May 2012

Benefits of variable-stiffness footwear may go beyond reducing knee OA risk #6972072

By Jordana Bieze Foster

Variable-stiffness shoes may have performance benefits for athletes in addition to addressing kinetic risk factors for knee osteoarthritis, according to research from the National University of Singapore.

Investigators analyzed 30 participants (16 women) as they walked, ran, and jumped while wearing experimental athletic shoes with variable-stiffness soles or control shoes with uniform sole stiffness. The sole material in the experimental shoes was the same stiffness as the control shoes on the medial side and 1.6 times stiffer on the lateral side. Previous research from Stanford University has demonstrated that this design effectively reduces peak knee adduction moment, which has been associated with severity and progression of medial knee osteoarthritis (see “OA research: It’s all about the shoes”).

Consistent with previous studies, the Singapore investigators found that shoes with variable-stiffness soles were associated with significantly lower external knee adduction moments during walking, running, and jumping compared to the control shoes. However, they also found that the experimental shoes were associated with significantly higher levels of anterior ground reaction force during running, which could have implications for forward propulsion and acceleration, according to Jin Huat Low, a bioengineering student at the university who presented his group’s findings at the i-FAB congress.


Teoh J, Chen W, Lee T. Influence of variable stiffness shoes in sports performance and protection of lower extremity injury. Presented at 3rd International Foot and Ankle Biomechanics Congress, Sydney, April 2012.

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