RUI Collaborative: Biomechanics and Control of Landing in Toads

Mount Holyoke College, South Hadley MA

Investigators

Abstract

The hindlimb muscles of frogs and toads have served as an exemplary model for understanding muscle?s role in powering propulsive movements like jumping. Anything that jumps must ultimately land, but unlike during jumping, where muscles produce the energy to accelerate the body, controlled landing requires muscles to dissipate energy to decelerate the body. The role of muscles during energy dissipation remains poorly understood. This research will reveal important principles associated with this locomotor activity. Terrestrial toads are outstanding at landing, using their forelimbs exclusively to decelerate their bodies. The proposed work will use toad landing as a model system for understanding how muscles control forelimb joint movements (shoulder, elbow and wrist) during and after impact. During human jumps, pre-landing activity in leg muscles is used to stiffen joints in preparation for landing, and is tuned to the expected time and magnitude of impact. Recent work demonstrates similarly prescient activity in muscles acting at the elbow joints of hopping toads in mid-air. The proposed work will address the generality of such tuned, pre-landing activity at other forelimb joints, and will specifically test the hypothesis that its utility lies in preventing muscles involved in energy dissipation from stretching to overly long lengths during landing, where injuries are most likely to occur. We will also examine the importance of visual and proprioceptive feedback in helping animals tune muscle activity to coordinate landing after hops of variable height and distance. By integrating biomechanics, muscle physiology and sensory biology this work will highlight fundamental principles governing controlled deceleration, an action common to most locomotor systems. Undergraduate students will be essential to the execution and presentation of this work, and by involving students and faculty from local community colleges, we will broaden direct participation in cutting-edge research.