"There's only one hard and fast rule in running: sometimes you have to run one hard and fast."

Friday, August 1, 2008

Why are men faster than women, anyway?

In the addendum to my last post, I mentioned the lengths to which the Olympics are going this year to separate the men from the women. While it's generally agreed that women are at a disadvantage [full disclosure: I put in age and gender classes in the Fab 5 series only to increase participation], no one's been able to say just why men run faster than women. Here's the various theories.

Size theory: Men are larger and have larger hearts and lungs

The problems with this theory are many. A friend of mine thinks races should have height divisions and that, being a foot shorter than me, she has to take 50% more steps in any race than I do and that's why I'm faster. Sprinters do tend to be tall, but it's been shown rather elegantly that size is a disadvantage in the marathon. Men's hearts and lungs are in the same proportion to body size as women's - volumetrically, smaller is more efficient; this might be why small children seem to be able to play forever.

Untrained men do average higher maximal oxygen uptake levels than untrained women and the measurements among elite athletes show similar differences. This might account for some of the differences in racing, but not all; those with the highest VO2max readings are not the best runners (actually, the highest are in skiers) and oxygen uptake is irrelevant in sprinting, where men are still faster than women.

Composition theory: Women have less muscle and more fat

This is an easy, attractive theory, but doesn't withstand scrutiny. Female bodybuilders are very muscular and some in contest shape have had almost no body fat, but they aren't very good runners. Gayle Olinekova, a Canadian marathoner and bodybuilder, was the only cross-over of which I can think. The most muscular men don't win races, nor the ones with the least bodyfat (though, of course, bodyfat is dead weight and does slow one).

Heat transfer theory: Women dissipate heat less efficiently

I've never seen this discussed, but I think it's interesting. Men sweat more than women and women often supplement sweating by skin flushing, which isn't as efficient. Moreover, men sweat most from the chest, forehead and back (protecting vital organs), whereas women sweat most in the underarms (used for sensory signaling - there's some interesting data here I won't go into).

If this were all-important, then women would excel in cold weather races and do much worse in hot weather races. Though there is some anecdotal evidence for this, there's no good evidence.

Brain chemistry theory: it's all hormonal

Hormone differences do make men more likely to take risks and to compete harder as a result. This can be overcome by training and experience.

Multivariable theory: it's all of the above (and more)

While none of the theories above are sufficient to explain the differences between men and women, some say that each has a role and together they explain it. This is much harder to disprove, but one can do multivariable analyses; thus far, it's inconclusive.

Social theory: Girls are dissuaded from competition

In most societies, women running is not as acceptable as men running. I've heard many women claim that their running has been hampered by societal influence. The beauty of this claim is that it is completely untestable. If society is to blame, then societies that are more restrictive to women should have greater differences between the sexes; the number of great Algerian, Moroccan and Ethiopian women runners refute this. Though there is scant evidence, the difference between identical female twins raised separately is not substantially different from identical male twins raised separately.

Statistical theory: Fewer women run

This was a favored theory forty years ago. In any population, there is a bell curve distribution in abilities. The best times are in the extreme ends of the curve. Smaller populations have fewer numbers in the extreme ends and so the most extreme case (world record) is less likely to be as far from the median.

The problem with this is that the medians are different and the number of women running is almost the same as the number of women, unlike even a generation ago.

What a theory needs

Any theory trying to explain why men run faster than women needs to consider the following: 1) Boys and girls compete about the same until puberty. 2) The difference between men's and women's records is about 10% at every distance. 3) The difference between the median men's time and median women's time is also about 10% in many large races.

The difference has to be anatomical, independent of speed or distance. The difference has to be greater between the sexes than within either sex.

My theory: inefficient hip angles

Boys and girls hips are similar. Women's hips differ from men's in order to more easily bear children and this difference leads to inefficient hip angles. This difference would affect every step, so it would be true from sprints to ultras.

