Defoe treatment previously banned
Tottenham's use of platelet-rich plasma (PRP) to treat Jermain Defoe and other injured players is a technique previously used by Tiger Woods and Kobe Bryant, but which was briefly banned by the World Anti-Doping Agency (WADA).
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The therapy has achieved remarkable results in speeding up recovery from injuries and in some cases has led to athletes making a comeback after having retired due to injury.
18. Jermain Defoe
WADA banned PRP injections in 2010 but this ban was removed a year later, although the use of isolated growth factors remain prohibited.
The technique involves a small quantity of blood being extracted from the patient, placed in a centrifuge and spun until it separates into its component parts.
The platelets are then injected back into the patient at the point of injury. The growth factors in platelets are believed to speed up healing, but it remains prohibited to isolate those growth factors and administer them directly.
Spurs boss Andre Villas-Boas revealed the club has been using the treatment since the start of the season.
He said: "We believe a lot in [non-isolated] growth factor treatment and plasma platelet treatments. It is not common but does happen from club to club.
"You take out the blood from any part of the body and spin it around. The plasma comes to the top of the blood and you are able to inject it back into the body and that is the part of the blood that heals injuries. It accelerates the recovery process."
UK Anti-Doping confirmed the treatment was acceptable.
A UKAD statement read: "Platelet-rich plasma (PRP) is an autologous blood product used to treat acute and chronic tendon, ligament and muscle injuries.
"WADA banned intramuscular PRP injections in competitive athletes in 2010 but this was removed in 2011 because of limited evidence for a systemic ergogenic effect of PRP, but the growth factors within PRP remain prohibited."