Footwear upper panel stiffness does not alter foot gearing during agility drills

Understanding how footwear modifications affect force attenuation in the foot and ankle helps to optimise athletic performance and safety. A stiffer upper panel may reduce metatarsophalangeal (MTP) dorsiflexion creating a stiffer lever and shifting the ground reaction force anteriorly along the foot. This can affect the moment arms about the ankle joint centre from the ground reaction force vector and Achilles tendon, influencing foot gear ratios during dynamic tasks. The gear ratio is a measure of mechanical leverage that relates moment arm lengths to describe output torque in the foot and ankle system. The effect of different footwear modifications on this ratio throughout movement tasks have been investigated, however, research on the upper panel’s influence on foot gearing is limited. This study investigated how upper panel stiffness altered the gear ratio during ground contact in 40 recreationally active participants. Gear ratios and Achilles muscle-tendon velocity (AMTV) were calculated using marker-based motion capture and embedded force plates during three agility tasks (countermovement jump (CMJ), triangle drop step drill (TDS), anterior-posterior drill (AP)) in custom running shoes with increasing upper panel stiffness (soft, moderate, stiff). Statistical parametric mapping (SPM) was used to determine differences in the time-series gear ratio and AMTV. Deceleration was defined from initial contact to the sacral marker’s lowest vertical position, and push-off was from this lowest point to toe-off. No differences in gear ratio and AMTV throughout ground contact existed between footwear conditions in any tasks. These results indicate that gear ratio and AMTV are unaffected by upper panel stiffness.