Abstract
The goal of our study was to explore the mechanical power requirements associated with jumping in yellow-footed rock wallabies and to determine how these requirements are achieved relative to steady-speed hopping mechanics. Whole body power output and limb mechanics were measured in yellow-footed rock wallabies during steady-speed hopping and moving jumps up to a landing ledge 1.0 m high (approximately 3 times the animals' hip height). High-speed video recordings and ground reaction force measurements from a runway-mounted force platform were used to calculate whole body power output and to construct a limb stiffness model to determine whole limb mechanics. The combined mass of the hind limb extensor muscles was used to estimate muscle mass-specific power output. Previous work suggested that a musculoskeletal design that favors elastic energy recovery, like that found in tammar wallabies and kangaroos, may impose constraints on mechanical power generation. Yet rock wallabies regularly make large jumps while maneuvering through their environment. As jumping often requires high power, we hypothesized that yellow-footed rock wallabies would be able to generate substantial amounts of mechanical power. This was confirmed, as we found net extensor muscle power outputs averaged 155 W kg(-1) during steady hopping and 495 W kg(-1) during jumping. The highest net power measured reached nearly 640 W kg(-1). As these values exceed the maximum power-producing capability of vertebrate skeletal muscle, we suggest that back, trunk and tail musculature likely play a substantial role in contributing power during jumping. Inclusion of this musculature yields a maximum power output estimate of 452 W kg(-1) muscle. Similar to human high-jumpers, rock wallabies use a moderate approach speed and relatively shallow leg angle of attack (45-55 degrees) during jumps. Additionally, initial leg stiffness increases nearly twofold from steady hopping to jumping, facilitating the transfer of horizontal kinetic energy into vertical kinetic energy. Time of contact is maintained during jumping by a substantial extension of the leg, which keeps the foot in contact with the ground.
Highlights
In an uneven and unpredictable world, many terrestrial animals that utilize energy-saving mechanisms while moving at steady speed are confronted with the need to generate substantial mechanical power to accelerate or jump in order to avoid an obstacle, negotiate uneven terrain, or evade a predator
The aim of this study was to explore the differences in whole-body mechanics associated with steady-speed hopping vs moving jumps in yellow-footed rock wallabies Petrogale xanthopus L. by means of force plate and high-speed video analysis
The goal of our study was to explore the mechanical power requirements associated with jumping in yellow-footed rock wallabies and to determine how these requirements are achieved relative to steady-speed hopping mechanics
Summary
In an uneven and unpredictable world, many terrestrial animals that utilize energy-saving mechanisms while moving at steady speed are confronted with the need to generate substantial mechanical power to accelerate or jump in order to avoid an obstacle, negotiate uneven terrain, or evade a predator. During steady locomotion over level ground, animals employ various mechanisms to minimize the energy required to maintain a constant speed At faster speeds this is often characterized by a bouncing gait, such as running, trotting or hopping, in which animals may use compliant structures to store and return elastic strain energy during the stance phase of a stride (Cavagna, 1977; Heglund, 1982). Excellent examples of this are large macropod marsupials (kangaroos and wallabies), which are able to store and recover as much as 35% of the mechanical energy of a single hop in their ankle extensor tendons alone (Alexander and Vernon, 1975; Ker et al, 1986; Biewener and Baudinette, 1995). While much work has contributed to understanding the mechanics of energysaving mechanisms during steady-speed locomotion, only
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
