Abstract
Metabolic energy expenditure during human gait is poorly understood. Mechanical energy loss during heel strike contributes to this energy expenditure. Previous work has estimated the energy absorption during heel strike as 0.8 J using an effective foot mass model. The aim of our study is to investigate the possibility of determining the energy absorption by more directly estimating the work done by the ground reaction force, the force-integral method. Concurrently another aim is to compare this method of direct determination of work to the method of an effective foot mass model. Participants of our experimental study were asked to walk barefoot at preferred speed. Ground reaction force and lower leg kinematics were collected at high sampling frequency (3000 Hz; 1295 Hz), with tight synchronization. The work done by the ground reaction force is 3.8 J, estimated by integrating this force over the foot-ankle deformation. The effective mass model is improved by dropping the assumption that foot-ankle deformation is maximal at the instant of the impact force peak. On theoretical grounds it is clear that in the presence of substantial damping that peak force and peak deformation do not occur simultaneously. The energy absorption results, due the vertical force only, corresponding to the force-integral method is similar to the results of the improved application of the effective mass model (2.7 J; 2.5 J). However the total work done by the ground reaction force calculated by the force-integral method is significantly higher than that of the vertical component alone. We conclude that direct estimation of the work done by the ground reaction force is possible and preferable over the use of the effective foot mass model. Assuming that energy absorbed is lost, the mechanical energy loss of heel strike is around 3.8 J for preferred walking speeds (≈ 1.3 m/s), which contributes to about 15–20% of the overall metabolic cost of transport.
Highlights
The metabolic cost of human walking is substantial
Experimental estimation of energy absorption during heel strike evaluation and treatment of gait disorders to have a thorough understanding of the processes underlying the metabolic energy expenditure during human locomotion, and to be able to measure the energy associated with these processes [5]
While it is debated in which phase positive muscle fiber mechanical work is primarily done [6,7,8,9,10,11,12], it is accepted that, during steady-motion level walking, the positive muscle fiber mechanical work serves to compensate for negative muscle fiber mechanical work, for negative work associated with air friction, and for mechanical energy lost in the foot-ground contact
Summary
Has it been reported to account for about 25% of the daytime energy expenditure of an office clerk [1], it is well established that walking distance of many people with a locomotor impairment, for instance following a stroke, is limited due to the associated metabolic cost [2,3,4]. We want to build on these findings and further investigate a major contributor to this unaccounted energy loss during the collision phase of walking
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