In 2019 Arnold lost her World Record to New Zealand F46 Para Javelin Thrower Holly Robinson with the first 45m+ throw in history.

[4] She joined Cleethorpes Athletic Club and began her career under the watchful eye of Olympic Javelin Thrower, Shelley Holroyd.

[6] In 2008, at the age of 14, she was selected to represent Great Britain at the Summer Paralympic Games in Beijing, finishing 11th in the women's F42–46 javelin.

[6] The next year she won her first significant medals when she competed in the 2009 IWAS World Junior Championships in Switzerland, winning silver in the F46 discus and bronze in the F46 javelin.

[4] The year 2011 saw Arnold step up to the senior level representing Britain at the IPC Athletics World Championships in New Zealand; she finished third in the F46 javelin, taking the bronze medal.

[4] Her personal best at F46 javelin was recorded at 35.88m in June 2012 at the Welsh Championships in Cardiff, ranking her as the world number two in her event going into the 2012 Paralympics.

In 2014, Arnold was preparing for the buildup to the IPC Athletics European Championships in Swansea, hoping to improve on the silver medal she won in Stadskanaal two years prior.

[9] In September 2016, Arnold won the gold medal at the 2016 Summer Paralympics in Rio de Janeiro with a world record throw of 43.01 metres.