England's Jordan Nobbs calls for research into ACL injuries and menstrual cycle
England and Arsenal midfielder Jordan Nobbs has called for more research into the links between anterior cruciate ligament injuries and menstrual cycles.
Nobbs, 26, was ruled out of this summer's Women's World Cup after damaging her knee in November.
She believes her period, which began the morning of the game with Everton, was "a very high factor" in the injury.
"Until I got injured I didn't really know that a lot of women do it while in their menstrual cycle," she said.
Research has suggested that ACL injuries - the most serious kind of knee damage - are more prevalent in female athletes than men.
One contributing factor is that oestrogen - a hormone released during menstruation - can increase joint flexibility, which could result in more damage if an athlete twists a knee.
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"I was very tired leading up to that week and I was on the first day of my menstrual cycle," England vice-captain Nobbs told BBC Sport.
"I'm not one for saying it was that, but the facts on how so many women have done their knee and been on their menstrual cycle is very high.
"I don't know if it was down to that but it was a very high factor."
The English Institute of Sport has launched a SmartHer campaign - supported by the Football Association - which prioritises female health and supports athletes.
Nobbs, capped 56 times by England, was ruled out of the World Cup in December and had surgery later that month.
"I didn't know much about ACLs and I didn't think I'd do mine - I was naive to that," she said.
"But I think, how much do our clubs and physiotherapists and scientists know about when we're on our menstrual cycle?
"There does need to be more research put into place and more knowledge, so they know when people go out to training they've done as much as they can to reduce the risk of a knee injury."
BBC Sport has launched #ChangeTheGame this summer to showcase female athletes in a way they never have been before. Through more live women's sport available to watch across the BBC this summer, complemented by our journalism, we are aiming to turn up the volume on women's sport and alter perceptions. Find out more here.