SINJ, Croatia, June 19 (Reuters) - Croatian siblings and Olympics rowing champions Martin and Valent Sinkovic are chasing a second gold in Tokyo but have made it tougher for themselves by changing discipline. The Sinkovic brothers won the men"s double sculls event at the Rio Olympics in 2016, but for Japan they have changed to sweep rowing, where each holds one oar with both hands. "This is a new, slower discipline and it"s difficult to find a balance," Valent Sinkovic told Reuters from the town of Sinj where they are based while training on Lake Peruca. "This was challenging, especially in the beginning. There was a lot of nervousness but we have survived." His brother Martin said changing disciplines was not common in rowing but that gave them motivation. "It took time though," he acknowledged. As their hotel does not have a gym, one of its offices has been turned into a makeshift gym, so the duo lift weights in a small space next to a wall of documents and folders. The brothers said they are in good shape because they could train normally now coronavirus lockdowns were over. The postponement of the Olympics for one year had even helped. "We have got even more time to practice sweep rowing," Martin laughed.