At the beginning of his sports career, Leman was an alpine ski racer . From December 2001 he took part in FIS races , from December 2002 in races in the Nor-Am Cup . He later joined the Canadian Ski Association's development team. His best results in the Nor-Am Cup are two fourth places, achieved in March 2008, which was enough for third place in the combined ranking. In the European Cup , Leman achieved eighth place two months earlier. After the 2008/09 season he switched to the freestyle discipline of ski cross.
On January 5, 2009, Leman made his debut in the Freestyle World Cup in St. Johann in Tirol and immediately took eleventh place, which was synonymous with the best result in his first season. In the 2009/10 season he made it into the top 10 three times, and won the bronze medal at the 2010 Winter X Games . He qualified for the Olympic Winter Games in Vancouver , but suffered a day before the race while training a broken leg. Leman also missed almost the entire following season and only returned to the World Cup after a year and a half break. The comeback was successful: at the start of the 2011/12 season, he won the World Cup race in San Candido on December 17th, 2011 . On February 3, 2012, another victory followed in Blue Mountain , which resulted in second place in the Ski Cross World Cup in the final bill. In the 2012/13 World Cup winter two second places were his best results.
In the 2013/14 World Cup season , Leman came third three times. At the 2014 Winter Olympics in Sochi , he made it to the finals, but fell and finally finished fourth. Two more podium places were added in the 2014/15 World Cup season , while at the 2015 World Cup at Kreischberg he just missed the finals and finished fifth. In the 2015/16 World Cup season , he made it onto the podium five times, but without being able to win a race. However, he succeeded in doing this in the ski cross competition of the Winter X Games 2016 . Leman continued to show consistent performance during the 2016/17 World Cup season : after finishing second five times, he won the races in Idre and Blue Mountain towards the end of the season , which was enough for second place in the ski cross discipline.