Photo: Loic Tregan / Twitter / @inov-8

Earlier this week, Jasmin Paris became the first woman to win The Spine Race, a 431km endurance running event in the UK.

The 35-year-old Scottish vet not only broke the previous record by over 12 hours – expressing milk for her baby on the way – she also finished a full 15 hours ahead of the next competitor.

Why is it that women are outperforming men in endurance events?

Research on female athletes and endurance athletes is lacking, according to Massey University sports science lecturer Claire Badenhorst, but she has some theories.

Photo: Claire E Badenhorst / Twitter

The reproductive hormones released during menstruation can improve a woman's ability to perform both physiologically and psychologically, Dr Badenhorst says.

Some women seem to excel physically after having a baby but there's not a lot of supporting scientific evidence behind that yet.

After childbirth, an increase of estrogen promotes a female body's use of fat as an (aerobic) fuel, she says.

Higher estrogen levels also result in women's bodies manufacturing less blood lactate, which can increase endurance.

After giving birth, women have increased progesterone levels, which can naturally promote increased respiratory drive and may extend aerobic performance and capacity, Dr Badenhorst says.

"Our natural physiology is maybe supporting us … but as soon as we start looking at the science over anything over a couple of hours we are largely basing it on theory."

It may be that women have increased red blood cell production and greater oxygen-carrying capacity after giving birth, she says.

"It could be that through the process of pregnancy an adaptation which people try to achieve through altitude training, is naturally occurring within female athletes."