Kaarle's junior career in sport was broad but her greatest achievements lay in middle distance as a Track Athlete where she held several Australian titles. Her success in sports and academics at school led to her being a recipient of the Pierre De Coubetin award for fair play and academic achievements as well as which she received a scholarship to University in 2005.
It was in the same year she took up cycling, after first trying Triathlon and eventually ending up on the Track. Just one year later Kaarle won her first Australian title in 2006 and competed for Australia at the Junior World Championships in Belgium, finishing 3rd in the 500m Time Trial and 4th in the Sprint and Keirin.
In 2008 she was awarded an AIS scholarship and also signed her first pro team (Team Toshiba). This was followed by her first World Title in 2009 in the Team Sprint with Anna Meares and in 2010 they retained that title in World Record time and were the first women to break the 33second mark. Kaarle also dominated at the Australian Track Championships in 2010 winning 4 Australian Titles (Sprint, Team Sprint, Keirin, 500m TT)