Athletes have cheated by over-representing impairment to have a competitive advantage, and the use of performance-enhancing drugs. German skier Thomas Oelsner became the first Winter Paralympian to test positive for steroids in 2002. He had won two gold medals in the alpine events but was stripped of his medals. One concern now facing Paralympic officials is the technique of boosting blood pressure, known as autonomic dysreflexia. The increase in blood pressure can improve performance by 15% and is most effective in the endurance sports such as cross-country skiing. To increase blood pressure athletes will deliberately cause trauma to limbs below a spinal injury. This trauma can include breaking bones, strapping extremities in too tightly and using high-pressured compression stockings. The injury is painless to the athlete but affects the body and impacts the athlete's blood pressure, as can techniques like allowing the bladder to overfill.