Abstract

Full, R.J. 1989. Mechanics and energetics of terrestrial locomotion: From bipeds to polypeds. In Energy Transformation in Cells and Animals. (ed. W. Wieser and E. Gnaiger). Thieme, Stuttgart. pp. 175-182.

Introduction

Animals using legs for terrestrial locomotion show remarkable variation in form and funcuon. Nevertheless, each variation must allow for the repeated generation of the necessary propulsive forces. Obviously, the properlies of musculo-skeletal systems can only allow movement in a certain range of forces, velocities and displacements. Nearly all employ a jointed framework skeleton and striated muscle as levers to power movement.

Studies on humans, other mammals, birds and some lower vertebrates have addressed many critical questions concerning terrestrial locomotion (Alexander and Goldspink, 1977; Pedley, 1977; Heglund et al., 1982). The success of these studies has largely come from exploiting extremes in function that result from differences in body size, not body form. As a direct restfit of these and other studies, our understanding of vertebrate eriestrial locomotion has advanced considerably. Specific hypotheses have been generated concerning mechanical energy fluctuations (Cavagna el al., 1977; Fedak, et al., 1982; Heglund et al., 198a,b), metabolic energy costs (Bennett, 1982; Taylor et al., 1982; Taylor el al., 1980), and stresses in muscle (Biewener et al, 1988; Taylor, 1985) and bone (Biewener, 1983). Moreover, useful mechanic. a] models have been developed (see Blickhan, this volume; McMahon, 1985).

We have focused on variation in Iocomotor design to test whether or not legged locomolion is based on common design principles. Nowhere is there greater diversity in Iocomotor design than in the arthropods. Arthropods have evolved an extraordinary array of structures used to move on land (Hefreid, 1981). They possess different numbers of walking legs (4 in a hermit crab to over 180 in a millipede), a variety of leg lengths and positions, numerous stepping patterns, different musculo-skeletal arrangements, a range of body shapes (long in mi1lipedes and round in some crabs), different styles of locomotion (forwards versus sideways travel) and different oxygen transport systems (gills versus trachea).

Despite vanations in structure, our past measurements of the metabolic cost of locomotion show a remarkable similarity among different arthropods and between arthropods and vertebrates, suggesting the possibflity of underlying pnnciples (Full, 1987; Full, and Herreid, 1983; Full and Herreid, 1984; Herreid, and Full, 1984; Herreid, and Full, 1985; Herreid et al., 1981). Our investigation of ghost crab locomotion examined locomotion mechanics as well as metabolic cost (Blickban and Full, 1987; Full, 1987). This was the first complete study relating arthropod metabolic energetics to the mechanics of terrestrial locomotion. The results were surprising. Similarities in whole animal energetics and mechanics exist between crabs and vertebrates. Our most recent studies of cockroaches provide further evidence for common principles.