MuscleMimic Models

Oneline install:

pip install musclemimic-models

Musclemimic_models is part of the MuscleMimic research project, in which we created physiologically realistic, muscle-driven musculoskeletal models built on top of MyoSuite. This repository is designed to provide users with two musculoskeletal models: BimanualMuscle and MyoFullBody, that could be used together or independently from the Musclemimic pipeline.

MyoFullBody enables realistic full-body motion control with pure muscle actuation. Below are example fullbody motions demonstrating the model's capabilities, all policies were trained with MuscleMimic.

Backwards Walking KIT_12_WalkingStraightBackwards04_poses.mp4	Walking Running KIT_3_walking_run05_poses.mp4
Walking Turning KIT_4_WalkInClockwiseCircle01_poses.mp4	Dancing Dancing_waltz.mp4

MyoFullbody also allows accurate kinematics when trained with MuscleMimic on AMASS data

BimanualMuscle focuses on upper-limb musculoskeletal control, enabling faster training convergence while preserving full finger articulation capabilities. (The videos shown below were recorded with finger actuation disabled)

Lifting Box Lift_Box_Bimanual.mp4	Waving Wave_Bimanual.mp4
Drinking Water Drinking_Bimanual.mp4	Jumpingjack Jumpingjack_Bimanual.mp4

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Musculoskeletal Models

Both musculoskeletal models are built on MyoSuite components, combining MyoArm, MyoLegs, and MyoTorso models with Hill-type muscle actuators in MuJoCo. This enables studying motor control at the neuromuscular level and realistic muscle output, rather than via idealized joint torque controllers.

Environment Summary

Model	Type	Joints	DoF	Muscles	Focus
BimanualMuscle	Fixed-base	76 (36*)	126 (64*)	54 (14*)	Upper-body manipulation
MyoFullBody	Free-root	123 (83*)	416 (354*)	72 (32*)	Locomotion and manipulation

$^*$ denotes configurations with finger muscles temporarily disabled.

BimanualMuscle Environment

The BimanualMuscle environment is designed for upper-body manipulation task. Explicit contacts are enabled in between both arms and with the thorax.

MyoFullBody Environment

The MyoFullBody environment provides a comprehensive full-body musculoskeletal system with full biomechanical detail and rich contact dynamics, suitable for locomotion, manipulation, and whole-body imitation. We explicitly enable additional collision pairs, such as leg–leg, arm–leg, foot-foot, to capture the required self-contact behavior, including bimanual interactions.

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Getting Started

Prerequisites

The minimum required MuJoCo version for both models is mujoco==3.2.1. To use spec with the main Musclemimic environment, please use mujoco>=3.3.0.

Overview

The structure of the Musclemimic model is as follows. We use MyoFullBody as an example.

musclemimic_models/
└── model/
    ├── arm/
    │   ├── assets/
    │   └── myoarm_bimanual.xml
    ├── body/
    │   └── myofullbody.xml
    ├── head/
    │   └── assets/
    ├── leg/
    │   └── assets/
    ├── torso/
    │   └── assets/
    ├── meshes/
    └── scene/
└── tests/

• assets/ : includes both the kinematics chain files and the assets definition files for each body segment that its under.
• meshes/ : shared mesh files used across models for bones and skulls
• scene/ : MJCF “scene” files used in both MSK as backgrounds
• arm/, body/, head/, leg/, torso/ : model components and their associated assets/
• *.xml : MJCF model definition(s) (e.g., myofullbody.xml, myoarm_bimanual.xml)
• test/: testing files for symmetry between bodies, geoms, sites and muscle

Usage

Via Pypi

Install:

pip install musclemimic-models

Via git clone

Clone and install editable (recommended for development):

git clone https://github.com/amathislab/musclemimic_models.git
cd musclemimic_models
pip install -e .

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MSK Model Refinement and Validation

Muscle Jump and Symmetry

While building MyoFullBody and BimanualMuscle, we corrected left–right limb asymmetries and addressed several unexpected muscle-jumping behaviors. A few representative fixes are shown below.

Muscle Validation

We also cross-validate the current model using previously published cadaver studies and MRI data. A few illustrative examples are included here.

License

This project is licensed under the Apache License. See the LICENSE and NOTICE files for details.

Citation

If you use MuscleMimic in your research, please cite:

@article{li2026musclemimic,
  title={Towards Embodied AI with MuscleMimic: Unlocking full-body musculoskeletal motor learning at scale},
  author={Li, Chengkun and Wang, Cheryl and Ziliotto, Bianca and Simos, Merkourios and Durandau, Guillaume and Mathis, Alexander},
  year={2026}
}

Acknowledgements

The models in this repository build upon MyoSuite, an open-source musculoskeletal simulation framework.