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

Area of Science:

• Biomechanics
• Sports Medicine
• Footwear Engineering

Background:

• Advanced footwear technology running shoes (AFTs) can improve running economy by reducing oxygen cost.
• Midsole compliance is a key factor in AFTs, potentially enhancing performance but also affecting stability.
• Understanding the impact of midsole properties on running biomechanics is crucial for footwear design.

Purpose of the Study:

• To quantify frontal plane kinematics and kinetics during running with AFTs featuring varying midsole compliances.
• To investigate the relationship between midsole compliance and running instability.
• To compare frontal plane ground reaction forces and joint motion across different footwear conditions.

Main Methods:

• Twenty-one runners ran at two speeds on a force-instrumented treadmill.
• Kinematic data were synchronously recorded while runners used AFTs with three midsole compliance values (Asker C: C-55, C-45, C-25).
• Frontal plane ground reaction forces, rearfoot, knee, and hip kinematics, and kinetics were analyzed.

Main Results:

• Peak rearfoot eversion velocity was slower in the most compliant shoe.
• The most compliant shoe condition showed reduced peak knee and hip adduction range of motion.
• Peak lateral ground reaction forces and center of pressure excursion were lower with increased midsole compliance.

Conclusions:

• Highly compliant midsoles in advanced footwear may reduce frontal plane motion and forces during running.
• This effect might be due to rapid midsole deformation and increased frontal plane rearfoot joint stiffness.
• Further research can optimize AFT design for both performance and stability.