Allen's Rule: Is this why the Kenyan's are better marathoners ?
/Allen’s Rule
So you want to be the next great distance runner do you? There are some genetic components that might (or might not) come into play, things you obviously do not have control over.
Proposed by Joel Allen in 1877, Allen’s rule has in many respects been proven to have little scientific support. None the less, knowing and understanding the Rule has some value, especially if you are researcher J.S. Alho of the Ecological Research Unit of the Univ. Helskini, Finland where recent renewed interest in the rule has arisen due to global warming and the microevolutionary changes it predicts.
Allen’s rule states that endotherms from colder climates tend to have shorter limbs than those in warmer climates. The theory is based on the surface area of an organism. The larger the surface area the easier it is to dissipate heat, but also the easier it is too cool. Depending on the location the organism finds themselves, this can be an advantage or a disadvantage.
There is a theory (ecographical rules if you will) by Allen’s rule, that suggests that growth plasticity of the limbs and other body parts exists and which is correlated with the temperature conditions of the developing mammal, particularly during the periods of rapid skeletal development. Allen’s rule suggests that relative extremity length decreases with increasing latitude. Thus, according to Allen’s rule, those living on either side of the first degree of latitude from the equator (suggesting the hottest 138 mile or 222km swath on earth) should have the longest limbs (keep in mind this is likely a carried-forward genetic trait). This plasticity of the human skeleton allows mammals to adjust to the exposed temperature conditions during early development. This suggests possible advantages to climate rearing for would be world-class athletes depending on the chosen sport. For example, Allen’s rule proposes that individuals reared in hot climates will develop longer thinner limbs which have more surface area whereby they can irradiate body mass heat into the environment thus creating a net cooling effect of the body enabling physical exertion to occur longer and at a higher rate (appendage length correlates with temperature and latitude from which the mammal was raised). This is one of the theories proposed as to why Kenyan runners outperform so many other professional distance runners, long thin limbs seem to act as cooling vents. It is also one of those theories that seems to hold little water, but it is good to know none the less. Sometimes theories that are proven to be false come back to have some truth down the road. And maybe Alho will discover just this is the case in time.
Shawn and Ivo…….. The Gait Guys….pulling out random facts, some useful, others not so useful (and some proven debunked) to expand your gait knowledge. The more you know, ……… the better you are a cocktail parties. Tis the season !
References:
1. Anat Rec (Hoboken). 2013 Oct;296(10):1534-45. doi: 10.1002/ar.22763. Epub 2013 Aug 19.
Allen’s rule revisited: temperature influences bone elongation during a critical period of postnatal development.2. J Evol Biol. 2011 Jan;24(1):59-70. doi: 10.1111/j.1420-9101.2010.02141.x. Epub 2010 Oct 21.
Allen’s rule revisited: quantitative genetics of extremity length in the common frog along a latitudinal gradient.Alho JS, Herczeg G, Laugen AT, Räsänen K, Laurila A, Merilä J.
