This dataset contains experimental data, musculoskeletal simulation outputs, and analysis code supporting: Leeuwis et al., 2026 “The energetic cost of human standing balance and gait initiation over a range of natural postures.” Experiment 1: Quiet standing energetics Includes motion capture, ground reaction forces, electromyography, metabolic analyzer data, and OpenSim simulations. Experiment 2: Gait initiation energetics Includes motion capture, ground reaction forces, OpenSim simulations, and derived energetic estimates. The repository contains the participant-averages used for statistical analysis in the manuscript, code for the reproduction of all figures, and provides time-synchronized timeseries data for all measurement systems.

MATLAB, 2023a

OpenSim, version 4.3

Participant means per condition for important variables are provided in the "Statistics" folder within Experiment 1 and 2, respectively (.csv). The README file for each experiments lists the unit and definition of each MATLAB variable. These .csv files can be loaded in JASP to replicate statistical analyses performed for the paper. Alternatively, we provide all raw, trial-synchronized, data for both experiments in a MATLAB table (.mat) for each participant separately. Running "main_Experiment1" and "main_Experiment2" in MATLAB loads all the experimental trials into the workspace into a table called "Epochs" and plots all figures that are in the manuscript or supplementary material. The Epochs table is a single MATLAB table, where each row corresponds to a trial. This table contains columns corresponding to the subject number, condition, and other metrics. The following MATLAB tables are stored within this row containing the timeseries data of that trial. The time vector "t" in each table is synchronized to the start of that trial. - T_trajectories: labelled motion capture trajectories of all markers (see S1 Appendix of manuscript for marker name definitions), - T_analog: analog EMG data (Experiment 1) and synchronization trigger used to align trials, - T_qtm: additional information from Qualisys Track Manager, including force plate data and center of pressure, - T_cosmed: breath-by-breath metabolic analyzer data (Experiment 1) with timestamps synchronized to the other systems. Variables are as recorded by the COSMED K5 manual, with the addition of the converted energy expenditure "P" in W and "Pkg" in W/kg. All relevant data was also converted to file formats that can be natively loaded into Opensim. All models, input data, and simulation results are provided in the following structured folders: 0 - Models, with the unscaled and scaled models for all participants (.osim), 1 - OpenSim marker (.trc) and ground reaction force (.mot) data, including an external loads (.xml) file required to couple the ground reaction force data to body segments of the model during simulations, 2 - Scale, with the settings used to generate scaled models (.xml), 3 - IK, with inverse kinematics settings (.xml) and results (.mot), 4 - ID, with inverse dynamics settings (.xml) and results (.mot), 6 - SO Uhlrich, with static optimization results of activations (.csv and .sto), fiber/tendon length, force, and velocity (.csv), and generalized forces (.sto), 7 - Analyze, with output of the analyze step, providing body kinematics of position, velocity, and acceleration (.sto). Code is provided to load an .sto file into MATLAB ("loadStoToTable.m") and to re-run all OpenSim analyses if desired ("run_OpenSim_analyses_ExperimentX.m"). The analyses require: - MATLAB (tested on version 2023a) - OpenSim (for rerunning OpenSim analyses only, tested on version 4.3) - MATLAB Static Optimization code by Uhlrich et al. 2022 (included in repository, for rerunning OpenSim SO analyses only) All participants provided signed informed consent to publish their raw data under a CC-BY license.