The energetic cost of walking

A comparison of predictive methods

Patricia Ann Kramer, Adam Sylvester

Research output: Contribution to journalArticle

Abstract

Background: The energy that animals devote to locomotion has been of intense interest to biologists for decades and two basic methodologies have emerged to predict locomotor energy expenditure: those based on metabolic and those based on mechanical energy. Metabolic energy approaches share the perspective that prediction of locomotor energy expenditure should be based on statistically significant proxies of metabolic function, while mechanical energy approaches, which derive from many different perspectives, focus on quantifying the energy of movement. Some controversy exists as to which mechanical perspective is "best", but from first principles all mechanical methods should be equivalent if the inputs to the simulation are of similar quality. Our goals in this paper are 1) to establish the degree to which the various methods of calculating mechanical energy are correlated, and 2) to investigate to what degree the prediction methods explain the variation in energy expenditure. Methodology/Principal Findings: We use modern humans as the model organism in this experiment because their data are readily attainable, but the methodology is appropriate for use in other species. Volumetric oxygen consumption and kinematic and kinetic data were collected on 8 adults while walking at their self-selected slow, normal and fast velocities. Using hierarchical statistical modeling via ordinary least squares and maximum likelihood techniques, the predictive ability of several metabolic and mechanical approaches were assessed. We found that all approaches are correlated and that the mechanical approaches explain similar amounts of the variation in metabolic energy expenditure. Most methods predict the variation within an individual well, but are poor at accounting for variation between individuals. Conclusion: Our results indicate that the choice of predictive method is dependent on the question(s) of interest and the data available for use as inputs. Although we used modern humans as our model organism, these results can be extended to other species.

Original languageEnglish (US)
Article numbere21290
JournalPLoS One
Volume6
Issue number6
DOIs
StatePublished - 2011
Externally publishedYes

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walking
Walking
Energy Metabolism
Costs and Cost Analysis
Costs
energy expenditure
energy
methodology
Maximum likelihood
Proxy
Locomotion
Kinematics
Animals
Least-Squares Analysis
Biomechanical Phenomena
Oxygen Consumption
Oxygen
Kinetics
prediction
organisms

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

The energetic cost of walking : A comparison of predictive methods. / Kramer, Patricia Ann; Sylvester, Adam.

In: PLoS One, Vol. 6, No. 6, e21290, 2011.

Research output: Contribution to journalArticle

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