scholarly journals A low-cost method for carrying loads during human walking

2020 ◽  
Vol 223 (23) ◽  
pp. jeb216119
Author(s):  
Christopher J. Arellano ◽  
Obioma B. McReynolds ◽  
Shernice A. Thomas
Keyword(s):  
Low Cost ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
The Body ◽  
Human Walking ◽  
Metabolic Power ◽  
Arm Swing ◽  
Leg Motion ◽  
The Cost ◽  
Pendulum Dynamics

ABSTRACTHumans often perform tasks that require them to carry loads, but the metabolic cost of carrying loads depends on where the loads are positioned on the body. We reasoned that carrying loads at the arms’ center of mass (COM) during walking might be cheap because arm swing is thought to be dominated by passive pendulum dynamics. In contrast, we expected that carrying loads at the leg COM would be relatively expensive because muscular actuation is necessary to initiate and propagate leg swing. Therefore, we hypothesized that carrying loads at the arm COM while swinging would be cheaper than carrying loads at the leg COM. We further hypothesized that carrying loads at the arm COM while swinging would be more expensive than carrying loads at the waist, where the mass does not swing relative to the body. We measured net metabolic power, arm and leg motion, and the free vertical moment while subjects (n=12) walked on a treadmill (1.25 m s−1) without a load, and with 8 kg added to the arms (swinging versus not swinging), legs or waist. We found that carrying loads on the arms or legs altered arm swinging amplitude; however, the free vertical moment remained similar across conditions. Most notably, the cost of carrying loads on the swinging arms was 9% less than carrying at the leg COM (P<0.001), but similar to that at the waist (P=0.529). Overall, we found that carrying loads at the arm COM is just as cheap as carrying loads at the waist.

scholarly journals Disentangling the energetic costs of step time asymmetry and step length asymmetry in human walking

2021 ◽  
Author(s):  
Jan Stenum ◽  
Julia T. Choi
Keyword(s):  
Energy Cost ◽  
Metabolic Cost ◽  
Step Length ◽  
Human Walking ◽  
Metabolic Power ◽  
Healthy Human ◽  
Time Asymmetry ◽  
Double Support ◽  
Post Stroke ◽  
The Cost

The metabolic cost of walking in healthy individuals increases with spatiotemporal gait asymmetries. Pathological gait, such as post-stroke, often has asymmetry in step lengths and step times which may contribute to an increased energy cost. But paradoxically, enforcing step length symmetry does not reduce metabolic cost of post-stroke walking. The isolated and interacting costs of asymmetry in step times and step lengths remain unclear, because previous studies did not simultaneously enforce spatial and temporal gait asymmetries. Here, we delineate isolated costs of asymmetry in step times and step lengths in healthy human walking. We first show that the cost of step length asymmetry is predicted by the cost of taking two non-preferred step lengths (one short and one long), but that step time asymmetry adds an extra cost beyond the cost of non-preferred step times. The metabolic power of step time asymmetry is about 2.5 times greater than the cost of step length asymmetry. Furthermore, the costs are not additive when walking with asymmetric step times and step lengths: metabolic power of concurrent asymmetry in step lengths and step times is driven by the cost of step time asymmetry alone. The metabolic power of asymmetry is explained by positive mechanical power produced during single support phases to compensate for a net loss of center of mass power incurred during double support phases. These data may explain why metabolic cost remains invariant to step length asymmetry in post-stroke walking and suggests how effects of asymmetry on energy cost can be attenuated.

