Watching the London 2012 Olympics with her twin sister Lina, Laviai Nielsen was just a teenager dreaming about what it might feel like to compete on the Olympic track herself. The sisters had volunteered at the Games and even carried Jessica Ennis-Hill’s kit, an experience that made Laviai want to become an Olympian one day. Nearly a decade later, she finally got that chance in Tokyo. But just two days before she was due to fly to Japan, Nielsen received life-changing news that would turn her long-awaited Olympic debut into one of the hardest moments of her career.

Nielsen’s body had started sending her unusual signals in the weeks leading up to the Games. She first experienced numbness in her arm, but initially thought she had simply slept awkwardly or that the sensation was linked to a new exercise at the gym. Then the problem became harder to ignore. After races, she began losing feeling in her legs, describing the sensation as similar to an “electrical shock.”

“It hit me like a truck that it wasn’t normal to lose feeling after races,” Nielsen explained to The Telegraph. “It’s normal to have lactic acid, but not lose feeling.” The first doctor she saw did not immediately identify what was happening. Her symptoms were instead attributed to stress, anxiety, competing and even overtraining. But Nielsen had another reason to take the changes seriously. Her twin sister Lina had already been diagnosed with multiple sclerosis, so Laviai decided to seek a second medical opinion.

Within about 10 days, she received the answer she had been looking for, but it was not the one she wanted. Nielsen was diagnosed with multiple sclerosis, an autoimmune disease that affects the brain and spinal cord. The timing made the news even more difficult to process because she was only two days away from flying to Tokyo for the Olympics. Still, she traveled to Tokyo by plane. But arriving in Tokyo did not bring any relief.

The Games were being held under strict COVID-19 restrictions, and Nielsen was identified as a close contact of someone on her flight who tested positive. She was forced to self-isolate shortly after arriving in Japan, leaving her alone to process a diagnosis she had received only days earlier. “That was probably the worst thing that could have happened to me post-diagnosis,” Nielsen said.

Yet, despite everything she had been through, Nielsen still took to the track in Tokyo. She lined up alongside Jodie Williams, Ama Pipi and Tiana Daniels in Great Britain’s women’s 4x400m relay team, which finished fifth in the final. But after that, she continued to train and compete while learning how to understand the changes in her body and manage the condition alongside the demands of elite sport.

The challenge became clearer again after the Paris 2024 Olympics. Nielsen had just returned from another Games, where she won bronze medals in both the mixed and women’s 4x400m relays.

But after getting home, she struggled with intense fatigue and brain fog. At first, she thought she was simply being lazy. Eventually, she realised that what she was experiencing was MS-related fatigue, something she had not dealt with at that level during the three years since her diagnosis. Over time, Nielsen has had to learn that recovering from those symptoms is not the same as giving in to them. Instead of always pushing through, she has become more willing to slow down when her body tells her it needs a break.

That is part of the reason Nielsen is now opening up more about her experience with MS. Nielsen wants to change that perception, both for herself and for other people living with MS. She and Lina have spoken to younger people with the condition and tried to show them that receiving a diagnosis does not necessarily mean giving up on the ambitions they had before it. “I think it’s very, very important for us to share being vulnerable,” Nielsen said.

And despite everything she has been through, Nielsen has continued to compete at the highest level.

Laviai Nielsen’s post-Paris comeback keeps Olympic door open for LA28

Nielsen has remained active throughout the 2025 season, racing over 400m indoors and outdoors before representing Great Britain at the World Athletics Relays in Guangzhou. In February, she finished third in the 400m in Metz in 51.88 seconds, third in Liévin in 52.58 and second in Toruń in 52.01. She later ran 52.02 at the Doha Diamond League in May and also competed over 200m in Philadelphia.

Her relay season brought another opportunity to compete for Great Britain. At the World Athletics Relays in Guangzhou, Nielsen ran the women’s 4x400m alongside Emily Newnham, Lina Nielsen and Nicole Yeargin. The British quartet won its repechage in 3:24.46, securing a place at the World Championships in Tokyo.

Nielsen carried that momentum into 2026. She returned to the track and continued racing over 400m, recording a season-best 51.02 seconds in College Station in June. She was also selected for Great Britain’s World Athletics Relays squad in Gaborone, again featuring in the women’s 4x400m.

Later in the year, Nielsen made her Commonwealth Games debut for Team England in Glasgow. She ran in the mixed 4x400m relay, helping England win its heat before competing in the final. The team went on to claim silver in 3:11.58, with Nielsen running the anchor leg.

With Nielsen still competing at the international level, the next question is whether she could extend her career into the Los Angeles 2028 Olympic cycle. She has not publicly confirmed LA28 as a personal target, but her continued involvement in elite 400m and relay competition means another Olympic appearance cannot be ruled out as she moves toward the next Games.