Four-time Olympic champion Laura Kenny has sustained a hamstring injury which casts doubt over whether she will compete in April's Track Cycling World Championships in Hong Kong.
The 24-year-old, who as Laura Trott won two gold medals at the London 2012 and Rio 2016 Olympics, was waiting to decide on her participation at the World Championships.
And in withdrawing from this month's Six Day event in Berlin and the British Championships at the Manchester Velodrome with a hamstring injury, with no timescale given for her return, Kenny's return to global competition may also be delayed.
British Cycling said in a statement: "British Cycling's Laura Kenny has withdrawn from the forthcoming Six Day Berlin and HSBC UK National Track Championships having sustained a hamstring strain.
"Laura is undergoing treatment and hopes to return to full fitness soon."
Six Day Berlin begins Thursday, while the British Championships take place from Jan. 27.
Riders often opt to miss the first World Championships following an Olympics to take a break early in the four-year cycle between Games.
Kenny married six-time Olympic champion Jason Kenny last September. The Hong Kong Track World Championships take place from April 12-16.