scholarly journals The converse effects of speed and gravity on the energetics of walking and running

2017 ◽  
Author(s):  
S.J. Hasaneini ◽  
R.T. Schroeder ◽  
J.E.A. Bertram ◽  
A. Ruina
Keyword(s):  
Optimization Model ◽  
Human Subjects ◽  
Metabolic Cost ◽  
Energetic Cost ◽  
Model Parameters ◽  
Gravity Level ◽  
Reduced Gravity ◽  
Cost Of Transport ◽  
Highly Sensitive ◽  
Length Changes

AbstractThe energetic cost of transport for walking is highly sensitive to speed but relatively insensitive to changes in gravity level. Conversely, the cost of transport for running is highly sensitive to gravity level but not much to speed. Gait optimization with a minimally constrained bipedal model predicts a similar differential energetic response for walking and running even though the same model parameters and cost function are used for both gaits. This challenges previous assertions that the converse energetic responses are due to fundamentally different energy saving mechanisms in each gait. Our results suggest that energetics of both gaits are highly influenced by dissipative losses occurring as leg forces abruptly alter the center of mass path. The observed difference in energetic consequence of the performance condition in each gait is due to the effect the movement strategy of each gait has on the dissipative loss. The optimization model predictions are tested directly by measuring metabolic cost of human subjects walking and running at different speeds in normal and reduced gravity using a novel reduced gravity simulation apparatus. The optimization model also predicts other, sometimes subtle, aspects of gait such as step length changes. This is also directly tested in order to assess the fidelity of the model’s more nuanced predictions.

scholarly journals The rising cost of warming waters: effects of temperature on the cost of swimming in fishes

2011 ◽  
Vol 8 (2) ◽  
pp. 266-269 ◽  
Author(s):  
Andrew M. Hein ◽  
Katrina J. Keirsted
Keyword(s):  
Water Temperature ◽  
Fish Species ◽  
Global Climate ◽  
Swimming Performance ◽  
Metabolic Cost ◽  
Quantitative Model ◽  
The Body ◽  
Energetic Cost ◽  
Cost Of Transport ◽  
The Cost

Understanding the effects of water temperature on the swimming performance of fishes is central in understanding how fish species will respond to global climate change. Metabolic cost of transport (COT)—a measure of the energy required to swim a given distance—is a key performance parameter linked to many aspects of fish life history. We develop a quantitative model to predict the effect of water temperature on COT. The model facilitates comparisons among species that differ in body size by incorporating the body mass-dependence of COT. Data from 22 fish species support the temperature and mass dependencies of COT predicted by our model, and demonstrate that modest differences in water temperature can result in substantial differences in the energetic cost of swimming.

scholarly journals Individual Differences in Locomotor Function Predict the Capacity to Reduce Asymmetry and Modify the Energetic Cost of Walking Poststroke

2018 ◽  
Vol 32 (8) ◽  
pp. 701-713 ◽  
Author(s):  
Natalia Sánchez ◽  
James M. Finley
Keyword(s):  
Individual Differences ◽  
Metabolic Cost ◽  
Step Length ◽  
Energetic Cost ◽  
Cost Of Transport ◽  
Locomotor Function ◽  
Paretic Limb ◽  
Residual Capacity ◽  
Walking Economy ◽  
Baseline Cost

Changes in the control of the lower extremities poststroke lead to persistent biomechanical asymmetries during walking. These asymmetries are associated with an increase in energetic cost, leading to the possibility that reducing asymmetry can improve walking economy. However, the influence of asymmetry on economy may depend on the direction and cause of asymmetry. For example, impairments with paretic limb advancement may result in shorter paretic steps, whereas deficits in paretic support or propulsion result in shorter nonparetic steps. Given differences in the underlying impairments responsible for step length asymmetry, the capacity to reduce asymmetry and the associated changes in energetic cost may not be consistent across this population. Here, we identified factors explaining individual differences in the capacity to voluntarily reduce step length asymmetry and modify energetic cost during walking. A total of 24 individuals poststroke walked on a treadmill, with visual feedback of their step lengths to aid explicit modification of asymmetry. We found that individuals who took longer paretic steps had a greater capacity to reduce asymmetry and were better able to transfer the effects of practice to overground walking than individuals who took shorter paretic steps. In addition, changes in metabolic cost depended on the direction of asymmetry, baseline cost of transport, and reductions in specific features of spatiotemporal asymmetry. These results demonstrate that many stroke survivors retain the residual capacity to voluntarily walk more symmetrically on a treadmill and overground. However, whether reductions in asymmetry reduce metabolic cost depends on individual differences in impairments affecting locomotor function.

