Purpose

Platelet-Rich Plasma (PRP) has been banned in competitive athletes because some people think it may enhance athletic performance. However, there is very little published research to support or undermine this point of view. The purposes of this study are: (1) To assess the effects of local platelet-rich plasma (PRP) therapy on systemic levels of growth factors with suspected or known performance-enhancing effects; and (2) To understand whether the effect of PRP therapy on these growth factors differs between intramuscular and intratendinous PRP injections. This research study is looking for 40 people who are receiving platelet-rich plasma therapy for a tendon or muscle injury. The study involves collecting seven blood samples (2 teaspoons each) from each patient, before and after the PRP treatment. Blood samples may be donated at any location of the patient's choosing, and participants will be paid for their time.