In part two of Gender and Sex, we discuss the ludicrous idea that the Nazis entered a man into the women’s field of running, “nude parades” at the Olympics, the effects of gender transition on athletic performance and grading, rules governing trans-athletes, and a summary of our off-microphone interview with Kai Scott on how running clubs can be more trans-inclusive.

Science Discussed:

The effect of testosterone on red blood cells and natural variability in testosterone

Since formal tests for female eligibility were introduced in 1966, no man has been identified in a women’s event at international competitions

An interview with Joanna Harper, medical physicist, distance runner, and adviser to the IOC on transgender issues

The history of “gender testing” in the Olympics

Latest research on the prevalence of transgender people in the USA

Hormone replacement therapy for transgender people

Trans women run slower after hormone therapy

Adding or blocking testosterone has major effects on muscle mass and hematocrit

Trans women are no faster than cis women

Transgender people have no competitive edge over cis people

Comprehensive list of athletic trans policies

An interview with Chris Mosier, trans athlete.

Wondering how you can make your running club or other athletic team more trans-inclusive?

Check out TransFocus or the Vancouver Frontrunners’ trans policy for an example.


Episode 5: Gender and Sex – Part 1

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





No shirt, no shoes, no service…. But you might just be able to win an Olympic marathon. Minimalism burst onto the running scene with the publication of Born to Run in 2009, claiming that running barefoot was more natural and would lead to fewer injuries. Since then, the scientific community has been working at catching up, testing to see which claims hold up to scrutiny and which don’t.

It takes the scientific community some time to do their work, so we decided to look at how people’s interest in barefoot running preceded the scientific community’s ability to study it.


So we gauged people’s interest by looking at Google search trends for the phrase “barefoot running”, and found it peaked in 2010.  Publications on Web of Science (which only indexes scientific papers) peak in 2014. I kind of suspect if you did a similar analysis for “Atkins diet” you’d probably find something similar.  It takes the scientific community time to catch up to all the claims made in the popular press.

So what have scientists found? Well so far it looks like running in minimalist shoes or barefoot doesn’t guarantee you’ll switch to a forefoot landing gait, and while you might get fewer hip or knee injuries, you’ll increase your rate of foot and ankle injuries.  

So pick your poison!

Literature cited:

Position statement on barefoot running by the American Podiatric Association

Running shoe technology has progressed for 30 years, but injury rates have not

Defining minimalist shoes

Stress fractures when you switch to minimalist shoes too fast

Foot bone marrow edema after switching to minimalist shoes

Harvard cross country runners who heelstrike have greater injury risk

Impact forces are greater in Nike Frees (minimalist) than Nike Pegasus (traditional)

Switching shoes doesn’t necessarily mean you’ll switch gait

Western Kenyans who grow up barefoot are more likely to forefoot strike

Plenty of Tarahuamara people heelstrike

There are other Kenyan people and Tanzanian people who grow up barefoot and also heelstrike

People often don’t know how their foot strikes

Minimalist shoes increase rate of injury in a 10 km training program

Barefoot runners have fewer injuries, but run less than traditional shoe wearers

Review of injury risk in barefoot running


First it starts with a 5K. Next thing you know your child has moved onto a 10K, then a half marathon, then even a full marathon. Spending hours every week feeding this disgusting habit. And by disgusting I mean nipple chafing and foot blisters.  

Why do people run? In our last episode we talked about the health benefits of running, which I’m pretty certain a lot of people probably run for that reason, maybe even exclusively, or at least get started for health reasons — but MAYBE lots of people also run because… well… they get high.

What do we conclude?

It seems pretty clear that you can get high from running.  Now, whether this is relatively mild changes in pain perception, or slightly elevated mood following running, or getting outright blitzed mid-run seems to vary between runners, but it’s good to know at least the mild form is repeatable!  We still don’t really know the mechanisms–there might be endorphins, but that’s a hard thing to be sure of.  Endocannabinoids seem like a pretty likely candidate too, but the case is far from settled!  The best evidence we have suggests that a 30 minute run at 70-80% of your maximum heart rate (not too fast!) seems to make most runners feel good.  

Smoking pot recreationally before running doesn’t seem to have the negative effects you might think it does–since it’s a bronchodilator. But since it also increases heart rate, it doesn’t seem like it would be helpful to smoke up pre race (maybe just for a training run). Whether or not pot is a performance enhancing drug is still being sorted out, but there’s no blaring sign that you *shouldn’t* occasionally smoke up before running if it’s legal in your jurisdiction.  Just take ‘er easy.