No study has been done. Casual observation does show that faster women tend to have narrower hips than slower women, but this is largely a matter of fat deposition. The best women runners do seem to have boyish hips, but again, the actual angle measurement can't be eyeballed. I knew one national class woman runner who had quite wide hips - her brother was also a national class runner, so she might've just lucked out on every other measurement - but she also had a broad back and shoulders, so the hip angle might have been slighter than it appeared.

Last word

I have no opinion as to why men are better bowlers or race car drivers. Nor do I care.


Lisa said...

Interesting, interesting. Love the summation of theories. I do wonder how much the Q angle affects things. Lean towards it being multifactorial.

Heat transfer was something I had observed, but didn't know it was based in fact. I have always said I do not tolerate the heat well because I essentially steam in my own skin vs the guy(s) I know who are dripping sweat. True in the sauna as well as on the trail!

Wonder if hormones/what our bodies are designed to do plays a role. Despite modern opportunities, women's bodies are - for the most part - designed to bear and nuture offspring. Millenia have honed that ability. Maybe that detracts from speed and in another millenia or two things will have changed and women will be just as fast (and men can bear and nurture offspring ;-> )

sea legs girl said...
This comment has been removed by the author.
sea legs girl said...

(sorry I had to erase and post again)

I love this post, Steve. I just have a few thoughts.

I think VO2 max is the biggest player in men vs. women.

I don't think heat dissipation plays a big role. Interestingly (and as a bit of a corollary to what Lisa said), pregnant women are super good at dissipating heat. They basically don't heat up when they exercise (well, a little) and that's from vasodilation. And they don't become super athletes as a result of this. Great point about the cold weather running, too.

And as for hips. Well, it doesn't explain why men are better swimmers. And I would say the discrepancy between men and women in swimming is about the same as in running.

Finally, I liked your theory about 21 hydroxylase deficiency in Jarmila Kratachvilova.

Londell said...


You must be a god! To post this well thought out analysis and get great replies from women. You walked where few men dared to walk and lived. Kidding a little. I know the night run is on next week! Cool if you could join us but even in the night it will be hard to keep up with you. You are a rabbit and I the turtle.

Diane said...

Good post!

Are men better bowlers than women? That's probably not due to the willingness to take greater risk.

MN Ultra Runner said...

What does Noakes have to say on the subject? I don't have my book available, I'll look it up this week and give you my interpretation of what he says.

Anonymous said...

Great post Steve. I've always wondering if the smaller runners had some kind of an advantage and you kinda touched on that 'elegantly'. Can you point to some reference on this? I'd love to read up on that. Thanks.
-Bob (Joel Button's friend - stayed with us before Leadville last year)

SteveQ said...

Bob, the most accessible discussion of size and runners is in Tim Noakes' book "The Lore of Running," where he covers the effect of surface area on heat loss in marathoning.

Tracy, the problem with VO2max is that it's trainable. If you eliminate the variables of body mass, stroke volume and maximum heart rate, men outperform women with the same VO2max. The men are therefore more efficient and that can only be due to men training better (an argument I certainly won't make!), an unknown biochemical difference or a structural difference.

Diane, they do separate men and women in bowling due to the best men having higher averages. Earl Anthony became world champion after having a heart attack (same year) - that's risk taking.

Anonymous said...

It is the hip angles, I've read up on the subject and the most current data suggest that the inefficiency of the hip angles of women, which forces them to sort of 'waddle', creates a need to put in extra effort during running, enough to have their maximum running speed potential lowered below mens. It's all biology.

Anonymous said...

thanks, helped with my GCSE statistics as our theme is track and field.

Anonymous said...

good post, but i think if a top woman athlete ran the speed of say mens 1500 they would be able to keep it up for at least a third of the distance. what would keep them from going the rest of the way?

mike shabetai said...

most interesting. However there r 2 points. First is max speed in 60 or a hundred meters (also velocity at start) However if women can run the speed of a 5km pace why r they also slower at long distance? No answers but just wondering