Joint-Space Dynamic Model of Metabolic Cost With Subject-Specific Energetic Parameters

2014 ◽  
Author(s):  
Dustyn Roberts ◽  
Howard Hillstrom ◽  
Joo H. Kim
Keyword(s):  
Dynamic Model ◽  
Metabolic Cost ◽  
Joint Space ◽  
Human Motion ◽  
Metabolic Energy ◽  
Model Parameters ◽  
Cost Of Transport ◽  
Walking Speeds ◽  
The Cost ◽  
Metabolic Energy Expenditure

Metabolic energy expenditure (MEE) is commonly used to characterize human motion. In this study, a general joint-space dynamic model of MEE is developed by integrating the principles of thermodynamics and multibody system dynamics in a joint-space model that enables the evaluation of MEE without the limitations inherent in experimental measurements or muscle-space models. Muscle-space energetic components are mapped to the joint space, in which the MEE model is formulated. A constrained optimization algorithm is used to estimate the model parameters from experimental walking data. The joint-space parameters estimated directly from active subjects provide reliable estimates of the trend of the cost of transport at different walking speeds. The quantities predicted by this model, such as cost of transport, can be used as strong complements to experimental methods to increase the reliability of results and yield unique insights for various applications.

A model of scale effects in mammalian quadrupedal running

2002 ◽  
Vol 205 (7) ◽  
pp. 959-967 ◽  
Author(s):  
Hugh M. Herr ◽  
Gregory T. Huang ◽  
Thomas A. McMahon
Keyword(s):  
Time Course ◽  
Scale Effects ◽  
Metabolic Cost ◽  
Integrative Model ◽  
Stride Frequency ◽  
Published Data ◽  
Model Parameters ◽  
Cost Of Transport ◽  
Vertical Stiffness ◽  
Leg Stiffness

SUMMARYAlthough the effects of body size on mammalian locomotion are well documented, the underlying mechanisms are not fully understood. Here, we present a computational model of the mechanics, control and energetics that unifies some well-known scale effects in running quadrupeds. The model consists of dynamic, physics-based simulations of six running mammals ranging in size from a chipmunk to a horse (0.115-676 kg). The `virtual animals' are made up of rigid segments (head, trunk and four legs) linked by joints and are similar in morphology to particular species. In the model, each stance limb acts as a spring operating within a narrow range of stiffness, forward motion is powered and controlled by active hip and shoulder torques, and metabolic cost is predicted from the time course of supporting body weight. Model parameters that are important for stability (joint stiffnesses,limb-retraction times and target positions and velocities of the limbs) are selected such that (i) running kinematics (aerial height, forward speed and body pitch) is smooth and periodic and (ii) overall leg stiffness is in agreement with published data. Both trotting and galloping gaits are modeled,and comparisons across size are made at speeds that are physiologically similar among species. Model predictions are in agreement with data on vertical stiffness, limb angles, metabolic cost of transport, stride frequency, peak force and duty factor. This work supports the idea that a single, integrative model can predict important features of running across size by employing simple strategies to control overall leg stiffness. More broadly, the model provides a quantitative framework for testing hypotheses that relate limb control, stability and metabolic cost.

scholarly journals Associations Between Foot Placement Asymmetries and Metabolic Cost of Transport in Hemiparetic Gait

2016 ◽  
Vol 31 (2) ◽  
pp. 168-177 ◽  
Author(s):  
James M. Finley ◽  
Amy J. Bastian
Keyword(s):  
Walking Speed ◽  
Metabolic Cost ◽  
Positive Association ◽  
Stroke Survivor ◽  
Gas Analysis ◽  
Stroke Survivors ◽  
Cost Of Transport ◽  
Foot Placement ◽  
Hemiparetic Gait ◽  
All Speeds