Studies mentioned in this episode:

Getting the runner’s high is pretty common

Old definition of the runner’s high as a “transcendental” experience

New definition of runner’s high

The runner’s high as a placebo response

People who think the runner’s high is a myth

Blood plasma levels of endorphins increase after exercise

More endorphin studies

Yet more endorphin studies!

And more!

PET study showing possible endorphins in the brain

Naloxone doesn’t block the mood effects of therunner’s high

Naloxone does seem to block some of the pain relieving effects

Review suggests the endorphin hypothesis has little evidence

A review of the endocannabinoid system

First evidence of endocannabinoid release in runners

Review of exercise and the endocannabinoid system

Optimal running dose for endocannabinoid release

Running in adolescence reduces cannabinoid receptors in rats

Knocking out cannabinoid receptors decreases wheel running in mice

Blocking cannabinoid receptors decreases running in mice

Exercise addition and endocannabinoids

Review of cannabis and sports

Judgement impairment following cannabis use

Cannabis use doesn’t always decrease reaction time

Old Canadian studies on pot use and cycling

Cannabis decreases grip strength

Review of cardiovascular effects of cannabis

Cannabis use increases heart rate

Cannabis is a bronchodilator

Potential use of cannabis as an anti inflammatory drug 

Review of effects of cannabis on exercise performance

Cannabis smoking doesn’t decrease lung function

Cannabis smoking doesn’t seem to have negative lung effects





Every six months or so, headlines proclaiming the doom of people who like to run seem to pop up like little schadenfreude sundaes.  People love to tell runners that all their hard work is likely causing more harm than good, and after the deaths of celebrities like Jim Fixx, Micah True, and even poor old Pheidippides (he of Marathon fame), it is a little scary to contemplate. But how good is the science behind this idea?  Are you really likely to die mid-run?

TL:DR version?

Exercise, any exercise at all, is generally good for you.  It will increase your lifespan, reduce your risk of diabetes, reduce excess weight, and more.  Most people don’t get near enough.  Do some people die during marathons?  Yes, but it’s unclear whether marathons actually elevate your risk of early death–those people had underlying structural abnormalities or atherosclerosis already.  And the clinical significance of any kind of heart damage marker following extreme exercise is unclear–long distance athletes live longer than sedentary or even moderately active people, so it doesn’t appear that these markers mean anything in this population.


  1. What is the right amount of exercise for maximizing lifespan?  “I have no idea — though my answer for 99.99% percent of people would be “More than what you’re doing right now.” — Alex Hutchinson, science writer
  2. Remember Jim Fixx–lots of running won’t fix a bad diet
  3. If you’re feeling weird, talk to you doctor! Some cases of hypertrophic cardiomyopathy and athersclerosis can have symptoms like heartburn, tightness in the chest and arms.

Studies mentioned in the episode:

Pheidippides probably didn’t die

The rate of cardiac arrest in marathons is 1/184,000 participants

Atherosclerotic heart disease tends to be the cause of death during marathons

Marathons prevent deaths from traffic accidents

Cardiovascular disease is the leading cause of death worldwide

Even small amounts of running massively decrease your risk of death from heart disease

Among runners, those who run more need fewer diabetes and cholesterol-lowering drugs

Similarly, more intense running reduces diabetes and cholesterol drug use

Student athletes have fewer heart attacks than the general population

Most people are less active than they think they are

Copenhagen heart health study about risks of strenuous jogging

O’Keefe softens his stance, says 5-6 days of running/wk for total of less than 5 hours is probably ok

Running helps prevent diabetes, high blood pressure, and cardiovascular disease

Marathon runners have higher rates of markers of heart damage

Recreational Boston Marathon runners have elevated markers of heart damage following the race

Ironmans do not cause increases in heart damage markers

Recreational Berlin Marathon runners have elevated markers, but no indication of actual heart damage

Elevated heart damage markers following exercise likely are not meaningful

Cardiac arrhythmias are reduced following marathons

Alex Hutchinson attacks the “running too much” myth


Cover photo by mebrett is licensed under CC BY 2.0


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Hi all!

Every other week I’ll be giving a quick overview of the new and exciting running research that piqued my interest.  See what the intrepid science of running community is up to!

