More and more couples are willing to run a gamut of risks to spice up their sex lives, writes Celine McGillicuddy

Lisa had just discovered that her boyfriend Keith (not their real names), who she describes as "a really down-to-earth normal, guy", enjoys extreme sexual experiences.

"We were seeing each other for about two months and had slept together a few times," recalls the 25-year-old.

"Everything was really great. Then the last time we were in bed we were drunk, and things got really heated.

"Next thing I knew he started choking me, putting real force on my neck. I was terrified and kicked him, then he stopped straight away and was saying he was so sorry." She goes on: "He thought I was really into it and was enjoying it but I was really upset at the time."
The incident, while initially terrifying for Lisa, has not divided their relationship. "He did make a mistake not telling me that he was into choking like that, but he didn't know how to explain. Now that he has and it's out in the open I have actually really got into it and we are very experimental."

From whips to choking, asphyxiation to spanking, cutting to fake enforcement, the pursuit of extreme sexual highs is not just something that happens in a dark subsection of society. Lisa and Keith are an average couple who have discovered that they are united in their desire to push themselves sexually to achieve a more intense sensation.

"It's like you're on another level, like letting yourself go and everything feels very real."

Chasing the rush or the ultimate sexual high is for many connected with the quest for experiencing a form of "deeper reality".

Amy (not her real name), described to me how she enjoys "fake enforcement" with her boyfriend. "We pretend that I don't want to have sex and then he forces me to. It's fantasy, but it's edgy -we're not deviants, that's just what excites us," says the 28-year-old.

Women I spoke to are rejecting the concept of conventional, traditional sex. "The idea that women are there to be of service is dead and gone, women are powerful sexually and they are not afraid to express it," said Amy.

Women have undeniably new sexual confidence and many are pushing the sexual boundaries to seek a new thrill.

Angelina Jolie has been remarkably frank on why her sexual appetite led her to using knives during sex. From a young age, she says, she was a very sexual person. She had a bisexual relationship when she was a teenager that involved a ritual of self-mutilation. "I got knives out and had a night where we attacked each other ... it felt so primitive ... so honest ... and then I had to deal with not telling my mother and wearing bandages to high school."

She shared her desire to experience this primitive feeling in several relationships.

"I started having sex with my boyfriend and the sex and the emotions didn't feel enough. In a moment of wanting to feel closer to him, I grabbed a knife and cut him. He cut me back. We had an exchange of something and we were covered in blood, my heart was racing."

Jolie and her former husband Billy Bob Thornton made public their use of knives during sex and famously wore necklaces carrying vials of each other's blood. It is without doubt that we are living in an increasingly overt sexualised society. From children's clothing to high street sex shops to the proliferation of lap-dancing clubs and internet porn, sex is ubiquitous to the point of saturation.

Could it be that the search for extreme sexual thrills is a reflection of the desperate need we have to live up to and beyond today's representations of human sexuality? Girls on the dance floor writhe against one another because that's what is perceived to be sexy these days.

It's no longer unusual for couples to have 'open' relationships or multiple partners. Actress Sienna Miller has stated that monogamy is now a " weird thing, it's over-rated because, let's face it, we're all f****** animals."

The art of having sex in public places, now widely known as 'dogging' is no longer taboo and there is a plethora of websites for those interested in partaking or watching. While consenting adults are within their rights to seek whatever sexual thrills they wish, one has to ask where next for the pursuit of the all-new sexual high? Knife play is an accepted norm in the world of BDSM, bondage, domination and sado masochism, and it now appears to be increasingly practised by some couples straying from the world of mainstream sexuality. According to most sources, rules are that knife play is 75% 'touching, scraping and rubbing' and 25% actual cutting. Knives are heated, frozen and handles can be as erotic as the blades.

Sexual experimenting such as this has become known as 'edge play', with an emphasis in the BDSM community on such interaction being 'safe, sane and consensual'. Breath control involving plastic bags, ligatures, choking or belts are assessed using the acronym RACK - risk aware consensual kink. A " safe word" is used by participants of edge play to inform others that the act should be stopped.

Singer Michael Hutchence was a sexual experimentalist who was said to have fixated on auto erotic asphyxiation - a masturbatory ritual in which choking to the point of unconsciousness heightens the sexual pleasure.

When Hutchence was found dead in his hotel room, he was kneeling on the floor with his arms resting on his legs and a belt hanging on the back of the hotel room door. When Paula Yates was asked if Michael Hutchence had ever "choked, strangled or tied her up in bed", she answered " yeah, he did everything, he's a dangerous boy. He certainly would have done all manner of things just to try it."

Inevitably the codes and concept of edge play are being broken down. Dangerously, the transition from 'play' to violence can be made seamlessly, even unintentionally. In the blur of alcohol and drugs or in a heightened sexual state of mind, the lines of fantasy and reality can become unclear, safe words are cast aside and what is left is raw violence.

Meredith Kercher, the British student murdered in Perugia, Italy, was the innocent victim of such raw, sinister and sexually motivated violence. According to reports, Meredith was allegedly killed for 'kicks' by US student Amanda Knox, her Italian boyfriend and another man. According to the judge's report, she was the innocent victim of three people looking for a " new sensation". Knox, whose nickname was 'Foxy Knoxy', had written a short story about rape on the internet and her boyfriend, by his own online account, said he likes "to try risky things".

Meredith was killed allegedly because she refused to participate in an orgy of extreme sexual experience. When Lisa's boyfriend choked her as they made love what motivated his desire? Why is sex no longer enough? How removed is this playful choking from possible tragedy? For those chasing the ultimate sexual high, it seems love itself is no longer sexy and so sex is no longer loving.