Passive bipedal running

McGeer, Tad

doi:10.1098/rspb.1990.0030

Cited by 141 publications

(70 citation statements)

References 8 publications

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“…Representations of the running leg as a simple spring have described the mechanics of a running leg remarkably well (2,11,12,15,16,18,19,(25)(26)(27). It has been shown that the physical musculoskeletal elastic components of the leg (tendons, ligaments, and muscles) are used to minimize metabolic cost while running (1,2,(8)(9)(10).…”

Section: In Their Groundbreaking Work Mcmahon and Greenementioning

confidence: 99%

Energetics and mechanics of human running on surfaces of different stiffnesses

Kerdok

Biewener

McMahon

et al. 2002

Journal of Applied Physiology

305

246

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. Energetics and mechanics of human running on surfaces of different stiffnesses. J Appl Physiol 92: 469-478, 2002; 10.1152/ japplphysiol.01164.2000.-Mammals use the elastic components in their legs (principally tendons, ligaments, and muscles) to run economically, while maintaining consistent support mechanics across various surfaces. To examine how leg stiffness and metabolic cost are affected by changes in substrate stiffness, we built experimental platforms with adjustable stiffness to fit on a force-plate-fitted treadmill. Eight male subjects [mean body mass: 74.4 Ϯ 7.1 (SD) kg; leg length: 0.96 Ϯ 0.05 m] ran at 3.7 m/s over five different surface stiffnesses (75.4, 97.5, 216.8, 454.2, and 945.7 kN/m). Metabolic, ground-reaction force, and kinematic data were collected. The 12.5-fold decrease in surface stiffness resulted in a 12% decrease in the runner's metabolic rate and a 29% increase in their leg stiffness. The runner's support mechanics remained essentially unchanged. These results indicate that surface stiffness affects running economy without affecting running support mechanics. We postulate that an increased energy rebound from the compliant surfaces studied contributes to the enhanced running economy. biomechanics; locomotion; leg stiffness; metabolic rate IN THEIR GROUNDBREAKING work, McMahon and Greene (29) investigated the effects of surface stiffness (k surf ) on running mechanics. Their study sought to determine whether it was possible to build a track surface that would enhance performance and decrease injury. Their work showed that a range of k surf values existed over which a runner's performance was enhanced by decreasing foot-ground contact time (t c ), decreasing the initial spike in peak vertical ground reaction force (f peak ), and increasing stride length. Tracks built within this enhanced performance range at Harvard University, Yale University, and Madison Square Garden have been shown to increase running speeds by 2-3% and to decrease running injuries by 50% (29). Despite the success of these "tuned tracks," the mechanisms underlying the performance enhancement are not clearly understood.A major assumption of McMahon and Greene's (29) was that the running leg and surface could be represented as a simple spring and mass (Fig.

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Section: In Their Groundbreaking Work Mcmahon and Greenementioning

confidence: 99%

Energetics and mechanics of human running on surfaces of different stiffnesses

Kerdok

Biewener

McMahon

et al. 2002

Journal of Applied Physiology

305

246

View full text Add to dashboard Cite

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“…In walking, the body behaves like an inverted pendulum (McGeer, 1990a;Mochon & McMahon, 1980), yielding highly conservative exchanges of kinetic and potential energy. In running, the body behaves like a bouncing ball, in which kinetic energy is converted to elastic energy stored in the tendons and muscles of the stance leg (Blickhan, 1989;McGeer, 1990b;McMahon & Cheng, 1990). A transition from the pendular walking mode to the elastic running mode could be brought about by an increase in propulsive force in the stance phase that propels the body into the air.…”

Section: Theories Of Gait Transitionsmentioning

confidence: 99%

Why change gaits? Dynamics of the walk-run transition.

Diedrich¹,

Warren²

1995

Journal of Experimental Psychology: Human Perception and Perfor

318

265

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Why do humans switch from walking to running at a particular speed? It is proposed that gait transitions behave like nonequilibrium phase transitions between attractors. Experiment 1 examined walking and running on a treadmill while speed was varied. The transition occurred at the equal-energy separatrix between gaits, with predicted shifts in stride length and frequency, a qualitative reorganization in the relative phasing of segments within a leg, a sudden jump in relative phase, enhanced fluctuations in relative phase, and hysteresis. Experiment 2 dissociated speed, frequency, and stride length to show that the transition occurred at a constant speed near the energy separatrix. Results are consistent with a dynamic theory of locomotion in which preferred gaits are characterized by stable phase relationships and minimum energy expenditure, and gait transitions by a loss of stability and the reduction of energetic costs.Motor behavior in humans and animals exhibits two notable features: the presence of stable patterns of coordination and the sudden reorganization that occurs when switching between them. Much research has been directed at describing individual motor patterns such as walking and reaching, but the study of behavioral transitions may reveal principles of the formation of coordinative patterns. Locomotion offers a model system for the study of both, for it is a fundamental, fluent, and complex behavior that is likely to share basic characteristics with other skilled actions. In this article, we examine the shift between walking and running in humans and offer a qualitative dynamic theory of gait transitions.As speed increases, humans and other animals shift from a walking gait to a running gait at a characteristic speed. Why does this occur? A common view is that each gait is orchestrated by a central motor plan, such as a motor program or spinal pattern generator, and that gait transitions simply involve switching between plans (e.g., Shapiro, Zernicke, Gregor, & Diestel, 1981). This view does not offer predictions about the details of behavior at gait transitions. By contrast, we propose that gait transitions are a consequence of the intrinsic dynamics of a complex system, with properties characteristic of bifurcations between attractors. We show that the walk-run (W-R) transition exhibits features of a nonequilibrium phase transition and that it occurs at a speed that tends to reduce energetic costs. This

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“…Elastic couplings acting as return springs have first been used solely in passive dynamic running [29,38]. Later an elastic coupling in the form of a hip spring was also used in spatial passive dynamic walking to adjust the step frequency to the frequency of the toddling motion for stabilization [26].…”

Section: Introductionmentioning

confidence: 99%

Optimization of energy efficiency of walking bipedal robots by use of elastic couplings in the form of mechanical springs

et al. 2015

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This paper presents a method to optimize the energy efficiency of walking bipedal robots by more than 50 % in a speed range from 0.3 to 2.3 m/s using elastic couplings -mechanical springs with movement speed independent parameters. The considered robot consists of a trunk, two stiff legs and two actuators in the hip joints. It is modeled as underactuated system to make use of its natural dynamics and feedback controlled with input-output linearization. A numerical optimization of the joint angle trajectories as well as the elastic couplings is performed to minimize the average energy expenditure over the whole speed range. The elastic couplings increase the swing leg motion's natural frequency thus making smaller steps more efficient which reduce the impact loss at the touchdown of the swing leg. The process of energy turnover is investigated for the robot with and without elastic couplings. Furthermore, the influence of the elastic couplings' topology, its degree of nonlinearity, the mass distribution, the joint friction, the coefficient of static friction and the selected actuator is analyzed. It is shown that the optimization of the robot's motion and elastic coupling towards energy efficiency leads to a slightly slower convergence rate of the controller, yet no loss of stability and a lower sensitivity with respect to disturbances. The optimal elastic coupling discovered by the numerical optimization is a linear torsion spring between the legs.

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Passive bipedal running

Cited by 141 publications

References 8 publications

Energetics and mechanics of human running on surfaces of different stiffnesses

Energetics and mechanics of human running on surfaces of different stiffnesses

Why change gaits? Dynamics of the walk-run transition.

Optimization of energy efficiency of walking bipedal robots by use of elastic couplings in the form of mechanical springs

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