Runners who have never been injured land more softly

Strength of evidence: 2/5

Strength of effect: 2/5

Runners develop injuries on a pretty regular basis, and ideas about how to avoid injury are a dime a dozen.  One hypothesis is that landing more softly can reduce the risk of injury by decreasing the amount of force that the leg has to absorb.  However good tests of this hypothesis are few and far between.  In this prospective study (meaning that participants were identified ahead of time and then tracked), 249 female runners were grouped by their injury rate, and their vertical landing force while running was measured.  The researchers found that runners who were never injured landed with significantly less force than runners who had diagnosed injuries.  While this study is some of the first evidence that landing force is related to injury rate, the number of runners who were never injured was very small (21 out of 249 total), and in general, there was no significant relationship between injury rate and landing force.

New leg muscle found!

Strength of evidence: 2/5

Strength of effect: N/A

The human body has been poked and prodded inside and out for thousands of years, but it still seems to have many secrets in store for researchers.  Most recently, scientists have found that a muscle has been hiding all along in the upper leg.  Hiding in between the vastus lateralis and the vastus intermedium (two of the quadriceps muscles), the new muscle has been dubbed the tensor VI, and was found in all 26 cadaver legs that researchers dissected.  They also identified four different versions of the muscle: intermediate type (found in 11/26 legs), VI type (found in 6/26 legs), VL type (found in 5/26 legs), and common type (found in 4/26 legs).  Whether these different subtypes have any impact on leg strength or function remains unknown.

Women runners of all sizes experience breast pain

Strength of evidence: 4/5

Strength of effect: N/A

Running involves a lot of moving parts, and many runners find that, unfortunately, this includes breasts.  A study of 1285 female runners who participated in the 2012 London Marathon found that 32% of them experienced breast pain. The chances of having breast pain increased with cup size and decreased with having had children previously. Seventeen percent of the women experiencing breast pain said they reduced how much they exercised as a consequence.  Surprisingly the researchers found that despite the relationship between cup size and probability of experiencing pain, over 20% of A cup wearers still experienced breast pain, so pain (or lack thereof) can happen to women with any sized breasts. Finally, most women (>40%) did not do anything to deal with their breast pain, 20% used a sports bra, 15% used pain medication, and 13% just held their breasts.  Yeowch!

Strength of evidence: This is a measure of how many participants were in the study: 1 = 10 or fewer, 2 = 100 or fewer, 3 = 1000 or fewer, 4 = 10,000 or fewer, 5 = 10,000+

Strength of effect: This is a measure of how much of a effect was found.  Not every study will have this, but for those that do, we will base it on the odds ratio, which is the multiplier of 1 which is the control (e.g. so if eating eggplant gives you OR of 2 for developing bad breath, you have double the risk of getting bad breath as someone who doesn’t eat eggplant): 1 = OR of 1 – 2, 2 = OR of 2 – 3, 3 = OR of 3 – 4, 4 = OR of 4- 5, 5 = OR of 5+

Cover photo by Gary Lerude is licensed under CC BY 2.0

So after many many unfortunate events that involved a lab flood, a pair of stolen and destroyed glasses, and more rain than any person should have to stand, we’re happy to present our first podcast!  Alcohol and running–how they mix, should they mix, and what terrible things might happen in the event of their mixing.

As we produce each podcast, we’ll make sure we link up all the studies we cite in the podcast, so here they are in order of mention.

Did you know you can win an Olympic Marathon while eating a combination of brandy and strychnine?  Or that the world mile record while drinking beer is only just a minute slower? Turns out good drinkers can be good runners.

TL:DR version?

It’s not entirely clear what impact alcohol has on athletic performance.  It certainly isn’t a great idea to get drunk before running, but moderate alcohol consumption on a general basis will likely not do any harm.  You’ll also probably be able to run just fine while moderately hungover, but like any other time you run, gauge how you’re feeling and make sure you’re well hydrated.   As for that post-run beer?  Keep it to one or two and you won’t be undoing your good work, but it’s probably not a great idea to have more than that (and that’s probably good advice in general!).

The story of Thomas Hicks

Running increases rat ethanol preference

Runners drink more than non-runners

Exercise on any given day increases the chances of consuming alcohol

Drinking before a run is a bad idea

The Beer Mile!

Hangovers don’t decrease running performance the next morning

VERY hungover mice have a harder time running

A small amount of drinking after a run doesn’t cause problems in muscle repair

A larger amount of alcohol can decrease recovery of peak performance

A small amount of alcohol doesn’t change glycogen replenishment, as long as you eat enough

Drinking a small amount of beer after a run doesn’t worsen dehydration

Enjoy all the sciencey goodness!


Cover photo by digboston is licensed under CC BY 2.0

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