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

The foot’s arch has been proposed to aid in metabolically efficient running. Computational musculoskeletal simulations of steady state rearfoot and non-rearfoot strike running across a range of midtarsal joint (i.e. foot arch) stiffnesses indicated that with increasing stiffness the metabolic cost of transport decreased by ∼5% in rearfoot strike running but increased by ∼11% in non-rearfoot strike running. The magnitude of mechanical work performed about the midtarsal joint as its stiffness increased followed a similar decreasing pattern in both running foot strike conditions, suggesting that mechanisms beyond foot energy storage and return were responsible for the altering metabolic cost.