PNAS publishes work by Avis Cohen, Eric Tytell and colleagues

A new article by Professor Avis Cohen (Biology/ISR) and her colleagues Eric D. Tytell, Chia-Yu Hsub, Thelma L. Williams and Lisa J. Fauci has been published in the Proceedings of the National Academy of Sciences of the United States of America.

"Interactions Between Internal Forces, Body Stiffness, and Fluid Environment in a Neuromechanical Model of Lamprey Swimming" examines the roles of body stiffness, muscle activation, and fluid environment for swimming animals, and develops a computational model of a lamprey. The model uses an immersed boundary framework that fully couples the Navier–Stokes equations of fluid dynamics with an actuated, elastic body model. This is the first model at a Reynolds number appropriate for a swimming fish that captures the complete fluid-structure interaction, in which the body deforms according to both internal muscular forces and external fluid forces.

Results indicate that identical muscle activation patterns can produce different kinematics depending on body stiffness, and the optimal value of stiffness for maximum acceleration is different from that for maximum steady swimming speed. Additionally, negative muscle work, observed in many fishes, emerges at higher tail beat frequencies without sensory input and may contribute to energy efficiency. Swimming fishes that can tune their body stiffness by appropriately timed muscle contractions may therefore be able to optimize the passive dynamics of their bodies to maximize peak acceleration or swimming speed.

The research holds significant promise for the development of prosthetics that could aid people with spinal cord injuries. It also has applications for robotics.

Read the article online at the Proceedings of the National Academy of Sciences website.

Published November 4, 2010