How Does Manipulation of Advanced Running Shoe Midsole Compliance Influence Frontal Plane Kinematics and Kinetics?

Advanced footwear technology distance running shoes (AFTs) have been shown to reduce the oxygen cost of running at a given speed compared to traditional distance running shoes. This may be at least partly driven by the compliant, resilient midsole properties of AFTs. Increasing the compliance of AFT midsoles may further improve running economy but may also result in increased frontal plane motion and therefore instability. This study quantified frontal plane kinematics and kinetics during running with one type of advanced footwear technology running shoe with three different midsole properties. The three shoe conditions had Asker C compliance values of C-55, C-45 and C-25. Twenty-one male and female runners ran at two speeds in each of the shoe conditions on a force-instrumented treadmill whilst kinematics were synchronously recorded. Frontal plane ground reaction forces and rearfoot, knee and hip kinematics and kinetics were compared between conditions. Peak rearfoot eversion angle and range of motion were not different between footwear conditions, whereas peak eversion velocity was 12% and 17% slower in the most compliant shoe than the control shoe and least compliant shoe respectively. Peak knee and hip adduction range of motion were both lower in the most compliant shoe. Peak lateral ground reaction forces and center of pressure excursion were also lower in the most compliant shoe. The reduced frontal plane motion and forces when running in a shoe with a highly compliant midsole may be influenced by the rapid deformation of the midsole and an increased frontal plane rearfoot joint stiffness.