There’s a reason we list gender and sex as separate topics in the title. That’s because, unlike what you might think, it’s not as simple as XX and XY chromosomes leading to male and female bodies which makes men and women. It’s biology–which is a notoriously complicated mess. It’s psychology–even more complicated! And it’s society all wrapped together.

Welcome to a very special edition of the SciRunner podcast featuring our first guest Tessa Fisher. Probably the world’s only queer, trans astrobiologist, the Arizona State University PhD student and avid runner helps Katie and Nigel explore the science and sociology behind gender and running. It’s a long one. So long that we’re actually splitting it into two episodes! Stay tuned for part 2 where we discuss running and transition.

What did we find?

On average, men run faster than women, and the difference seems to be more due to testosterone levels than different body characteristics (e.g. body fat). Sex lies on a spectrum, and the world’s experts on the topic report 20+ ways that someone can be somewhere between male and female. You can have XY chromosomes, have high testosterone levels, but be so insensitive to the effects that your external anatomy is completely female. This makes it hard to define gender categories in runners. In addition, the effects of endogenous (self-produced) testosterone on female running performance aren’t well understood, and don’t seem to have much of an effect.

Science discussed:

Position statement about sex and gender by the American Physiological Society

Male runners are about 14% faster than female runners

Body fat only explains about third of the difference in speed difference between men and women

Male greyhounds only run about 0.7% faster than female greyhounds

Overview of testosterone effects on running performance

Review of gender and running–hematocrit and testosterone.

Review of how sex is a spectrum

Article talking about how there is no single biological criterion for sex

Testosterone levels in female athletes vs. non-athletes

Height and Y chromosomes in female athletes

Olympic policies have led to medically unnecessary treatment of high testosterone in women

The history of gender testing in the Olympics & the IAAF concluding testosterone wasn’t important

Historical intersex conditions and women runners