Kostoglod did not take up canoeing until the age of fourteen, at the suggestion of family friend and double world champion Vladimir Ladosha.

By 18 he was senior national champion and competing at the Barcelona Olympics, He was disappointed to finish tenth in the C-1 1000 m but has since admitted that as a youngster he was relying on his natural strength to make up for his lack of technique.

In 1998, with Maxim Opalev now representing Russia in the C-1 events, Kostoglod teamed up with Aleksandr Kovalyov for the C-2.

Three medals he won at the 2003 championships in Gainesville were stripped from Kostoglod when his teammate Sergey Ulegin tested positive for doping.

Together they became both European and world champions, finishing over a second ahead of their nearest challengers, the German pairing of Nuck and Holtz, in both finals.