Meeting Abstract
The bodies of many fishes are very flexible. Flexible bodies may allow them to store and release elastic energy during steady swimming, but they also must accelerate and turn rapidly, behaviors for which a stiffer, stronger body would be better. Clearly fishes are capable of both types of behaviors; how do they balance these conflicting locomotor demands? One strategy fish may use to accelerate more efficiently is to contract muscles on both sides of their bodies to increase their relative stiffness. To determine the muscle activity during impulsive swimming, we implanted bipolar electromyographic electrodes in the superficial red axial muscle of bluegill sunfish (Lepomis macrochirus) and recorded muscle activation during linear accelerations and steady swimming between 0.5-3.0 body lengths/s. In addition, we used a new digital accelerometer that measures three-dimensional acceleration and rotational velocity to quantify the acceleration and 3D orientation of a fish’s body. Linear accelerations resulted in higher amplitude rotations: fish moved their heads from side to side more and increased their tailbeat amplitude when accelerating forward compared to that during steady swimming. Duty cycles (percentage of strain cycle period) increased with swimming velocity. The timing of muscle activity relative to body motion will be discussed. By shifting the timing of muscle activation, fishes with flexible bodies can potentially control their effective body stiffness and enhance the efficiency of both steady and impulsive swimming.
