When our feet land on the ground, we land along the outer side of the foot. This is a supinated position. The degree of this supination varies according to whether we land on the heel or fore-foot, type of arch, lower limb alignment and also pelvic alignment. From that point we pronate from this position. The degree of pronation is also dependent on many factors. For example, a high rigid arch (or supinated foot) will not pronate much or not at all. A flexible high arch will pronate. A flat arch will pronate or over-pronate.
D2D states that he has "virtually flat feet" and that he supinates. I do not know how he comes to this conclusion, or if somebody told him this. Interestingly in an earlier thread D2D mentioned that he wears neutral running shoes. I therefore suspect that he has a flexible arch. However what is categoric is that apart from the initial phase of supination on heel or foot strike, we cannot supinate from a flat arch position. It would have to lift itself off the ground against gravity and inertia.
