Ale Santuz: Heel-to-toe drop: meaning and measurement                                                  

Heel-to-toe drop: meaning and measurement

In a shoe, the heel-to-toe drop (HTTD), also called heel-drop, is nothing but the difference between the heel and the fore foot height. Some people measure these values without including the insole, but I like more the approach that includes it (there is always an insole, so why forget about it? Moreover, some insoles have differentiated thickness from heel to fore foot).
Figure 1 shows the location of the outsole (usually the only part in contact with the ground, provides grip), the midsole (usually located between outsole and insole, provides cushioning) and the insole (also called insert, provides a small amount of cushioning and sometimes supports the arch of the foot).

Figure 1 Outsole, midsole and insole in a running shoe.

Typical values of HTTD can be classified (here you can find a list of some shoes I measured) as follows:
  • 0 to 4 mm - usually found in racing flats, "zero-drop" or minimalist shoes, generally low cushioned
  • 4 to 8 mm - usually found in racing flats or "low-drop" shoes, generally low cushioned, sometimes mid cushioned
  • 8 to 12 mm - current standard for fast training/long distance racing shoes, generally mid cushioned, sometimes highly cushioned
  • 12 mm or more - a common value for normal jogging/running shoes, generally high cushioned.
Measuring the HTTD is quite a simple procedure and can be done in many different ways. Here I will show you my method, that I found being very accurate and reproducible. Only a caliper and a reference frame are needed to complete the measurement.
As showed in Figure 2, after building an L-shaped reference frame, the first operation is to set the caliper to zero.

Figure 2 Setting the caliper to zero.
The first measure to take is the heel pack height (outsole+midsole+insole), as shown in Figure 3. The measurement point is exactly in the lowest area where usually the heel is.

Figure 3 Measuring the heel pack height.
The second and last measure involves the fore foot zone. During this operation you want to be sure that the outsole is touching the reference plane (normally running shoes have a quite strong curvature in this zone). Normally the measurement point is under the metatarsal area, at the centre of the foot.

Figure 4 Measuring the fore foot pack height.
The difference between the first (heel pack) and the second (fore foot pack) measure is the HTTD. Typical results are listed here.

Here you can find a list of my running-related posts. Now shut down the notebook and have a run! 

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