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 Effects of aging and arm swing on the metabolic cost of stability in human walking

2008 ◽  
Vol 41 (16) ◽  
pp. 3303-3308 ◽  
Author(s):  
Justus D. Ortega ◽  
Leslie A. Fehlman ◽  
Claire T. Farley
Keyword(s):  
Metabolic Cost ◽  
Human Walking ◽  
Arm Swing ◽  
Effects Of Aging

scholarly journals Simulated hemiparesis increases optimal spatiotemporal gait asymmetry but not metabolic cost

2021 ◽  
Author(s):  
Russell T Johnson ◽  
Nicholas August Bianco ◽  
James Finley
Keyword(s):  
Gait Speed ◽  
Metabolic Cost ◽  
The Body ◽  
Musculoskeletal Modeling ◽  
Cost Of Transport ◽  
Gait Patterns ◽  
Post Stroke ◽  
The Cost ◽  
Future Work ◽  
Isometric Muscle

Several neuromuscular impairments, such as weakness (hemiparesis), occur after an individual has a stroke, and these impairments primarily affect one side of the body more than the other. Predictive musculoskeletal modeling presents an opportunity to investigate how a specific impairment affects gait performance post-stroke. Therefore, our aim was to use to predictive simulation to quantify the spatiotemporal asymmetries and changes to metabolic cost that emerge when muscle strength is unilaterally reduced. We also determined how forced spatiotemporal symmetry affects metabolic cost. We modified a 2-D musculoskeletal model by uniformly reducing the peak isometric muscle force in all muscles unilaterally. We then solved optimal control simulations of walking across a range of speeds by minimizing the sum of the cubed muscle excitations across all muscles. Lastly, we ran additional optimizations to test if reducing spatiotemporal asymmetry would result in an increase in metabolic cost. Our results showed that the magnitude and direction of effort-optimal spatiotemporal asymmetries depends on both the gait speed and level of weakness. Also, the optimal metabolic cost of transport was 1.25 m/s for the symmetrical and 20% weakness models but slower (1.00 m/s) for the 40% and 60% weakness models, suggesting that hemiparesis can account for a portion of the slower gait speed seen in people post-stroke. Adding spatiotemporal asymmetry to the cost function resulted in small increases (~4%) in metabolic cost. Overall, our results indicate that spatiotemporal asymmetry may be optimal for people post-stroke, who have asymmetrical neuromuscular impairments. Additionally, the effect of speed and level of weakness on spatiotemporal asymmetry may explain the well-known heterogenous distribution of spatiotemporal asymmetries observed in the clinic. Future work could extend our results by testing the effects of other impairments on optimal gait strategies, and therefore build a more comprehensive understanding of the gait patterns in people post-stroke.

Metabolic cost of head-stand posture

1962 ◽  
Vol 17 (1) ◽  
pp. 117-118 ◽  
Author(s):  
Shanker Rao
Keyword(s):  
Medical Students ◽  
Energy Expenditure ◽  
Human Body ◽  
Metabolic Cost ◽  
The Body ◽  
Erect Posture ◽  
The Mean ◽  
The Cost ◽  
Mean Cost

Metabolic cost to the human body of various postures has been assessed by many workers. The cost with the body in the topsy-turvy posture, or while “standing on the head,” has not been reported so far. Energy expenditure was calculated indirectly by estimating the amount of oxygen consumed while in a particular posture. A Benedict-type recording spirometer was used for this purpose. The subjects were six healthy medical students. The mean cost of standing on the head was determined to be 336 ml, or 1.62 kcal/min, and that of “suspension by the feet” to be 300 ml, or 1.44 kcal/min. The possible causes of increased consumption in relation to the “standing erect” posture are discussed. Submitted on May 26, 1961

Optimization-based subject-specific planar human vertical jumping prediction: Effect of elbow flexion and weighted vest

2021 ◽  
pp. 095441192110440
Author(s):  
Juan Baus ◽  
John R Harry ◽  
James Yang
Keyword(s):  
Center Of Mass ◽  
Elbow Flexion ◽  
The Body ◽  
Loading Conditions ◽  
Arm Swing ◽  
Design Variables ◽  
Vertical Jumping ◽  
Reaction Forces ◽  
Body Center ◽  
Mass Position

