But the athlete, from Chapeltown, Leeds, was determined not to let her health problems stop her from reaching Rio in 2016 to compete against the best in the world.
After a medal-strewn junior career, in which she was at one point ranked fourth in the country in the 200m sprint, Miss Cox was rushed to hospital and treated for a suspected stroke.
She recovered and was competing in Loughbrough when she realised something was again terribly wrong last September. She felt strange sensations in her legs and struggled to function the next day.
Miss Cox was diagnosed with MS, a disease of the nervous system, and has since been dealing with the debilitating effects of her relapses such as muscle spasms that can make it hard for her to walk.
Keen to fulfil her potential, Miss Cox, now 24, took up cycling in June and been classified as a C2 disabled rider. She will compete in her first paracycling event at the British Cycling National Track Championships today.
“Rio is pretty high up there as a priority and something I can do and everyone’s quite positive that I will be able to do it,” she said.
“It’s about staying in one piece and, with my health being remitting relapsing MS, there is a chance I can have a relapse so it’s about trying to keep my health stable all the way to Rio.”
Having taken a break from studying physiotherapy in Manchester, the athlete is now devoting her time to training and is more determined than ever to represented Team GB at the Paralympics.
A natural talent on the track, Miss Cox was a member of Leeds City Athletics Club before joining Sale Harriers – a famed Mancunian club that has churned out talents including Darren Campbell, Michelle Probert and Diane Modahl over the years.
But since her diagnosis she has had to adapt her life around her MS, a condition which causes damage to the coating of nerve fibres that can lead to symptoms such as fatigue, dizziness, balance and vision issues.
Miss Cox explained: “I can’t train as intensely or do as much. I initially tried to get back and act as if it was the same old me but realised I can’t do it.
“It’s being more thoughtful and getting more quality than quantity.”
By managing her symptoms, changing her diet and focussing her training regime, she has kept her MS under control and had a successful season. She won three gold medals at the CPISRA World Games in August.
Miss Cox took up cycling in June and impressed British Cycling paracycling coaches, prompting her entry into today’s competition as she also prepares for IPC Athletics World Championships in Doha next month as a sprinter.
She will compete in the T37 100m, 200m and 4x100m events before returning home to Leeds and taking a final decision on which sport to concentrate on in Rio in 2016.
“Cycling’s not as uncomfortable for me and in terms of keeping me healthy it’s working quite well,” she said.
“I just want to compete and be the best I can be.”
The Leeds athlete has now launched a £5,000 fundraising campaign to pay for equipment and travel as she focuses on achieving her Rio ambitions over the next year.
Visit gofundme.com/hm4rk3tk to donate.
WHAT IS MS?
Multiple Sclerosis (MS) is typically first diagnosed in people in their 20s and 30s, with three times as many women as men affected.
The central nervous system condition is caused by damage to the coating around nerve fibres which is called myelin.
This causes a wide range of symptoms including vision and balance problems, dizziness and fatigue.
More than 100,000 people in the UK have MS. Once diagnosed, MS stays with you for life, but treatments and specialists can help people to manage the condition and its symptoms.
Research into a cure is progressing fast. Visit mssociety.org.uk for further information on th condition and ongoing research.