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Proc Biol Sci. 2003 Aug 22;270(1525):1741-6.

Human hopping on damped surfaces: strategies for adjusting leg mechanics.

Author information

1
Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA. ctmoritz@socrates.berkeley.edu

Abstract

Fast-moving legged animals bounce along the ground with spring-like legs and agilely traverse variable terrain. Previous research has shown that hopping and running humans maintain the same bouncing movement of the body's centre of mass on a range of elastic surfaces by adjusting their spring-like legs to exactly offset changes in surface stiffness. This study investigated human hopping on damped surfaces that dissipated up to 72% of the hopper's mechanical energy. On these surfaces, the legs did not act like pure springs. Leg muscles performed up to 24-fold more net work to replace the energy lost by the damped surface. However, considering the leg and surface together, the combination appeared to behave like a constant stiffness spring on all damped surfaces. By conserving the mechanics of the leg-surface combination regardless of surface damping, hoppers also conserved centre-of-mass motions. Thus, the normal bouncing movements of the centre of mass in hopping are not always a direct result of spring-like leg behaviour. Conserving the trajectory of the centre of mass by maintaining spring-like mechanics of the leg-surface combination may be an important control strategy for fast-legged locomotion on variable terrain.

PMID:
12965003
PMCID:
PMC1691428
DOI:
10.1098/rspb.2003.2435
[Indexed for MEDLINE]
Free PMC Article

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