<prompt> Qedela umusho olandelayo: U-Prieto wazalelwa eSegovia, futhi wenza i-debut yakhe yamazwe ngamazwe e-1983 European Athletics Junior Championships, ehlala endaweni yesihlanu ekuhambeni kwamamitha ayi-10,000. Waba ngowesikhombisa emjahweni wokuhamba ibanga elingamakhilomitha angama-20 ku-1985 IAAF World Race Walking Cup wabe eseqhubeka nokuwina indondo yethusi kulo mcimbi kuma-European Athletics Championships ka-1986. Wazibonakalisa njengomunye wabahamba ngezinyawo abahamba phambili eSpain, waqhudelana eMqhudelwaneni Womhlaba Wonke Wezemidlalo ngo-1987 nango-1991. U-Prieto wanqoba indondo yakhe yesibili yamazwe omhlaba kuma-Universal Summer Universiade ka-1989, lapho athola khona indondo yesiliva ekuhambeni amakhilomitha angama-20 ngemuva kweWalter Arena yase-Italy. Wafika ngo-13 emncintiswaneni  <response>: 1990 European Athletics Championships futhi waqeda indawo eyodwa ngaphansi kwalokho ku-1991 IAAF World Race Walking Cup. 