What She Said: “Unmything the anatomy myth.”

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What She Said addresses one of the subtleties of male and female bike fit – and, of course, how it’s sold.

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Let’s imagine that the differences between men and women can be classified in a manner resembling the Dewey Decimal System.

Among the categories would be things like genetics, psychology, ability to ask for directions, shopping – and for fun, let’s add in anatomical differences.

Now, you might have noticed that there are some obvious physical differences between men and women that help with simple things like identifying the gender that a person is. And that’s good. But if you were hoping that I would talk about boobs, I’m sorry to say that’s not what I’m addressing now.

It’s not about proportions. It’s about centre of gravity.

There is a fundamental distinction between male and female physiology that has a significant impact on what women experience when they ride bikes. If you were to survey ‘industry experts’, you might hear that this is something along the lines of women having longer legs and shorter torsos than men.

This is a myth.

I’ve tried to trace the origins of this fallacy, and have yet to find its etymological root. Somehow, it became something that ‘they say’, and thus was adopted as fact. But it isn’t. What’s worse, is that ‘industry experts’ continue to perpetuate this myth, like product experts continue to suggest that the term monocoque means ‘one piece’ (it doesn’t).

There's more than one way to shift your COG...
There’s more than one way to shift your COG…

There is no study anywhere that conclusively states that one gender exhibits one type of proportionality as a characteristic of that gender

The problem with the letting this notion exist and not killing it with fire, is that it suggests that changes to women’s bikes were done based on something that isn’t true. If you want an example of REAL marketing hype, then look for things that say ‘this bike is designed to address the fact that women have longer legs and shorter torsos than men’, and you will have a bona fide example of a marketing statement that is simply made up.

There is no study anywhere that conclusively states that one gender exhibits one type of proportionality as a characteristic of that gender. Proportions are all over the map, and in reality, women typically have shorter legs than men in relation to overall height.

It’s not about proportions. It’s about centre of gravity.

Skeletal structure differences between men and women result in a different COG placement. In women, the COG is in the general vicinity of the lower back. In men, it’s slightly higher. So what, you say. What difference does an inch or two make? Loads, actually. Think about the difference between a bike with 120mm of travel versus one with 140mm of travel. Small change. Big result.

That geometry works well for lots of men, too.

In the case of bike fit, that COG placement means that a woman who is forced into a position whereby she’s leaning over too far, or is too stretched out, has more mass channeled away from the muscles that are designed to support the weight of the upper body: our good friend the core. Instead, the lower back is engaged and tasked with not only keeping the body balanced and centred, but also bearing a bunch of weight that it’s not meant to cope with for a prolonged period.

As an aside, centre of gravity is also why rear suspension on mountain bikes is sometimes more difficult to set up for women. For a lightweight rider, it can be a challenge to get enough pressure into an air can without sacrificing the performance of the suspension. It’s for this reason that a slightly altered leverage ratio on women’s full suspension bikes makes sense. It allows the suspension to perform well for a lightweight rider whose COG is focused more towards the rear of the bike.

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Bike fit is, of course, subjective. There are plenty of examples of women and men with gangly legs and the torso of a field mouse, and tree stump legs affixed to torsos resembling a Stretch Armstrong doll being used as a tug of war rope. Core strength plays a significant role in how easily a woman can adapt to a more aggressive lean angle on a bike, but in the absence of ‘abs of steel’, starting with a platform that addresses center of gravity placement is an easy way to guarantee that a woman, or anyone, will be in their happy place on a bike.

Bike fit is, of course, subjective.

There are lots of other issues about bike fit that play a role here that I’m leaving out, but in general the location of COG is why bikes with shorter top tubes and taller head tubes work so well for huge numbers of women. It has nothing to do with leg or torso length, particularly as proportions don’t change the fact that centre of gravity is still wherever the torso and legs meet, they only impact how far that COG is from the ground.

So, next time you or someone you know contemplates the value or hype of bikes with different geometry for women, help dispel the myth that any geometry changes that exist are because of proportionality. They aren’t. And in truth, that geometry works well for lots of men, too.

Read more opinions from What She Said


Comments (12)

    ‘the fact that centre of gravity is still wherever the torso and legs meet’ Any references for this? Does COG differ for pear or apple shaped body type and does it vary with BMI for the different body types?
    Caroline

    monocoque – One legged chicken, right?

    “but in general the location of COG is why bikes with shorter top tubes and taller head tubes work so well for huge numbers of women”

    I’m calling ballcrocks sorry. I suspect it is simply because on average women are approx 15cm shorter than men, see here: http://en.wikipedia.org/wiki/Human_height for a world wide breakdown on heights!

    Hi Caroline, a person’s somatotype (body composition/shape) won’t really impact COG placement, but will impact centre of mass. The principles will still apply to bike fit, though.

    Maxtorque: Not sure what you are suggesting isn’t true, but just to clarify the location of centre of gravity within the body isn’t based on a persons height. It’s based on gender. Height is a proportion, and as such will again only determine how far off the ground the COG is.

    It’s true that a woman who is 6′ tall will have a higher COG from the ground than a man who is 5’2, but within her body the COG is still going to be wherever her torso and legs meet. His will still be slightly higher in his torso than that.

    Make sense?

    “Where her torso and legs meet”
    COG. My arse.

    Not sure what you mean there, Clover. Feel free to elaborate.

    Center of gravity and center of mass are in the same place when in a uniform gravitational field. If you were taller than Mount Everest you would feel a 0.04% difference in gravitational field strength from feet to head, and less in the position of the CoG/CoM i.e. basically unnoticeable and they would still be roughly in the same place.

    There’s some interesting stuff in the article but I’ve found some of it hard to read…

    Hi Bonty,

    What did you find hard to read? I’d be happy to clarify anything.

    Long story short:
    -Women do not typically have longer legs and shorter torsos than men as a factor of gender.
    -Centre of gravity is located lower down the sagital plane in women than men. This is due to the difference in width of the pelvic girdle, and shoulder width.
    -The latter is why bikes with shorter top tubes and taller head tubes work so well for many women (and even many men).

    You’re saying that my centre of gravity is my beautiful and shapely posterior?

    Cyclenaut said “sagital plane” & “pelvic girdle”.

    Is it me, or is it getting HOT in here!! 😉

    (back on topic, i suspect things like CofG matter much more for road bikes than mountain bikes, as you move whole lot less when riding those! )

    Boing said Zebadee?

    I’m not working at the moment, something I find I am not averse to, but when I was working in the bike trade I was selling lady’s bikes on the back of the various articles I had read in bicycle magazines, including Singletrack, on the topic of women-specific-bike-design. I don’t have a spare hour to dig those out right now, but I am reasonably certain they-including Singletrack- advanced the myth you are now debunking, of ladies with shorter torsos and longer legs.

    In due deference to you, when I do go back into work, I shall alter my usual sales pitch, and include this new take on the matter, with an explanation that I haven’t had the opportunity to measure loads of women, so cannot be sure what the actual truth is!

    I know a yoga teacher who kept on boring us with talk of sagital movement! I did eventually work out what he was talking about.

    He has suffered for his art and his wisdom, because he is now officially know as “Sad Git”.

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