A biomechanical evaluation of sorbothane

Area of Science:

• Orthopedic biomechanics
• Materials science

Background:

• Sorbothane is a viscoelastic polymer used in orthotic insoles.
• It's claimed to absorb 95% of foot strike impact energy.
• Its use aims to reduce symptoms from joint degeneration and soft tissue disorders.

Purpose of the Study:

• To investigate the viscoelastic properties of Sorbothane.
• To substantiate or refute claims of high impact energy absorption.
• To determine the actual impact reduction in foot strike scenarios.

Main Methods:

• Durometer tests at various temperatures.
• Compression tests on Sorbothane discs with varying lateral constraints and loading rates.
• Analysis of material properties under simulated foot strike conditions.

Main Results:

• Sorbothane exhibits viscoelastic solid characteristics with a two-second relaxation time.
• Lateral constraint significantly affects material properties when bonded.
• Final transmitted stress reduction during foot strike was limited to approximately 10%.

Conclusions:

• The impact absorption capacity of Sorbothane is significantly less than widely claimed.
• The material's properties are influenced by its integration into insoles.
• While offering some therapeutic benefit, the impact reduction is not as substantial as suggested by previous authors.