Chromý became Junior World Champion with the Czech team in the relay in Dubbo in 2007, together with Štěpán Kodeda and Jan Beneš. He received a silver medal in 2005. He is a member of the Czech Orienteering Team, and started at the World Orienteering Championships in 2010 (Norway) and 2011 (France). He participated in the European Orienteering Championships in 2010 (Bulgaria) and 2012 (Sweden). He won two bronze medals at the World University Orienteering Championships in Spain in 2012.