Key principle of the efficient running, swimming, and flying

TL;DR

This paper uncovers unifying physical principles underlying efficient locomotion across animals, birds, and fish, based on the variational principle of minimum action and mechanical similarity, explaining speed regulation and body tuning.

Contribution

It introduces a unified physical framework for understanding locomotion in animals, linking muscular and elastic properties through the principle of minimum action.

Findings

Universal intrinsic muscular pressure maintains optimal speeds.

Maximal speeds relate to constant mass-dependent muscle stiffness.

Animals' appendages are tuned to natural frequencies for efficient movement.

Abstract

Empirical observations indicate striking similarities among locomotion in terrestrial animals, birds, and fish, but unifying physical grounds are lacking. When applied to efficient locomotion, the analytical mechanics principle of minimum action yields two patterns of mechanical similarity via two explicit spatiotemporal coherent states. In steady locomotory modes, the slow muscles determining maximal optimum speeds maintain universal intrinsic muscular pressure. Otherwise, maximal speeds are due to constant mass-dependent stiffness of fast muscles generating a uniform force field, exceeding gravitation. Being coherent in displacements, velocities and forces, the body appendages of animals are tuned to natural propagation frequency through the state-dependent elastic muscle moduli. Key words: variational principle of minimum action (04.20.Fy), locomotion (87.19.ru), biomechanics (87.85.G-).