop people falling out.
The Health and Safety Executive says there have been 40 confirmed incidents occurring at fairs and amusement parks in the North West since 2001, resulting in 22 major injuries. Most were because people ignored safety instructions.
There have been links made between rides and internal injuries. Cardiologists in Germany say the thrill of the ride can spark irregular beats in those with heart disease and put them at risk of a heart attack.
US researchers have examined cases where people claim to have suffered blood clots on the brain, but their report only concludes that more study is needed. However a doctor in Japan has warned about the hidden dangers of rollercoaster riding after a patient suffered blood clots on the brain.
A more conclusive link between injuries and rollercoaster riding led to a Lincolnshire amusement park redesigning its ride after customers complained of "nipple burn" from too-tight straps.
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