Dynamic angular stiffness about the metatarsophalangeal joint increases with running speed.

Area of Science:

• Biomechanics
• Sports Science
• Footwear Engineering

Background:

• Footwear longitudinal bending stiffness influences metatarsophalangeal (MTP) joint mechanics.
• Optimal footwear bending stiffness for running performance is under investigation.
• The effect of running speed on optimal bending stiffness is largely unknown.

Purpose of the Study:

• To investigate dynamic angular stiffness of the MTP joint across various running speeds.
• To understand how MTP joint mechanics adapt to different running velocities.

Main Methods:

• Eighteen participants ran at five distinct speeds (3.89–6.11 m/s).
• MTP joint angles, moments, and stiffness were estimated for each speed.
• Defined active stiffness, critical stiffness, and instantaneous MTP joint stiffness.

Main Results:

• Running speed significantly affected critical stiffness, maximum MTP moment, MTP moment at maximum dorsiflexion, and MTP range of motion.
• Active stiffness showed no significant change with running speed.
• The foot significantly contributes to MTP joint torque and stiffness, appearing to dominate the foot-shoe complex.

Conclusions:

• MTP joint involvement increases with running speed.
• Foot-shoe complex stiffness is time-dependent, fluctuating during the stance phase.
• Footwear design for performance should consider speed-dependent MTP joint mechanics and the foot's dominant role in stiffness.