Running shoes anatomy 101
Heel-toe drop (or offset, or differential) is a term that came along with the boom of technology in running shoes, and the increasing interest in barefoot running. So what exactly is it, and why are people interested in it anyway?
First of all, one needs to know what the “stack height” refers to; and that is simply a measure of how much material is between the bottom of your foot and the ground.
Now, measuring the stack height at the heel and the toe and subtracting those numbers, will give you the heel-toe drop. To make things clearer, heel-toe drop has been defined by Brooks Running as “the difference between (midsole + outsole) heel height and (midsole + outsole) forefoot height” .
To put things into perspective, some realistic scenarios would be: heel stack 23mm, toe stack 11mm, giving a heel-toe drop of 12mm, or in another case, heel stack 18mm, toe stack 12mm, giving a heel-toe drop of 6mm. It is easy to see that the heel-toe offset indicates how “wedgy” the shoes are; the higher the number, the more your heel will be left higher than your forefoot.
Traditionally, running shoes have been built with a 12-15mm heel-toe drop. but the minimalist shoe movement of the last few years has brought about lower stack heights and smaller forefoot drops. Moderate minimalist shoes typically have a 4-10mm heel-toe drop, while, zero-drop shoes (heel-to-toe drop of 0 to 4mm) are also available, aimed to provide an as close as it gets “barefoot” running experience.
As far as to which are better for you, many studies have been published, and the argument that is often being made is that running in shoes with a larger heel-toe drop encourages a heel strike. This, in turn, can not only diminish running efficiency and speed, but can also potentially cause injuries, as it is associated with higher impact forces and greater rotational forces (overpronation). On the contrary, a lower heel-to-toe drop is supposed to encourage a midfoot strike, and help the runner maintain a natural position.