Britain's Laura Muir has revealed she does not speak to rival Genzebe Dibaba over the Ethiopian's links to a coach arrested as part of an anti-doping investigation.
Dibaba beat Muir to gold in both the 1500m and 3,000m events at the World Indoor Athletics Championships.
Her coach Jama Aden denies any doping offences, while Dibaba has always maintained she is clean.
But Muir's coach says the relationship is "not healthy for the sport".
Aden was arrested in June 2016 as part of a joint anti-doping operation by Catalan police, world athletics' governing body the IAAF and the Spanish anti-doping agency.
Dibaba has never failed a drug test and says she would ditch her coach if he were ever found guilty of doping-related offences.
But Muir, who won 3,000m bronze and 1500m silver in Birmingham last week, said she did not have a relationship with Dibaba and racing against her was "difficult".
"It can be difficult but I think I've always said that no matter who's on the start line, I'll race against them. The reason I'm in this sport is because I enjoy it and nobody is going to stop me from enjoying it," she added.
"It is what it is. All I can do is concentrate on my performances."
The Scot's coach, Andy Young, added: "[Dibaba's] association with a certain coach is not particularly healthy for the sport."
Dutch athlete Sifan Hassan, who won 3,000m silver and 1500m bronze, refused to smile on the podium in Birmingham, which was interpreted as a sign of how she also felt about Dibaba.
"We saw Hassan at the stairs, she was lovely, it was all great. I don't think she was expressing disappointment [on the podium]. I think she was expressing her contempt for the gold medallist and her associations," said Young.
When asked about Young's statements, Dibaba's agent Juan Pineda said Muir's coach was a "bad loser".