New research suggests women may be faster than men over 'ultra' long running distances.
Ultra races, or ultra running, is the name for are any long - distance race that covers more miles than a traditional marathon.
A study of more than five million race results concludes that the gap between the sexes gets smaller as the distance increases with women, on average, being slightly faster than men when the race is long than 195 miles.
Kelly Pepper from Stowmarket took up ultra running six years ago. Kelly who is also race director of Suffolk Trail Festival has been hooked on the sport ever since. She says for her, the appeal was that success of the race was purely on whether you finished the distance or not, and not that you needed to be the fastest runner on the track.
It's a sport that's becoming more and more popular across the region.
Claire Maxted from Stamford near Peterborough has written books about trail running and has competed all over the world. For her, there's an important social aspect to ultra running as you get to know a crowd of people while traveling such long distances.
It's long been assumed that men on average are faster than women when it comes to running but new research suggests the reality is more complicated than that.
The latest study looked at race results over more than two decades. It found that the longer the distance, the less difference there was between the sexes in finishing times. In fact in the really long races of more than 195 miles, women on average were slightly faster.
Over the 26.2 miles marathon distance, men ran 11.1 % faster than women - in races of 100 miles the difference was down to 0 .25 % - while in races of more than 195 miles, women were 0.6 % faster.
One theory is that women convert fat into energy more efficiently - giving them an advantage over men in ultra long distances. Another factor according to those behind the research could be psychological.
Sophie Power hit the headlines when she was photographed breast feeding her three month old son during an ultra race and the picture went viral. She's since made a documentary about running after pregnancy. She's wary of drawing too many conclusions from the research but does believe women can have advantages over longer distances.
Claire Maxted from Stamford near Peterborough loves running. It's taken her all over the world and she's written books about trail running - She took up the ultra form of the sport for some unorthodox reasons.