Blood-spinning is a method used by athletes to shorten the time to heal an injury. Small samples of the athlete's blood are spun in a centrifuge to increase the concentration of growth hormones. Calcium and the enzyme thrombin are added, forming a gel that is high in natural growth hormones. The sample is then injected into the wound, which can then heal as much as five times faster.
Using this procedure can fall foul of the World Anti-Doping Agency (WADA) due to possible non-natural elements introduced into the athlete's body. A notable case where this procedure was used is that of NFL player Hines Ward. Following this there have been calls to legalize the procedure as scientists argue that it does not improve performance, only recovery time.