|By Ed Harry, BBC World Service Sport|
Paralympic champion Tatyana McFadden has chosen not to take part in a global charity race after organisers Red Bull banned racing wheelchairs.
Last year, the 26-year-old took part in the inaugural Wings for Life race, which raises funds for research into a cure for spinal injuries.
This year's event takes place on 3 May at locations across the world.
"It's been really, really hard to see that limitation put on the event," she told BBC Sport.
Russian-born US wheelchair racer McFadden took part in last year's Florida race using her racing chair, but now the rules have been changed and wheelchair users are required to compete in their day chairs and must also be accompanied by a support runner.
"They should have the option - people have different definitions of running. To tell athletes in racing chairs that you can't compete sends a strong message," she added.
The race uses a car to catch runners until only the winner is left but Red Bull have told the BBC that this concept doesn't work with racing wheelchairs, because of the speeds they can reach (30-40kph). To catch them, the cars would need to travel faster too - creating a safety issue.
Red Bull also say that at least 600 people have signed up to race in their day chairs with support runners, a tenfold increase on last year.
The 11-times Paralympic gold medallist Baroness Tanni Grey-Thompson says that she believes Red Bull's solution is the wrong one and the way to resolve the issue would be to have a separate category for wheelchair racers.
The International Paralympic Committee say it would be inappropriate to comment on an event which is not being run by the IPC but they told the BBC that Tatyana is one of the world's best Para-athletes and they fully understand her frustrations, however, what organisers do with their event is up to them.