Stroke survivors often have a slow, asymmetric walking pattern. They also walk with a higher metabolic cost than healthy, age-matched controls. It is often assumed that spatial-temporal asymmetries contribute to the increased metabolic cost of walking poststroke. However, elucidating this relationship is made challenging because of the interdependence between spatial-temporal asymmetries, walking speed, and metabolic cost. Here, we address these potential confounds by measuring speed-dependent changes in metabolic cost and implementing a recently developed approach to dissociate spatial versus temporal contributions to asymmetry in a sample of stroke survivors. We used expired gas analysis to compute the metabolic cost of transport (CoT) for each participant at 4 different walking speeds: self-selected speed, 80% and 120% of their self-selected speed, and their fastest comfortable speed. We also computed CoT for a sample of age- and gender-matched control participants who walked at the same speeds as their matched stroke survivor. Kinematic data were used to compute the magnitude of a number of variables characterizing spatial-temporal asymmetries. Across all speeds, stroke survivors had a higher CoT than controls. We also found that our sample of stroke survivors did not choose a self-selected speed that minimized CoT, contrary to typical observations in healthy controls. Multiple regression analyses revealed negative associations between speed and CoT and a positive association between asymmetries in foot placement relative to the trunk and CoT. These findings suggest that interventions designed to increase self-selected walking speed and reduce foot-placement asymmetries may be ideal for improving walking economy poststroke.

scholarly journals Walking in simulated reduced gravity: mechanical energy fluctuations and exchange

1999 ◽  
Vol 86 (1) ◽  
pp. 383-390 ◽  
Author(s):  
Timothy M. Griffin ◽  
Neil A. Tolani ◽  
Rodger Kram
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Inverted Pendulum ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Gravitational Potential Energy ◽  
Reduced Gravity

Walking humans conserve mechanical and, presumably, metabolic energy with an inverted pendulum-like exchange of gravitational potential energy and horizontal kinetic energy. Walking in simulated reduced gravity involves a relatively high metabolic cost, suggesting that the inverted-pendulum mechanism is disrupted because of a mismatch of potential and kinetic energy. We tested this hypothesis by measuring the fluctuations and exchange of mechanical energy of the center of mass at different combinations of velocity and simulated reduced gravity. Subjects walked with smaller fluctuations in horizontal velocity in lower gravity, such that the ratio of horizontal kinetic to gravitational potential energy fluctuations remained constant over a fourfold change in gravity. The amount of exchange, or percent recovery, at 1.00 m/s was not significantly different at 1.00, 0.75, and 0.50 G (average 64.4%), although it decreased to 48% at 0.25 G. As a result, the amount of work performed on the center of mass does not explain the relatively high metabolic cost of walking in simulated reduced gravity.

Energetics of walking and running: insights from simulated reduced-gravity experiments

1992 ◽  
Vol 73 (6) ◽  
pp. 2709-2712 ◽  
Author(s):  
C. T. Farley ◽  
T. A. McMahon
Keyword(s):  
Body Weight ◽  
Energy Consumption ◽  
Energetic Cost ◽  
Reduced Gravity ◽  
Low Levels

On Earth, a person uses about one-half as much energy to walk a mile as to run a mile. On another planet with lower gravity, would walking still be more economical than running? When people carry weights while they walk or run, energetic cost increases in proportion to the added load. It would seem to follow that if gravity were reduced, energetic cost would decrease in proportion to body weight in both gaits. However, we find that under simulated reduced gravity, the rate of energy consumption decreases in proportion to body weight during running but not during walking. When gravity is reduced by 75%, the rate of energy consumption is reduced by 72% during running but only by 33% during walking. Because reducing gravity decreases the energetic cost much more for running than for walking, walking is not the cheapest way to travel a mile at low levels of gravity. These results suggest that the link between the mechanics of locomotion and energetic cost is fundamentally different for walking and for running.

scholarly journals Elastic energy savings and active energy cost in a simple model of running

2021 ◽  
Vol 17 (11) ◽  
pp. e1009608
Author(s):  
Ryan T. Schroeder ◽  
Arthur D. Kuo
Keyword(s):  
Elastic Energy ◽  
Energy Cost ◽  
Energy Savings ◽  
Mechanical Energy ◽  
Metabolic Cost ◽  
The Body ◽  
Metabolic Energy ◽  
Energetic Cost ◽  
Mass Model ◽  
Human Running

