Motors and Dampers: The Energetic Tradeoffs in the Shod Foot With Increasing Walking Velocity.

backgroundThe dual influences of velocity and footwear on ankle-foot energetics are particularly relevant for clinical populations who rely on footwear during ambulation. Although walking velocity influences energetic demands of foot structures, footwear may modify these relationships by restricting joint motion. This study aimed to characterize ankle-foot energetics while participants walked at a wide range of velocities while wearing supportive shoes.

methodsEighteen healthy participants walked at four height-normalized velocities (0.4-1.0 statures/second) in supportive footwear while kinematic and kinetic data were collected. Ankle, midtarsal, and metatarsophalangeal (MTP) work was quantified and compared using repeated-measures ANOVAs with Holm pairwise tests.

resultsMTP positive and negative work increased with shod walking velocity, though negative work increased substantially more than positive work. Midtarsal positive work also increased while maintaining minimal negative work across all velocities. Ankle positive work significantly increased with velocity accompanied by small but significant increases in negative work.

conclusionsAt all velocities, the MTP joint functioned as a mechanical damper and its damping characteristics became more pronounced as velocity increased. The midtarsal joint functioned as a strut, with a small motor role which became more prominent as velocity increased. The ankle had mixed roles, primarily between strut and spring, with a small damper/motor role that traded off with velocity (less damper more motor as velocity increased). The presence of supportive footwear attenuated positive and negative work across velocities when compared to previous barefoot studies, with the largest difference in the midtarsal's negative work, suggesting footwear substantially modifies natural foot mechanics through increasing velocities.