OpenSim Tutorial #1
Introduction to Musculoskeletal Modeling
Scott Delp, Allison Arnold, Samuel Hamner
Neuromuscular Biomechanics Laboratory
Stanford University
I. OBJECTIVES
Introduction to OpenSim
Models of the musculoskeletal system enable one to study neuromuscular coordination, analyze
athletic performance, and estimate musculoskeletal loads. OpenSim is open-source software that
allows users to develop, analyze, and visualize models of the musculoskeletal system, and to
generate dynamic simulations of movement [1]. In OpenSim, a musculoskeletal model consists
of rigid body segments connected by joints. Muscles span these joints and generate forces and
movement. Once a musculoskeletal model is created, OpenSim enables users to study the effects
of musculoskeletal geometry, joint kinematics, and muscle-tendon properties on the forces and
joint moments that the muscles can produce. With OpenSim, our goal is to provide a framework
that allows the biomechanics community to create, share, and extend a library of models and
dynamic simulation tools.
Purpose
The purpose of this tutorial is to introduce users to OpenSim by demonstrating the utility of
graphics-based musculoskeletal modeling and illustrating how muscle-tendon lengths and
moment arms depend upon limb configuration. In this tutorial, you will:
• Become familiar with OpenSim’s graphical user interface (GUI)
• Discover some limitations of musculoskeletal models
• Explore differences between “1-joint” (uni-articular) and “2-joint” (bi-articular) muscles
• Use OpenSim to address an important clinical problem
Format
Each section of the tutorial guides you through certain tools within OpenSim’s GUI and asks you
to answer a few questions. The menu titles and option names you must select and any
commands you must type to run OpenSim will appear in bold face. The questions can be
answered based on information from OpenSim and basic knowledge of the human
musculoskeletal system. As you complete each section of the tutorial, feel free to explore
OpenSim and the lower extremity model further on your own. Depending on the amount of
exploration you do, this tutorial will take about 1-2 hours to complete.