DOI: 10.5061/dryad.866t1g1vt
title: Data for: Mobility of the human foot's medial arch helps enables upright bipedal locomotion

description: Developing the ability to habitually walk and run upright on two feet is
 one of the most significant transformations to have occurred in human
 evolution. Many musculoskeletal adaptations enabled bipedal locomotion,
 including dramatic structural changes to the foot and, in particular, the
 evolution of an elevated medial arch. The foot’s arched structure has
 previously been assumed to play a central role in directly propelling the
 center of mass forward and upward through leverage about the toes and a
 spring-like energy recoil. However, it is unclear whether or how the
 plantarflexion mobility and height of the medial arch support its
 propulsive lever function. Here we show, using high-speed biplanar x-ray,
 that regardless of intraspecific differences in medial arch height, arch
 recoil enables a longer contact time and favorable propulsive conditions
 at the ankle for walking upright on an extended leg. This mechanism may
 have helped drive the evolution of the longitudinal arch after our last
 common ancestor with chimpanzees, who lack this plantarflexion mobility
 during push-off. We discovered that the generally overlooked
 navicular-medial cuneiform joint is primarily responsible for arch recoil
 in human arches, suggesting that future morphological investigations of
 this joint will provide new interpretations of the fossil record. Our work
 further suggests that enabling longitudinal arch recoil in footwear and
 surgical interventions may be critical for maintaining the ankle’s natural
 propulsive ability.
description: This dataset supports the conclusions from the manuscript
 "Mobility of the human foot’s medial arch helps enable upright
 bipedal locomotion". All methods are described in
 the article. <strong>Description
 of the data and file structure</strong>
 Biplanar videoradiography motion for the tibia (tib), talus
 (tal), calcaneus (cal), navicular (nav), medial cuneiform (cmm), first
 metatarsal (mt1) and first proximal phalanx (ph1) are provided between
 maximum arch flattening and maximum metatarsophalangeal joint
 dorsiflexion. The transforms moving the provided bone meshes (in
 boneStruct) from CT space to x-ray space (dataStruct().Tx) for each frame
 of motion (captured at 125 Hz for walking and 250Hz for running) are
 provided, in addition to the modelled transforms for the rigid arch
 (dataStruct().Tx_fix) and simulated tibia positions
 (dataStruct().Tx_fix.tib_at_takeoff and
 dataStruct().Tx_fix.tib_sim_rigidarch_takeoff). The translation component
 is in millimeters. The last section of the included code
 (Arch_Recoil_Example_Plots.m) demonstrates how to plot the bones using
 each transform using the provided function (visualizeBone.m). 
 Joint angles for the medial arch joints (dataStruct().angles) and
 the talar centroid positions (dataStruct().talar_centroid) are included
 (in millimeters). Angles are the first Tait-Bryan rotation  that
 prioritizes dorsi/plantarflexion in degrees. The angles are all distal
 joints relative to proximal. The convention for naming is
 [angle]_[proximal][distal] i.e. DP_calmet represents the motion of the
 first metatarsal relative to the calcaneus in dorsiflexion/plantarflexion,
 where dorsiflexion is positive. Note that the angles are not normalized
 relative to any posture. Instead, the magnitudes describe the anatomy of
 the participant. For example, the participant with the highest arch
 (PRFC012) has an arch angle (DP_calmet) starting at -54 deg. This
 indicates a higher initial starting posture from the bony anatomy than the
 subject with the lowest arch (PRFC016) who starts at -23 deg. The unloaded
 arch angle is stored in the subject structure (subjStruct). See below for
 more details. The corresponding frames of stance
 (dataStruct().stance_frames) indicate each frame's corresponding % of
 stance to facilitate plotting as a function of % stance. 
 Key frames in gait are provided for each trial. The maximum arch
 flattening (dataStruct().keyFrames.max_archFlat) is the time in stance of
 peak dorsiflexion of the metatarsal relative to the calcaneus. The maximum
 metatarsophalngeal joint dorsiflexion angle is used to standardize across
 participants (dataStruct().keyFrames.max_mtpDP). The case where the rigid
 arch is moved with the tibiotalar joint in the takeoff position
 (dataStruct().Tx_fix.tib_at_takeoff) is best matched with the measured
 mobile arch's takeoff position is in
 dataStruct().keyFrames.match_tib. The frame indicating the beginning of
 propulsion as a function of the anterior ground reaction force becoming
 positive is given in
 dataStruct().keyFrames.anteriorGRFPropulsion. The
 centre of mass position during the stride (in meters) is provided between
 the beginning of propulsion, as defined by the first frame when the
 anterior-posterior ground reaction force becomes positive, and maximum
 metatarsophalangeal joint dorsiflexion.  The subjStruct
 contains the anonymized subject demographic information. Height is in
 metres and weight is in kilograms. The subject bone meshes are provided
 and are stored in CT space. They can be plotted using the bone points and
 connections (all 1 based). See the last section of the provided code for
 an example. Coordinate systems are provided in the subjStruct under the
 bones sub structure. For example, for the tibia,
 subjStruct().bones.tib.T_inertial  provides the 4x4 inertial coordinate
 system for the tibia in CT space.  [...].T_long axis provides the
 coordinate system that is biased to align the z-axis with the tibial
 shaft, which is used to align the tibia in the simulated take-off
 positions in gait. [...].T_TC is aligned based on a cylinder fit to the
 talocrural surface on the tibia to describe talocrural dorsiflexion as a
 function of the joint surface. A similar coordinate system is given in the
 talus bone information : subjStruct().bones.tal.T_TC is made similarly,
 with a cylinder fit to the talar dome (the talar component of the
 talocrural joint).  The subjStruct also contains the
 unloaded arch dorsiflexion angle between the calcaneus and the metatarsal
 in degrees.  The tibLeanStruct contains the chimpanzee
 and human tibial lean data. tibLeanStruct.human has both the mobile and
 rigid arch tibia lean angles relative to the vertical axis in degrees for
 each motion frame (dataStruct().COM.anterior and .superior).  The human
 data corresponds to the data in the dataStruct. The chimpanzee data has
 been normalized to 101 points of the gait cycle. The
 provided code (Arch_Recoil_Example_Plots.m) uses this data to recreate the
 base plots in the manuscript. Run the code with the arch_recoil_data.mat
 on the path. All plots should generate automatically. Please contact
 Lauren Welte at l.welte@queensu.ca if you encounter any issues.
  
description: MATLAB is required to use these files. Please contact the
 corresponding author if you are interested in the data in an alternative
 format.