This is the part of the shoe that comes in contact with the ground. It is often made of rubber and provides for traction and some degree of shock absorption. It can be sewn, cemented or integrated with the midsole.
Remember that the heel strikes the ground at approximately a 16° angle, lateral from the center of the heel.The force is then transmitted from the sole of the shoe, up the lateral column of the foot and across to the first metatarsal for propulsion (add link see mondays post here for more on progressional forces).This can be assisted by a “rocker” which is a “drop” put into the front portion of a shoe, to ease walking and assist in toe off (more on this in another post).
A flare to the sole of the shoe (usually at the rear, medial or lateral), can be important for stability on uneven surfaces, by providing a bigger “footprint” or surface area contacting the ground (much like Dr Allen’s new Dodge truck).A lateral flare provides extra stability upon heel strike by preventing too much inversion of the heel, but it speeds up the rate of pronation.A medial flare would slow pronation (not great for a supinator though, or folks who keep weight on the outside of the foot for extended periods of time). This flare’s placement (whether medial or lateral) will profoundly affect forces at the mid tarsal joint as the foot comes through mid stance.
The Gait Guys. Making you more “shoeliterate” each day!