Paula Radcliffe set a new world 10km road race record in San Juan, Puerto Rico, on Sunday.
Sunday was Radcliffe's first race of the year
Defending her title, Radcliffe set a new mark of 30 minutes 21 seconds, shaving eight seconds off Asmae Leghzaoui's previous world record.
With Radcliffe and Moroccan Leghzaoui going head-to-head the race was always going to be fast.
But the British star said she was still a little surprised by her performance.
"I knew I was well clear of the field but I did not know what the distance was," she said.
"My run this evening tells me that I am probably in much better shape than last year. Honestly, I believe I could have run faster."
Leghzaoui finished behind the Briton in a time of 31min 35secs while Kenya's Esther Kiplagat came home third.
Radcliffe is getting used to smashing records after she sensationally broke the world marathon record in Chicago last October.
In just her second attempt over the distance she chipped a massive 89 seconds off the previous mark.
The Bedford-born runner is on course for another fine season but she is not sure if she will aim for the world cross country record in Lausanne.
"I have not yet made a decision about tackling the world cross country," she revealed.
"I will have to get back into training before making up my mind."
This winter, Radcliffe has been training in Albuquerque, New Mexico but she will return to Britain ahead of April's London Marathon where she has agreed to defend her title.