Citation

Kim J, Bertram JEA. Gait Posture 2018; 64: 84-89.

Affiliation

Department of Cell Biology and Anatomy, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada. Electronic address: jbertram@ucalgary.ca.

Copyright

(Copyright © 2018, Elsevier Publishing)

DOI

10.1016/j.gaitpost.2018.05.020

PMID

29883939

Abstract

BACKGROUND: Humans alter gait in response to unusual gait circumstances to accomplish the task of walking. For instance, subjects spontaneously increase leg compliance at a step length threshold as step length increases. Here we test the hypothesis that this transition occurs based on the level of energy expenditure, where compliant walking becomes less energetically demanding at long step lengths. RESEARCH QUESTION: To map and compare the metabolic cost of normal and compliant walking as step length increases.

METHODS: 10 healthy individuals walked on a treadmill using progressively increasing step lengths (100%, 120%, 140% and 160% of preferred step length), in both normal and compliant leg walking as energy expenditure was recorded via indirect calorimetry. Leg compliance was controlled by lowering the center-of-mass trajectory during stance, forcing the leg to flex and extend as the body moved over the foot contact.

RESULTS: For normal step lengths, compliant leg walking was more costly than normal walking gait, but compliant leg walking energetic cost did not increase as rapidly for longer step lengths. This led to an intersection between normal and compliant walking cost curves at 114% relative step length (regression analysis; r² = 0.92 for normal walking; r² = 0.65 for compliant walking). SIGNIFICANCE: Compliant leg walking is less energetically demanding at longer step lengths where a spontaneous shift to compliant walking has been observed, suggesting the human motor control system is sensitive to energetic requirements and will employ alternate movement patterns if advantageous strategies are available. The transition could be attributed to the interplay between (i) leg work controlling body travel during single stance and (ii) leg work to control energy loss in the step-to-step transition. Compliant leg walking requires more stance leg work at normal step lengths, but involves less energy loss at the step-to-step transition for very long steps.

Copyright © 2018 Elsevier B.V. All rights reserved.

Language: en

Keywords

Cost surface; Human locomotion; Leg compliance; Metabolic cost; Optimization; Walking