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.

Figure 3 Measuring the heel pack height.

Figure 4 Measuring the fore foot pack height.