Relationship Between Muscle Activity And Movement Reassessed

For a long time, scientists have believed that they understand animal locomotion and its principles fairly well – the nerves generate a signal to the muscles and their activity causes movement.

galBut a group of researchers at the University of California, Riverside, has found out and showed in their unique study on wild green anole lizards that the relationship between movement and muscle activity is far more complex than could have ever been imagined. The study was published in the British journal Proceedings of the Royal Society B, March 12, 2014.

The aim of the study was to understand the mechanism and peculiarities of animal movement on complex vertical and horizontal surfaces, such as a surface of a tree. As they saw the changes of muscle function, they believed they would record the associated changes of movement. However, their findings prove that such a direct relationship between movement and muscle activity doesn’t always take place.

Many scientists do research on green anole lizards, mostly by removing their muscles and studying them in a lab. Meanwhile, the study by the team at University of California focuses on real-life observations and experiments, where all the measurements are made as the animal is actually moving in its natural habitat.

For the purposes of the research, electrodes were implanted into the limbs of 7 male green anoles to record their movements on various kinds of surfaces (90° slope and flat surface, narrow and broad branches). The visible locomotion was recorded using high-speed video and electromyography was used for simultaneous tracking of electrical muscle activity.

As the scientists changed the properties of the habitat, the lizards adapted their motions, but astonishingly, the equipment showed very little change of muscle activity.

For instance, when the lizards were moving along narrow branches (as opposed to broad branches), the team noticed a significant change of movements, but no considerable change in muscle activity. On the contrary, when the anoles were running up a incline, muscle activity altered while movement basically remained the same.

Timothy Higham, an assistant professor of biology at the University of California, explains that people can’t evaluate muscle function only by what they observe.

The green anole lizards in the experiment are about two inches long and weigh only five grams, but their muscles’ functioning is identical to other vertebrates, meaning that the findings from the study may well be extended to other fields.

The research has raised a number of questions for ecomorphology, for instance, how species’ anatomy is affected by its environment and habitat. Also, the study results may be useful for people designing robots or artificial limbs.

The discrepancy between changes of locomotion and muscle activity indicates there may be some concealed aspects, and it will be necessary to discover and interpret them.

free blog themes