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      A Terradynamics of Legged Locomotion on Granular Media

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      Science
      American Association for the Advancement of Science (AAAS)

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          The spring-mass model for running and hopping

          R Blickhan (1989)
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            How Animals Move: An Integrative View

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              The sources of external work in level walking and running.

              The work done at each step during level walking and running to lift the centre of mass of the body, Wv, and to increase its forward speed, Wf, and the total mechanical energy involved (potential + kinetic) Wext, have been measured at various 'constant' speeds (2-32 km/hr) with the technique described by Cavagna (1975). 2. At intermediate speeds of walking (about 4 km/hr) Wv = Wf and Wext/km is at a minimum, as is the energy cost. At lower speeds Wv greater than Wf whereas at higher speeds Wf greather than Wv: in both cases Wext/km increases. 3. The recovery of mechanical energy, through the pendular motion characteristic of walking, was measured as (/Wv/ + /Wf/ - Wext)/(/Wv/ + /Wf/): it attains a maximum (about 65%) at intermediate speeds. 4. A simple model, assuming that in walking the body rotates as an inverted pendulum over the foot in contact with the ground, fits the experimental data better at intermediate speeds but is no longer tenable above 7 km/hr. 5. In running the recovery defined above is minimal (0-4% independent of speed), i.e. Wext congruent to /Wv/ + /Wf/: potential and kinetic energy of the body do not interchange but are simultaneously taken up and released by the muscles with a rate increasing markedly with the speed (from about 1 to 4 h.p.). 6. Wext increases linearly with the running speed Vf from a positive y intercept owing to the fact that Wv is practically constant independent of Vf. On the contrary, Wf = aVf2/(1 + bVf), where b is the ratio between the time spent in the air and the forward distance covered while on the ground during each step.
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                Author and article information

                Journal
                Science
                Science
                American Association for the Advancement of Science (AAAS)
                0036-8075
                1095-9203
                March 21 2013
                March 22 2013
                March 21 2013
                March 22 2013
                : 339
                : 6126
                : 1408-1412
                Article
                10.1126/science.1229163
                23520106
                87a6bf70-b05e-4836-8c46-030faf37494c
                © 2013
                History

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