Data from: The foot is more than a spring: human foot muscles perform work to adapt to the energetic requirements of locomotion
Riddick, Ryan, University of Queensland
Farris, Dominic J., University of Exeter
Kelly, Luke A., University of Queensland
Published Feb 01, 2019 on Dryad.
Cite this dataset
Riddick, Ryan; Farris, Dominic J.; Kelly, Luke A. (2019). Data from: The foot is more than a spring: human foot muscles perform work to adapt to the energetic requirements of locomotion [Dataset]. Dryad. https://doi.org/10.5061/dryad.j406q83
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 < 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 < 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.
EMG and mechanical work of foot during stepping
September 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.