Bryan Kirkland could always spot a booster. Sweaty arms, shaky legs and "chicken skin" were telltale signs of the dangerous practice, banned from the Paralympics for its performance-enhancing effects.
"All I could do was shake my head," said Kirkland, 41, a Paralympic gold medalist from Leeds, Ala. "It's so dangerous, and for what: so you can win a race?"
Like blood doping, boosting increases the amount of oxygenated blood circulating in the body. But instead of using blood transfusions and erythropoietin injections, boosters break their toes, block their catheters and crush their scrotums.
"This practice is very unique to individuals with high-level spinal cord injuries," said Dr. Yagesh Bhambhani, professor of rehabilitation medicine at the University of Alberta in Edmonton, Canada, explaining how a spinal cord injury blocks pain signals from the body to the brain. "An able-bodied person would not be able to do this."
Boosting uses self-inflicted injuries to trigger autonomic dysreflexia, a condition that's considered a medical emergency when it happens by accident. Although boosters can't feel the pain, it activates the sympathetic nervous system, causing risky rises in blood pressure.
"If you raise your blood pressure, your heart theoretically pumps more blood. If your heart pumps more blood, you get more oxygen. And if you get more oxygen, your performance is improved," said Bhambhani, author of a 1994 study that found boosting could improve wheelchair race times by nearly 10 percent.
But boosting is dangerous. It was banned at the Paralympics in 2004, "not only because it's performance enhancing, but also because it's a huge health risk," according to Craig Spence of the International Paralympic Committee. "We want athletes to play by rules, play fair, and not risk a heart attack or a stroke for a medal."
Spence said athletes are screened for high blood pressure before certain events, like wheelchair racing. But because autonomic dysreflexia can happen unintentionally -- if an athlete is strapped into a chair too tightly, for example -- boosting is difficult to detect.
"If an athlete generally has high blood pressure and has a medical certificate to prove it, we will allow those athletes to compete. But if an athlete is really tense and doesn't have a certificate -- even it's from autonomic dysreflexia -- then they're banned from competing on the grounds it could lead to a heart attack or a stroke," said Spence.
Kirkland, a quadriplegic wheelchair racer and rugby player, said he has never boosted. But he has experienced autonomic dysreflexia by accident.
"My bladder was full I couldn't get it to empty out," he said, recalling the panic of the sudden surge in blood pressure. "My stomach got really spastic, I got goose bumps -- we call it chicken skin -- and my head started to hurt. I could feel my heart beating in my head."
Kirkland broke his neck in a motocross accident when he was 20 years old, and quickly learned the signs of autonomic dysreflexia, which can be triggered by something as innocent as an ingrown toenail.
"They call it the rookie years of being a person with a disability," he said.