"It's pretty amazing, this is my third Paralympics," she said.
Southorn competed in Athens in 2004 and in Beijing four years later where she managed a top eight finish in three races.
This year, she will compete in five races but her speciality is in the 3000m in the velodrome.
A 500m time trial, a team sprint and two road races make up her other races.
"Most of my preparations are done at home, on the road, and I have a full gymnasium equipment in my garage and I train with help from my coach Jono Hailstone."
She thanked the Waipu community for their support as she starts her London preparations with four training camps in Invercargill.
On where to after London, she said: "I'll keep competing and see where it takes me ... who knows. I am getting faster as I get older."
Southorn had only ever competed in able-bodied competitions until August 2002.
Northland's next best hope of making it into the NZ Paralympics squad is swimmer Cameron Leslie who won gold in Beijing in 2008.
The Paralympics swimming squad will be selected on June 1.
The Paralympic Games will run from August 29 to September 9. New Zealand has won 180 Paralympic medals.
