Meeting Abstract
Muscle Explorer simulates the performance of a simple musculoskeletal system in which a muscle shortens against an elastic element in series with a mass. The model can be used interactively in a web browser to explore a wide range of muscle-tendon behaviors, for example to predict results of in-vitro muscle experiments or the performance of explosive movements such as jumping or striking. The model simulates the interaction of several adjustable elements: a muscle-like actuator, a viscous damper, an inertial muscle mass, a hookean spring, a massless lever with a variable mechanical advantage, and an inertial projectile mass. Output is in graphical and numeric form. To simulate a movement, the physiological and biomechanical parameters of the model are set and the muscle is activated. The muscle builds force that stretches the spring. Recoil of the spring rotates the lever and accelerates the projectile mass. The muscle generates force using realistic force-velocity and force-length properties for vertebrate skeletal muscle, and the physics of the movement are modeled using a fourth-order Runge-Kutta integrator. The muscle consists of three subcomponents: (1) the muscle actuator produces force based on shortening velocity, length, and excitation level, (2) an inertial mass that is accelerated by the balance of actuator and spring forces, and (3) a viscous damper that opposes movement of the mass. The tendon component attached to the muscle component is a hookean tension spring that links the muscle to the appendage and the projectile mass. A latch prevents the lever from rotating as the spring exerts force on the lever; it can be released under specified conditions. The model is implemented in JavaScript, CSS and HTML at http://knot.cas.usf.edu/Musclemodels/muscleexplorer.html and is intended for use in research and teaching.
