DOI: 10.5061/dryad.j406q83
title: Data from: The foot is more than a spring: human foot muscles perform work to adapt to the energetic requirements of locomotion

description: The foot has been considered both as an elastic mechanism that increases
 the efficiency of locomotion by recycling energy, as well as an energy
 sink that helps stabilize movement by dissipating energy through contact
 with the ground. We measured the activity of two intrinsic foot muscles,
 Flexor Digitorum Brevis (FDB) and Abductor Hallucis (AH), as well as the
 mechanical work performed by the foot as a whole and at a modelled plantar
 muscle tendon unit (MTU) to test whether these passive mechanics are
 actively controlled during stepping. We found that the underlying passive
 visco-elasticity of the foot is modulated by the muscles of the foot,
 facilitating both dissipation and generation of energy depending on the
 mechanical requirements at the center of mass (COM). Compared to
 level-ground stepping, the foot dissipated and generated an additional
 –0.2 J/kg and 0.10 J/kg (both P &lt; 0.001) when stepping down and up
 a 26 cm step respectively, corresponding to 21 % and 10 % of the
 additional net work performed by the leg on the COM. Of this compensation
 at the foot, the plantar MTU performed 30 % and 89 % the work for step
 downs and step ups respectively. This work occurred early in stance and
 late in stance for stepping down respectively, when the activation levels
 of FDB and AH were increased between 69 % - 410 % compared to level steps
 (all P &lt; 0.001). These findings suggest that the energetic function
 of the foot is actively modulated by the intrinsic foot muscles and may
 play a significant role in movements requiring large changes in net energy
 such as stepping on stairs or inclines, accelerating, decelerating, and
 jumping.
description: EMG and mechanical work
 of foot during steppingSeptember 10 2018 This
 dataset was constructed using Matlab 2017b. The data are organized into
 three structures: 'Down', 'Level', and 'Up'
 which contain the data for the corresponding condition. At the deepest
 level of each structure, the data are organized into matrices where each
 row corresponds to the stance phase data of a single step for a single
 subject. The total number of rows is equal to the number of total steps
 across all subjects for that condition. The number of columns represents
 the average length of stance phase for that condition across all
 participants at a down-sampled rate of 150 Hz. There are two exceptions to
 this format: 1) The field 'StanceTime' is an array in which each
 element is the duration of stance time for each stance time in seconds. 2)
 The field 'Subject' is an integer array where each element
 corresponds to the subject from which the data come from. Moment data are
 normalized by the weight of the participant and are in units of Nm/kg.
 Force data are normalized by the weight of the participant and are in
 units of Nm/kg. Power data are normalized by the weight of the participant
 and are in units of W/kg. EMG data are normalized on a range of 0 to 1
 based on the minimum and maximum EMG recorded during the stance phase of
 all conditions on a per-participant basis. Speed data are in units of m/s.
 Length data are in units of m.FootAsActuator.mat