Nonergonomic! Lateral Stability in Sideward Cutting Movements
Lateral Stability in Sideward Cutting Movements
With respect to leverage, the barefoot situation has an advantage over the shod situation. The shoe sole increases the lever arm and as a consequence the moment about the subtalar joint. (emphasis added)
All other shoes had one result in common: torsion increased from touchdown to maximum, which, given similar forefoot angles, is equivalent to an inversion moment of the rearfoot relative to the forefoot. Such a movement is not welcomed to improve the lateral stability.
When looking at the forefoot, there are two different landing techniques that can be observed. Barefooted "the flat-foot approach" is chosen by lowering the metatarsals parallel to the ground. With shoes the medial border of the forefoot touches the ground first causing a forefoot angle of around 20%. Within a time span of 40 ms the forefoot is then lowered toward the ground thereby rolling over the medial border of the shoe sole. In other words, a "rolling approach" can be observed with shoes.
Inversion is mostly reduced in the barefoot condition.
The best lateral stability can be observed in the barefoot condition.
Ironically, many shoes loudly touted as "ergonomic" feature ludicrously wide soles, supposedly to offer "lateral stability." The "ergonomic" shoe designers apparently imagine shoe soles that flare out like horses' hooves provide human feet with greater stability. But human beings are not horses, human legs are not horses' legs, and human feet are not horses' hooves. Human locomotion is far too different from equine locomotion for the latter to be applicable to human shoe design. As Stacoff, Steger, Stussi and Reinschmidt note, "The shoe sole increases the lever arm and as a consequence the moment about the subtalar joint." The net result is not more, but less stability as the sole of the foot is artificially wrenched from its natural (and correct) position. Once more, the Law of Unintended Consequences asserts itself, seriously discrediting the "ergonomic designers'" simplistic understanding of human anatomy.
-- Bevin Chu
Explanation: Lateral Stability in Sideward Cutting Movements
Illustration(s): Unnaturally Wide "Ergonomic" Soles
Author(s): Alex Stacoff, Jurg Steger, Edgar Stussi, and Christoph Reinschmidt
Affiliation: "Lateral stability in sideward cutting movements," Medicine and Science in Sports and Exercise, 28(3), 1996, pp. 350-358.
Publication Date: April 11, 1997
Original Language: English
Editor: Bevin Chu, Registered Architect