Career
Raised in Lengel, Gelderland, he participated in football and long-distance running as a child. He gradually became more interested in running and signed up with Running Team Achterhoek, a local group. He competed in national junior competitions and began to train regularly around 2008.
He placed in the top three in the Dutch junior 800 m race in 2009 and 2010.
Kupers began to make an impact nationally in 2012. He was selected for the 2012 European Athletics Championships and made the semi-finals at the competition – his first senior international event.
Outdoors, he came fifth at the European Team Championships first league race, then sixth at the 2013 European Athletics U23 Championships, where he was also seventh in the 4×400 metres relay. 800 metres outdoor – 1:45:28 minimum (2015)
800 metres indoor – 1:46.55 minimum (2014).