Tulis a continuation for this paragraph - Thijs debut di panggung internasional salila 2002 European Aquatics Championships
di Berlin. Prestasi utama Van Valkengoed nyaéta meunangkeun medali perunggu dina 200 m breaststroke di European Short Course Swimming Championships 2003 di Dublin, Irlandia. Mimiti bulan éta manéhna geus lolos pikeun Olimpiade Usum Panas 2004 kalayan catetan nasional dina 100 m jeung 200 m breaststroke. Dina Olimpiade, anjeunna dileungitkeun dina semifinal tina 100 m breaststroke, sareng dina panas tina 200 m breaststroke.