Midtarsal joint stiffness alters the metabolic cost of simulated running via mechanisms other than changes in foot energy storage and return

Area of Science:

• Biomechanics
• Human locomotion
• Sports science

Background:

• The foot's arch is hypothesized to enhance running metabolic efficiency.
• Understanding the role of foot arch mechanics in running economy is crucial for sports performance and injury prevention.

Purpose of the Study:

• To investigate the effect of midtarsal joint (foot arch) stiffness on the metabolic cost of transport during rearfoot and non-rearfoot strike running.
• To explore the underlying mechanical mechanisms responsible for changes in metabolic cost with varying foot arch stiffness.

Main Methods:

• Computational musculoskeletal simulations were employed to model steady-state running.
• Simulations analyzed rearfoot and non-rearfoot strike gaits across a spectrum of midtarsal joint stiffnesses.
• Metabolic cost of transport and mechanical work at the midtarsal joint were quantified.

Main Results:

• Increasing midtarsal joint stiffness decreased metabolic cost of transport by approximately 5% in rearfoot strike running.
• Conversely, increasing stiffness increased metabolic cost of transport by approximately 11% in non-rearfoot strike running.
• Mechanical work at the midtarsal joint decreased with increasing stiffness in both running conditions, irrespective of the observed metabolic cost changes.

Conclusions:

• Foot arch stiffness has a differential impact on running economy depending on the foot strike pattern.
• The findings suggest that mechanisms beyond passive elastic energy storage and return, such as altered joint work or muscle activation patterns, influence metabolic cost.
• Optimizing foot arch mechanics may be specific to individual running styles for improved metabolic efficiency.