The energetic economy of running benefits from tendon and other tissues that store and return elastic energy, thus saving muscles from costly mechanical work. The classic “Spring-mass” computational model successfully explains the forces, displacements and mechanical power of running, as the outcome of dynamical interactions between the body center of mass and a purely elastic spring for the leg. However, the Spring-mass model does not include active muscles and cannot explain the metabolic energy cost of running, whether on level ground or on a slope. Here we add explicit actuation and dissipation to the Spring-mass model, and show how they explain substantial active (and thus costly) work during human running, and much of the associated energetic cost. Dissipation is modeled as modest energy losses (5% of total mechanical energy for running at 3 m s-1) from hysteresis and foot-ground collisions, that must be restored by active work each step. Even with substantial elastic energy return (59% of positive work, comparable to empirical observations), the active work could account for most of the metabolic cost of human running (about 68%, assuming human-like muscle efficiency). We also introduce a previously unappreciated energetic cost for rapid production of force, that helps explain the relatively smooth ground reaction forces of running, and why muscles might also actively perform negative work. With both work and rapid force costs, the model reproduces the energetics of human running at a range of speeds on level ground and on slopes. Although elastic return is key to energy savings, there are still losses that require restorative muscle work, which can cost substantial energy during running.

scholarly journals Factors affecting metabolic cost of transport during a multi-stage running race

2013 ◽  
Vol 217 (5) ◽  
pp. 787-795 ◽  
Author(s):  
S. Lazzer ◽  
P. Taboga ◽  
D. Salvadego ◽  
E. Rejc ◽  
B. Simunic ◽  
...  
Keyword(s):  
Metabolic Cost ◽  
Cost Of Transport ◽  
Factors Affecting ◽  
Multi Stage

Reduced prosthetic stiffness lowers the metabolic cost of running for athletes with bilateral transtibial amputations

2017 ◽  
Vol 122 (4) ◽  
pp. 976-984 ◽  
Author(s):  
Owen N. Beck ◽  
Paolo Taboga ◽  
Alena M. Grabowski
Keyword(s):  
Lower Limb ◽  
Metabolic Cost ◽  
Ground Reaction Forces ◽  
Metabolic Rates ◽  
Distance Running ◽  
Cost Of Transport ◽  
Leg Stiffness ◽  
Metabolic Costs ◽  
In Series ◽  
Reaction Forces

Inspired by the springlike action of biological legs, running-specific prostheses are designed to enable athletes with lower-limb amputations to run. However, manufacturer’s recommendations for prosthetic stiffness and height may not optimize running performance. Therefore, we investigated the effects of using different prosthetic configurations on the metabolic cost and biomechanics of running. Five athletes with bilateral transtibial amputations each performed 15 trials on a force-measuring treadmill at 2.5 or 3.0 m/s. Athletes ran using each of 3 different prosthetic models (Freedom Innovations Catapult FX6, Össur Flex-Run, and Ottobock 1E90 Sprinter) with 5 combinations of stiffness categories (manufacturer’s recommended and ± 1) and heights (International Paralympic Committee’s maximum competition height and ± 2 cm) while we measured metabolic rates and ground reaction forces. Overall, prosthetic stiffness [fixed effect (β) = 0.036; P = 0.008] but not height ( P ≥ 0.089) affected the net metabolic cost of transport; less stiff prostheses reduced metabolic cost. While controlling for prosthetic stiffness (in kilonewtons per meter), using the Flex-Run (β = −0.139; P = 0.044) and 1E90 Sprinter prostheses (β = −0.176; P = 0.009) reduced net metabolic costs by 4.3–4.9% compared with using the Catapult prostheses. The metabolic cost of running improved when athletes used prosthetic configurations that decreased peak horizontal braking ground reaction forces (β = 2.786; P = 0.001), stride frequencies (β = 0.911; P < 0.001), and leg stiffness values (β = 0.053; P = 0.009). Remarkably, athletes did not maintain overall leg stiffness across prosthetic stiffness conditions. Rather, the in-series prosthetic stiffness governed overall leg stiffness. The metabolic cost of running in athletes with bilateral transtibial amputations is influenced by prosthetic model and stiffness but not height. NEW & NOTEWORTHY We measured the metabolic rates and biomechanics of five athletes with bilateral transtibial amputations while running with different prosthetic configurations. The metabolic cost of running for these athletes is minimized by using an optimal prosthetic model and reducing prosthetic stiffness. The metabolic cost of running was independent of prosthetic height, suggesting that longer legs are not advantageous for distance running. Moreover, the in-series prosthetic stiffness governs the leg stiffness of athletes with bilateral leg amputations.

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