Briton Sara Campbell is on a mission to stretch the limits of the human body -- diving down into the murky ocean depths for minutes at a time, on a single gulp of air.(AFP) -
Briton Sara Campbell is on a mission to stretch the limits of the human body - diving down into the murky ocean depths for minutes at a time, on a single gulp of air.
Extreme depth freedivers swim down and back as far as possible, while coping with pressure that crushes their lungs to the size of a lemon and would wreck their eardrums if they were not careful.
And the record-breaking Briton admitted it is tough. "Each dive is a phenomenal physical and mental challenge," the 37-year-old told AFP. "Your body goes through very extreme changes.
"Your heart rate drops, all the blood comes to the centre of your body, and then that blood starts to fill the lung tissues so that the air spaces can contract even more.
"For every 10 metres (yards) that you descend, the pressure doubles, so that means your lungs halve in size. So down at 90 metres, 100 metres, they're about a ninth, tenth of the size."
Campbell, who shot from freediving beginner to world record holder within months, is out to break the record again and crack the 100-metre barrier in 2010.
She earned a silver medal at the World Championships in the Bahamas earlier this month with an "easy" dive of 92 metres. That has fired her up to reclaim the world records from her only rival, Russia's Natalia Molchanova, in 2010.
One metre 50 centimetres tall (just under five feet), Campbell's extraordinary ability has rocked the sport of freediving.
Some physiologists believe the yoga trainer from Burnham-on-Crouch in southeast England is a "natural" freediver, able to hit significant depths with little training.
Campbell believes she was born to do freediving, having a strong mammalian diving reflex, which helps mammals optimise their oxygen underwater. Through evolution, dolphins, for example, have a far stronger reflex than humans.
"It probably means I'm a little bit less evolved as a human being, I retain more of the fish gene and have less of the human gene!" she said.
Four years ago, fed up with the London rat race, Campbell moved to Dahab, a laid-back diving resort on Egypt's Red Sea coast, to teach yoga. One of her students recommended she try freediving, given her breathing control skills.
Tired of chasing targets, Campbell resisted for a year but gave it a go in April 2006.
Hepatitis A stopped her progress after six weeks but she began training again in April 2007 and in October that year, set world records in three different disciplines within 48 hours and then claimed a world championships gold medal.
In the blue riband constant weight discipline, freedivers, using flippers, take a weight down with them to speed up the descent but have to bring it back.
Campbell's personal best is 96 metres, a world record achieved in April in three minutes and 36 seconds under water.
She has dived 100 metres twice, but blacked out within a minute on the surface, invalidating the attempts.
Her rival Molchanova broke the 100-metre barrier in September, reaching 101 metres.
No-one else comes close to challenging the pair.
"She and I are now playing ping-pong with the world records," Campbell said.
"It's like the Cold War! There's definite rivalry. It's the two of us battling it out at the top. We'll see what happens next year but having seen how strong my silver medal dive was I'm really fired up.
"I'm certainly not going to sit back and let Natalia push her dives very much deeper."
Campbell enjoys stretching man's boundaries.
"Not so long ago, medical science said beyond 50 metres it is not possible for the human being to survive.
"The exciting thing is you do a dive, you don't know if you can make it but when you do, a door opens and you realise that actually you can go a bit further," she added.
"Human beings have almost limitless potential and a lot of that is governed by the mind. If you believe something, you can achieve it."