Toomey began participating in CrossFit in 2013 after primarily being a runner. She learned the basics of weightlifting through her CrossFit classes. She was approached by the weightlifting coach Miles Wydall after he saw her lift her then-personal best 80 kg (180 lb) clean and jerk in a CrossFit competition. He encouraged Toomey, and her husband, to try to get to the Rio Olympics representing Australia, which she qualified for after just 18 months of serious weightlifting training.

She is an established CrossFit Games competitor, and has finished second overall in both the 2015 and 2016 CrossFit Games. Because she participated in the Olympics less than a month after finishing the 2016 CrossFit Games, she garnered some criticism for not being a focused sport-specific athlete like many she qualified over. Many CrossFit writers defended Toomey’s performance, citing she did as well as could be expected from any competitor within the Australian Weightlifting Federation, a nation that only qualified to bring two weightlifting athletes to Rio (compared to an exceptional weightlifting federation, such as China, that qualified to bring ten athletes). She later won first place in the 2017, 2018, 2019 and 2020 CrossFit Games, becoming the first woman ever to win four consecutive titles.

At the 2018 Commonwealth Games, she won gold in the 58 kg (128 lb) event with a combined total of 201 kg (443 lb).

Toomey used to own a gym with her husband, Shane Orr, who is also her coach. They sold it in early 2019 to move to Cookeville, Tennessee, to train at Rich Froning’s gym CrossFit Mayhem. Multiple CrossFit Games male champion, Mat Fraser, then joined them in Cookeville and Shane coached both of them in preparation for the 2019 CrossFit Games.