Mizuki Noguchi has undergone medical tests since returning from a training camp in Switzerland earlier this week in a move that could pose a serious threat to her bid for back-to-back Olympic women's marathon titles, sources close to her said Saturday.
Noguchi, 30, received an MRI earlier on Saturday for the second time since coming back from training in St. Moritz on Monday ahead of her original schedule citing fatigue. No other details were immediately available.
The MRI tests were aimed at detecting any changes in her muscles, according to the sources, adding that Noguchi will decide on her plans after holding discussions with medical experts.
They did not rule out the possibility that she could pull out of the Aug. 17 race in Beijing.
Noguchi is scheduled to leave for Beijing on Wednesday.