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Tammar wallaby / Michelle Bar.. / License
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Tammar wallaby / Michelle Bar.. / License
The tendons of tammar wallaby legs use energy efficiently by taking advantage of elastic energy storage.
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- Amplification strategy for kinetic energy
- Machines that capture energy to use in other applications
- Pumps that recapture input energy
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[Collapse all sections] Summary
Although most animals running across the ground exhibit an
increase in energy cost as their speed increases, the hopping tammar wallaby
can go faster without it costing more energy. Furthermore the female can carry
the heavy load of the infant ‘joey’ in her pouch without increasing her cost of
locomotion. These remarkable feats are due to the use of elastic energy storage
in the large tendons of its hind legs. During the leaping phase of the hop
cycle, the wallaby’s forward movement represents a kinetic energy, and the
gravitational pull back to the ground during the leaping phase is a form of
potential energy. These energies transform into the elastic strain energy of
stretching tendons (such as the gastrocnemius, plantaris, and extensor
digitorum longus) when the foot hits the ground. That energy can then be
recovered in the elastic recoil of those tendons that helps propel the wallaby
back off the ground. As much as 90% of the energy stored in this elasticity can
be recovered for such reuse. The faster the wallaby goes and the heavier the
load, the more kinetic and potential energy that gets stored and recovered
elastically, hence the cost of locomotion can be unchanged with speed or load
over a normal range of speeds.
The use of elastic
recoil of tendons is also found in many other large animals that run (such as horses
and turkeys) but to a much less dramatic extent in terms of energy savings as
that observed in kangaroos and wallabies with their huge hind limbs and hind
limb tendons. The general strategy
of elastic energy storage as a means of increasing locomotor energy efficiency
is also observed in a variety of swimming animals from squid to dolphins.
The use of elastic energy
storage could be considered in the human design of all sorts of moving
structures to increase energy efficiency.
“Spring loaded locomotion” has been used in the design of the pogo stick
and some prosthetic legs.
Excerpt
"Moderate to large macropodids can increase their speed while hopping with little or no increase in energy expenditure. This has been interpreted by some workers as resulting from elastic energy savings in their hindlimb tendons. For this to occur, the muscle fibers must transmit force to their tendons with little or no length change. To test whether this is the case, we made in vivo measurements of muscle fiber length change and tendon force in the lateral gastrocnemius (LG) and plantaris (PL) muscles of tammar wallabies Macropus eugenii as they hopped at different speeds on a treadmill. Muscle fiber length changes were less than +/-0.5 mm in the plantaris and +/-2.2 mm in the lateral gastrocnemius, representing less than 2 % of total fiber length in the plantaris and less than 6 % in the lateral gastrocnemius, with respect to resting length. The length changes of the plantaris fibers suggest that this occurred by means of elastic extension of attached cross-bridges. Much of the length change in the lateral gastrocnemius fibers occurred at low force early in the stance phase, with generally isometric behavior at higher forces. Fiber length changes did not vary significantly with increased hopping speed in either muscle (P>0.05), despite a 1. 6-fold increase in muscle-tendon force between speeds of 2.5 and 6.0 m s-1. Length changes of the PL fibers were only 7+/-4 % and of the LG fibers 34+/-12 % (mean +/- S.D., N=170) of the stretch calculated for their tendons, resulting in little net work by either muscle (plantaris 0.01+/-0.03 J; gastrocnemius -0.04+/-0.30 J; mean +/- s.d. ). In contrast, elastic strain energy stored in the tendons increased with increasing speed and averaged 20-fold greater than the shortening work performed by the two muscles. These results show that an increasing amount of strain energy stored within the hindlimb tendons is usefully recovered at faster steady hopping speeds, without being dissipated by increased stretch of the muscles' fibers. This finding supports the view that tendon elastic saving of energy is an important mechanism by which this species is able to hop at faster speeds with little or no increase in metabolic energy expenditure." (Biewener 1998:1681)
About the inspiring organism
Tammar Wallaby
Macropus eugenii (Desmarest, 1817)
[Tammar wallaby]
IUCN Red List Status: Least Concern
Habitat(s): Shrubland
Some organism data provided by: ITIS: The Integrated Taxonomic Information System
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist
Bioinspired products and application ideas
Application Ideas: Amplification strategy for kinetic energy. Kinetic energy storage product for cars. Prosthetics. Machines that capture energy to use in other applications, pumps that recapture input energy.
Industrial Sector(s) interested in this strategy: Manufacturing, Transportation
References
Alexander, RM. 1984. Elastic energy stores in running vertebrates. American Zoologist. 24(1): 85-94.
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Biewener, AA; Baudinette, RV. 1995. In vivo muscle energy storage during steady-speed hopping of tammar wallabies (Macropus eugenii). Journal of Experimental Biology. 198: 1829-1841.
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Biewener, AA; Konieczynski, DD; Baudinette, RV. 1998. In vivo muscle force-length behavior during steady speed hopping in tammar wallabies. Journal of Experimental Biology. 201: 1681-1694.
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Baudinette, RV; Biewener, AA. 1998. Young wallabies get a free ride. Nature. 395: 653-654.
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Dawson, TJ; Taylor, CR. 1973. Energetic cost of locomotion in kangaroos. Nature. 246: 313-314.
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Pabst, DA. 1996. Springs in swimming animals. American Zoologist. 36: 723-735.
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Lehmann JF; Price R; Boswell-Bessette S; Dralle A; Questad K; De Lateur BJ. 1993. Comprehensive analysis of energy storing prosthetic feet: Flex foot and Seattle foot versus standard SACH foot. 74: 1225-1231.
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