Simultaneous positive and negative external mechanical work in human walking

Donelan, J. Maxwell; Kram, Rodger; Kuo, Arthur D.

doi:10.1016/s0021-9290(01)00169-5

Cited by 454 publications

(558 citation statements)

References 16 publications

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“…This positive power continued until slightly before the next forelimb lift-off, raising the elephant's CM to its highest position presumably via the trailing forelimb's push-off. Thereafter, the mechanical power became slightly negative, probably due to the simultaneous positive and negative work of the ipsilateral forelimb and hindlimb (Donelan et al 2002). After the contralateral hindlimb landed on the ground, the animal passed into its next triple support phase.…”

Section: Resultsmentioning

confidence: 99%

The three-dimensional locomotor dynamics of African (Loxodonta africana) and Asian (Elephas maximus) elephants reveal a smooth gait transition at moderate speed

Ren

Hutchinson

2007

J. R. Soc. Interface.

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We examined whether elephants shift to using bouncing (i.e. running) mechanics at any speed. To do this, we measured the three-dimensional centre of mass (CM) motions and torso rotations of African and Asian elephants using a novel multisensor method. Hundreds of continuous stride cycles were recorded in the field. African and Asian elephants moved very similarly. Near the mechanically and metabolically optimal speed (a Froude number (Fr) of 0.09), an inverted pendulum mechanism predominated. With increasing speed, the locomotor dynamics quickly but continuously became less like vaulting and more like bouncing. Our mechanical energy analysis of the CM suggests that at a surprisingly slow speed (approx. 2.2 m s K1 , Fr 0.25), the hindlimbs exhibited bouncing, not vaulting, mechanics during weight support. We infer that a gait transition happens at this relatively slow speed: elephants begin using their compliant hindlimbs like pogo sticks to some extent to drive the body, bouncing over their relatively stiff, vaulting forelimbs. Hence, they are not as rigid limbed as typically characterized for graviportal animals, and use regular walking as well as at least one form of running gait.

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Section: Resultsmentioning

confidence: 99%

The three-dimensional locomotor dynamics of African (Loxodonta africana) and Asian (Elephas maximus) elephants reveal a smooth gait transition at moderate speed

Ren

Hutchinson

2007

J. R. Soc. Interface.

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“…The vertical component of CM velocity is upwards at the start of the step and downwards at the end. A number of studies have addressed the step-to-step transition issue [5,[9][10][11][27][28][29] assuming that it leads to a collision during which energy is lost. The empirical data, however, particularly for the vertical component of the CM velocity, show considerable departures from model predictions over the first and last quarters of the step resulting in minimal vertical velocity at the start and end of the step.…”

Section: Discussionmentioning

confidence: 99%

“…Recent work of this group has tended to focus on the transitions from one step to the next [9][10][11] . The group, as well as other researchers, have also presented many extended versions of IP models including springs, dampers, telescopic actuators, additional segments and joints.…”

Section: Introductionmentioning

confidence: 99%

The strengths and weaknesses of inverted pendulum models of human walking

2015

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-An investigation into the kinematic and kinetic predictions of two "inverted pendulum" (IP) models of gait was undertaken. The first model consisted of a single leg, with anthropometrically correct mass and moment of inertia, and a point mass at the hip representing the rest of the body. A second model incorporating the physiological extension of a head-arms-trunk (HAT) segment, held upright by an actuated hip moment, was developed for comparison. Simulations were performed, using both models, and quantitatively compared with empirical gait data. There was little difference between the two models' predictions of kinematics and ground reaction force (GRF). The models agreed well with empirical data through mid-stance (20-40% of the gait cycle) suggesting that IP models adequately simulate this phase (mean error less than one standard deviation). IP models are not cyclic, however, and cannot adequately simulate double support and stepto-step transition. This is because the forces under both legs augment each other during double support to increase the vertical GRF. The incorporation of an actuated hip joint was the most novel change and added a new dimension to the classic IP model. The hip moment curve produced was similar to those measured during experimental walking trials. As a result, it was interpreted that the primary role of the hip musculature in stance is to keep the HAT upright. Careful consideration of the differences between the models throws light on what the different terms within the GRF equation truly represent.

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“…In accordance with Donelan et al (2002a), the integration constant for the vertical direction (c z ) was obtained by assuming the average vertical CoM velocity over a step to be zero.…”

Section: Discussionmentioning

confidence: 99%

Metabolic cost and mechanical work for the step-to-step transition in walking after successful total ankle arthroplasty

Doets

Vergouw

Veeger

et al. 2009

Human Movement Science

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The aim of this study was to investigate whether impaired ankle function after total ankle arthroplasty (TAA) affects the mechanical work during step-to-step transition and the metabolic cost of walking. Respiratory and force plate data were recorded in 11 patients and 11 healthy controls while they walked barefoot at a fixed walking speed (FWS, 1.25 m/s) and at their self-selected speed (SWS). At FWS metabolic cost of transport was 28% higher for the TAA group, but at SWS there was no significant increase. During the stepto-step transition, positive mechanical work generated by the trailing TAA leg was lower and negative mechanical work in the leading intact leg was larger. Despite the increase in mechanical work dissipation during double support, no significant differences in total mechanical work were found over a complete stride. This might be a result of methodological limitations of calculating mechanical work. Nevertheless, mechanical work dissipated during the step-to-step transition at FWS correlated significantly with metabolic cost of transport: r = .540. It was concluded that patients after successful TAA still experienced an impaired lower leg function, which contributed to an increase in mechanical energy dissipation during the step-to-step transition, and to an increase in the metabolic demand of walking.

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Simultaneous positive and negative external mechanical work in human walking

Cited by 454 publications

References 16 publications

The three-dimensional locomotor dynamics of African (Loxodonta africana) and Asian (Elephas maximus) elephants reveal a smooth gait transition at moderate speed

The three-dimensional locomotor dynamics of African (Loxodonta africana) and Asian (Elephas maximus) elephants reveal a smooth gait transition at moderate speed

The strengths and weaknesses of inverted pendulum models of human walking

Metabolic cost and mechanical work for the step-to-step transition in walking after successful total ankle arthroplasty

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