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Autologous platelet-rich plasma (PRP) was prepared using the RegenKit THT system (RegenLab SA, Le Mont-sur-Lausanne, Switzerland) following the manufacturer's instructions. Medical technicians, who had been well-trained by the manufacturer, were responsible for the process of PRP preparation. For each patient, 8-10 mL of venous blood was drawn and collected to the commercial RegnLab THT tube, which contained 1 mL sodium citrate. After single centrifugation at 3400 revolutions per minute (rpm) for 8 minutes, 4-5 mL of PRP was yielded with leukocytes maintained at physiological levels and red blood cells depleted. Then, the blood components were separated, with the platelet pellet resting on the separating gel. PRP for later application was obtained by re-suspending the platelet pellet in the plasma supernatant by gently inverting the unopened RegenKit THT tube 5 to 10 times.

Doping substances in urine, mainly metabolites of anabolic androgenic steroids (AAS), were quantified, including testosterone (17β-hydroxyandrost-4-en-3-one), epitestosterone (17α- hydroxy-4-androsten-3-one), androsterone (4-androsten-3,17-dione), etiocholanolone (3α-hydroxy-5β-androstan-17-one), DHEA (dehydroepiandrosterone), dihydroandrosterone (5α- androstane-3α,17β-diol), and etiocholane-3α,17β-diol (5β -androstane-3α,17β-diol). Each urine sample (6 mL) was mixed with 50 μL standard solution and 1 mL phosphate buffer, and the mixture was heated for 60 min at 50°C. After cooling at room temperature, liquid-liquid extraction was performed, and phase separation was achieved. The organic extract was evaporated to dryness, and the dried residue was further derivatized with 50 μL of MSTFA solution for 30 min at 60°C. Finally, the sample was subjected to gas chromatographic analysis and mass spectrometric analysis for quantification of doping substances of interest.