As the Paralympics get ready to start in a London, a form of natural doping called "boosting" has emerged.

It's a gruesome practice in which athletes with spinal injuries intentionally injure themselves in order to gain a competitive advantage.

Here's how it works:

Many quadriplegic athletes suffer from chronically low blood pressure. As a result, they don't get the automatic increase in heart rate and blood pressure that able-bodied people get from physical activity, spinal injury expert Dr. Andrei Krassioukov told Txhnologist. So, basically, they have less energy.

In order to trick the body into raising its blood pressure, an athlete will injure his or her lower body in an number of awful ways. According to the BBC, athletes have broken their toes with hammers, electroshocked their testicles, and blocked their catheters for days in order to make the bladder swell.

The athletes don't feel the pain (because they injure body parts below their spinal injuries), but their bodies automatically go into distress and kick into overdrive. This simulates the automatic boost able-bodied people get from physical activity, and gives the athlete an advantage on the field of play.

The practice is extremely dangerous though. Quadriplegic climber Brad Zdanivsky told the BBC, "You are getting a blood pressure spike that could quite easily blow a vessel behind your eye or cause a stroke in your brain."

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So why do they do it?

According to Krassioukov, it all has to do with the fact that Paralympic athletes don't compete on an even playing field.

Right now, athletes compete against each other based on which of their body parts still work.

So, for example, all quadriplegics compete against each other even though some of these athletes have blood-pressure issues while others don't. Krassioukov says athletes "boost" so they can make up for that inherent disadvantage.

Until these athletes are reclassified and the playing even is leveled, he doesn't think boosting will go away.

The BBC reports that 17 percent of athletes polled at the Beijing Games said they had tried boosting before. Krassioukov believes that number could be as high as 30 percent.

The International Paralympics Committee has banned boosting. It tests athletes before games and bans any competitor with an artificially high blood pressure.