Sonja first started contact sports with Judo for a short while as a child. She then took up Goju-Ryu Karate at the Daigaku Karate Kai Club at the University of Westminster in 1995, where she has been training ever since.

"Since I started to train in Goju-Ryu Karate I have been fascinated with the completeness and power of this dynamic fighting system."

Sonja achieved the rank of Shodan Black Belt in June 2001 at Daigaku Karate Kai's annual Summer Training Camp. She earned her Nidan grade in 2007 after successfully completing her grading and 30 Man Kumite.