Reneilt started rowing for Germany as a junior in 2006. He finished second in three U23 World Championship events. In 2010, he was promoted to the senior boat by coach
Ralf Holtmeyer .
Reinelt was part of the team that won the gold medal in the men's eight competition at the 2012 Summer Olympics in London. It was Germany's first gold medal in the event since 1988. He also won gold in the men's eight at the 2010 and 2011 World Championships and the 2013, 2014, 2015, and 2016 European Championships, and silver at the 2013, 2014, and 2015 World Championships. He was also part of a German team that won a record 36 consecutive races. At the 2016 Summer Olympics in Rio de Janeiro, he competed as part of Germany's men's eight team which won the silver medal. The eight rowers were awarded the Silbernes Lorbeerblatt (Silver Laurel Leaf), Germany's highest sports award, for their achievements.
After the 2016 Olympics, Reinelt retired to focus on studying medicine in Bochum. He was one of three rowers from the German 2016 Olympic team who retired after the Games, the others being Andreas Kuffner and Maximilian Munski. In early 2019, Reinelt became doctor of the Germany U23 rowing squad. He had been scheduled to attend their rowing camp in Mequinenza, Spain.