Latitude, Limb Length, Squatting and Sex

Perusing the articles on my blog, you will find that I have a predilection for writing about squatting. The most conclusive research to date on the factors effecting deep squatting range of motion indicates that the ankle is the key variable. If you have excellent ankle dorsiflexion range of motion, chances are you will be able to easily get into a deep squat.

Squatting: Little Kids with Little Limbs

Of course there is more to deep squatting than just ankle range of motion. While observing the squatting of toddlers I noticed that many of them have nearly vertical shins, literally using no ankle dorsiflexion range of motion at all. They are able to do this because toddlers have proportionally tiny legs, long torso’s, and big heads.

front-squat-baby

Notice the vertical shin of the toddler above from the crossfit ignite syndney website. It is true that we all could deep squat easily when we were toddlers but as we grow into our adult bodies, deep squatting gets considerably more difficult for some of us.

If you have any difficulty deep squatting with your heels down, you will notice that you always fall backward, not forward.

In order to balance one must have:

1) equal weight in front and behind one’s center of mass

2) one’s center of mass over their base of support (ie feet).

As one squats down lower with the heels down, the weight of the upper thighs, hips and lower back shifts towards the back of the foot.

Eventually this weight will cause you to fall over backwards unless:

1) Your ankles bend (dorsiflex) to allow your body to move forward

and/or

2) The weight of your head and shoulder is sufficient to counterbalance the weight of your hips.

The following body proportions make squatting easier:

Shorter thighs are better for squatting as the weight of your hips doesn’t get pushed back as far.

Longer torsos are better for squatting as the allow the head and shoulders to be further forward without rounding the back.

Heavier upper bodies are better for squatting as they provide more counterbalance in front.

Even if you have the opposite proportions as the ones above you can still deep squat comfortably if you have enough ankle dorsiflexion range of motion to compensate.

How Latitude Affects Squatting

Allens Rule states that warm blooded animals which live further from the equator will have shorter limbs to conserve heat because heat is lost more quickly through the limbs than the torso due to the higher surface area to volume ratio. The presence of this rule in living species has been explicitly validated in birds [Nudds] but the same principle applies for all warm blooded animals. In a laboratory test, humans with longer legs (specifically longer thighs) lost heat more rapidly that those with short thighs [Tilkins] I first heard about Allen’s Rule in The Sports Gene by Dave Epstein.

This the factors controling limb length were long thought to be only genetic, but recent evidence has shown that mice raised in a cold environment (7C) have shorter limbs than those raised in warmer environments (21 or 27C) [Serrat]. The decreased blood flow to the limbs in colder environments is at least partly responsible. [Serrat]

Smaller limbs means shorter thighs and a relatively longer torso, both of which would help with squatting. A moderate correlation between lower latitude and longer limb length  is present in humans although no direct relationship was found between latitude and sitting height (trunk length). [Cowgill]

In summary: Groups of humans who live in cold climates far from the equator (Inuit, Mongolians) have shorter thighs and thus have better proportions for deep squatting than those who live in hot climates closer to the equator (Kenyans, Sudanese).

Mongolian Squatting

Source: Travel blog “Letters to Jonathon”

Notice how far the knees are from the shoulders in the relatively short thigh of the Mongolian man above and how the knees are actually at the shoulder in the long thigh of the Dinka woman in Sudan below.

191Dinka woman squats as cooks fish040ZKR015

Source: Sudan photo archive

How Sex Effects Limb Length

By sex of course I mean gender.

 Other factors besides one’s latitude can have an affect on one’s body proporrtion, and many of these are commonly different between the sexes.

The average woman has longer legs and a shorter torso than the average man, thus making squatting slightly more difficult.

The average woman has a greater proportion of her body weight near her hips and a lighter upper body thus making squatting slightly more difficult.

Tall people have proportionately longer legs and shorter torsos thus making squatting slightly more difficult.

The tall woman with a light upper body and heavy lower body will need the most ankle dorsiflexion range of motion to be able to deep squat, but as in the photo of the Dinka woman above, it can still be done.

Summary

After a long discussion of all the body proportions that make squatting easier or harder that you can’t do anything about, I think it is worth repeating that ankle dorsiflexion flexibility is still the key variable. While ankle flexibility is partly genetic, it can be improved with stretching, and thus one can improve one’s squatting ability.

Here is simple low-load ankle dorsiflexion stretch for the ankle joint specifically.

2013-05-20 10.14.36

Here is a more advanced ankle dorsiflexion, only suitable for those without any knee problems.

2013-05-20 10.14.35-1

References

1. Nudds RLOswald SA. An interspecific test of allen’s rule: evolutionary implications for endothermic species. Evolution. 2007 Dec;61(12):2839-48. Epub 2007 Oct 15.

2. Tilkens MJWall-Scheffler CWeaver TDSteudel-Numbers K. The effects of body proportions on thermoregulation: an experimental assessment of Allen’s rule. J Hum Evol. 2007 Sep;53(3):286-91. Epub 2007 Aug 13.

3. Kaciuba-Uscilko HGrucza R. Gender differences in thermoregulation. Curr Opin Clin Nutr Metab Care. 2001 Nov;4(6):533-6.

4. Serrat MA. Allen’s rule revisited: temperature influences bone elongation during a critical period of postnatal development. Anat Rec (Hoboken). 2013 Oct;296(10):1534-45. doi: 10.1002/ar.22763. Epub 2013 Aug 19.

5. Serrat MAKing DLovejoy CO. Temperature regulates limb length in homeotherms by directly modulating cartilage growth. Proc Natl Acad Sci U S A. 2008 Dec 9;105(49):19348-53. doi: 10.1073/pnas.0803319105. Epub 2008 Dec 1.

6. Cowgill LWEleazer CDAuerbach BMTemple DHOkazaki K. Developmental variation in ecogeographic body proportions. Am J Phys Anthropol. 2012 Aug;148(4):557-70. doi: 10.1002/ajpa.22072. Epub 2012 May 24.

7. Christopher Ruff. VARIATION IN HUMAN BODY SIZE AND SHAPE Annual Review of Anthropology. Vol. 31: 211-232

One thought on “Latitude, Limb Length, Squatting and Sex

  1. Pingback: How Deep Should I Squat? | Posture Movement Pain

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