2.2.5. Experimental Procedure

• Measurement of the ratio of the foot length and navicular length

In this experiment, the foot length was measured with a foot gauge. The subjects were required to stand evenly, placing one foot on the foot gauge. The heel of the foot was measured to the front position of the foot (great toe or index toe). The protruding position of the navicular bone was found and marked by palpation, then the length from the navicular bone to the front position of the foot was measured by a ruler. After recording, the value was divided by the foot length to obtain the position ratio of the corresponding navicular bone (Figure 5).

**Figure 5.** Illustration of the measurement procedure of the navicular length.

• Ink-type footprint measurement

As an index of determining the foot type in the current study, the measurement and calculation of the ink-type footprint refers to that mentioned in the paper by Cavanagh in 1987 [6,15], where the subjects stand statically with one foot on the ink-type footprint printer that prints the footprint of the subjects. The measurement needs to be repeated if swaying or over-imprint occurs (such as standing with one foot) (Figure 6).

**Figure 6.** Typical example of ink-type footprint diagram.
