Accessible Summary:

Purpose: The purpose of this experiment was to improve footwear in terms of balance and impact control while retaining comfort.  Footwear cause instability results from to attenuation of tactile sensibility because the sole of the shoe attenuates localized plantar deformations and plantar skin shear stress - adequate stimuli for SA II mechanoreceptors of the plantar skin. Within the constraint on stability imposed by footwear, there is extreme variability in stability. While wearing footwear, humans rely on less precise muscle and tendon receptors for foot position judgements. These receptors are influenced by "after-effects" - persistent discharge that occurs particularly with medial-lateral oscillation of the foot in the frontal plane caused by footwear. Footwear design greatly influence these after-effects, which accounts for the variability in footwear stability and hence impact with their use  since excessive impact has been shown to be a behavioral response to loss of stability.  The hypothesis tested in this report is that sole material that compresses but recover pre-compression thickness slowly would dampen foot oscillatory movements in the medial-lateral plane thereby minimizing after-effects. It is hoped that this would improved stability compared to footwear without these properties. The result would be improved foot position awareness, improved balance, lower impact while retaining comfort.

Synopsis:   Balance was inferred by sway measures using a force platform. Comfort was estimated using a rating scale.  Materials were examined that differed in the recovery to pre-compression thickness in 1 second.  I was found that thin sole material of similar softness of current shoe insoles and midsoles, yet much lower in resiliency - allowing only 5% recovery in 1 second, provided superior balance, and equal comfort to high resiliency materials. Stability with the use of these interfaces was similar to the barefoot condition. 

Significance:  Previous reports indicated that thin soles made of harder material would improve balance, and consequently lower impact somewhat at the expense of comfort.  This report indicates that a thin layer of extremely low resiliency sole material is an effective means of  improving stability while wearing footwear to levels previously unobtainable while retaining the comfort typically associated with shoes with traditional thick-high resiliency sole material that destabilize, such as those used in athletic footwear.