What Studies Reveal About Torsional Stiffness And Injury Risk In Athletes

In the last couple of blogs, we have talked about the mechanics of shoes. More recently, I have discussed shoe flexion and heel counter stiffness in relation to their ability to control or alter foot mechanics, and whether they have any bearing on overall risk for athletes. Now I would like to turn our attention to torsional stiffness.

Torsional stiffness varies from shoe to shoe and sport to sport. Barefoot type running shoes tend to have minimal torsional stiffness as do wrestling shoes and even some basketball, soccer and football shoes.

For some sports with a lot of side-to-side cutting movements, decreased stiffness can decrease overall injury risk in relation to ankle sprains. In a 2013 study, Graf and Stefanyshyn found that “Increased footwear torsional stiffness causes higher ankle eversion moments which may increase the risk for ankle injuries.”¹ However, as far as the knee was concerned, they found no increased risk for anterior cruciate ligament (ACL) injury from lower torsional stiffness shoes.

In 2012, Graf and Stefanyshyn looked at a shoe’s torsional stiffness effects on patellofemoral pain syndrome (PFPS).² What they found was that with traditional rearfoot strike running patterns, they did not see “any effect on injury risk patterns for PFPS.” They did note that for any movements that were primarily forefoot-related, torsional stiffness could potentially be problematic.

Recently, in 2017, Graf and coworkers looked at torsional stiffness effects on lower limb biomechanics and concluded … “While shoe torsional stiffness influences foot kinematics significantly, it does not affect lower extremity running biomechanics in a way that would alter the risk of running injuries.”³

What does all this mean? It likely means that for non-cutting sports, midfoot shoe stiffness is not that important as the studies show it does not seem to affect overall running mechanics or increase certain knee injury risk. For cutting sports though, a shoe’s midfoot and ankle stiffness can affect injury risk for athletes. It is likely best for most cutting sports to have a shoe that is not overly stiff from a torsional perspective. Stiffer shoes can keep the foot from compensating and force the ankle to invert, which leads to increased ankle sprain risk. For straight line running, not trail running, a shoe’s torsional properties do not seem to make as much of a difference.

References
1.    Graf ES, Stefanyshyn D. The effect of footwear torsional stiffness on lower extremity kinematics and kinetics during lateral cutting movements. J Footwear Science. 2013;5(2):101-109.
2.    Graf ES, Stefanyshyn D. The effect of shoe torsional stiffness on lower extremity kinematics and biomechanical risk factors for patellofemoral pain syndrome during running. J Footwear Science. 2012;4(3):199-206.
3.    Graf ES, Wannop JW, Schlarb H, Stefanyshyn D. Effect of torsional stiffness on biomechanical variables of the lower extremity during running. J Footwear Science. 2017;9(1):1-8.