Jumping strategies differ considerably depending on athletes’ physical activity demands. In general, the jumping motion is desired to have excellent performance and low injury risk. Both of these outcomes can be achieved by modifying athletes’ jumping and landing mechanics. This paper presents a consecutive study on the optimization-based subject-specific planar human vertical jumping to test different loading conditions (weighted vest) during jumping with or without elbow flexion during the arm-swing based on the validated prediction model in the first part of this study. The sagittal plane skeletal model simulates the weighting, unweighting, breaking, propulsion phases and considers four loading conditions: 0%, 5%, 10%, and 15% body weight. Results show that the maximum ground reaction forces, the body center of mass position, and velocities at the take-off instant are different for different loading conditions and with/without elbow flexion. The optimization formulation is solved using MATLAB® with 35 design variables with 197 nonlinear constraints for a five-segment body model and 42 design variables with 227 nonlinear constraints for a six-segment body model. Both models are computationally efficient, and they can predict ground reaction forces, the body center of mass position, and velocity. This work is novel in the sense that presents a simulation model capable of considering different external loading conditions and the effect of elbow flexion during arm swing.

scholarly journals STUDY OF THE INFLUENCE OF GEOTEXTILE MATERIALS DURING CONSTRUCTION OF DAMS

2021 ◽  
pp. 112-121
Author(s):  
H.V. Slobodianyk ◽  
◽  
K.Z. Shokot ◽  
Keyword(s):  
Bearing Capacity ◽  
Building Materials ◽  
Computational Models ◽  
Low Cost ◽  
Resistance Coefficient ◽  
The Body ◽  
Soil Reinforcement ◽  
Vertical Movements ◽  
The Road ◽  
The Cost

One of the real and promising ways to expand the range and types of structures for strengthening the slopes of embankments and dams is the use of geotextile materials. In the structures under consideration, they can perform protective, filtering, separating, reinforcing functions and moreover they improve the working conditions of the soil and layers of road pavements on the sides of the road and in the slope parts, increasing their stability. The use of geotextiles makes it possible to develop technically and economically effective design solutions. As the analysis of literature data has shown, soil reinforcement is an effective method for increasing the bearing capacity of foundations at a relatively low cost. Therefore, research, both theoretical and experimental, the development and creation of computational models taking into account the influence of reinforcing elements is an urgent problem. The paper considers the stress-strain state of a bulk dam without and with two options for the location of geotextiles. On the basis of the carried out numerical modeling, it is shown how when using geotextiles, the bearing capacity of a structure increases, while the volume of materials decreases. At the second stage, on the basis of the calculations, the optimal variant of the location of the geotextile material in the body of the structure was selected with the best technical and economic indicators. The research results show that when reinforcing the embankment with open clips in two rows – in the upper and lower parts-the smallest horizontal and vertical movements are obtained at almost the same total stresses. At the same time, the required value of the resistance coefficient is achieved, and the volume of soil is reduced. Thus, it can be concluded that the use of geotextile materials can reduce the cost of basic building materials while increasing operational characteristics and extending the service life of the structure.

Upper Extremity Function in Running. I: Center of Mass and Propulsion Considerations

1987 ◽  
Vol 3 (3) ◽  
pp. 222-241 ◽  
Author(s):  
Richard N. Hinrichs ◽  
Peter R. Cavanagh ◽  
Keith R. Williams
Keyword(s):  
Center Of Mass ◽  
Three Dimensional ◽  
The Body ◽  
Horizontal Velocity ◽  
Distance Runners ◽  
Contact Phase ◽  
Arm Swing ◽  
Vertical Range ◽  
Body Center ◽  
Recreational Runners

Ten male recreational runners were filmed using three-dimensional cinematography while running on a treadmill at 3.8 m/s, 4.5 m/s, and 5.4 m/s. A 14-segment mathematical model was used to examine the influence of the arm swing on the three-dimensional motion of the body center of mass (CM), and on the vertical and horizontal propulsive impulses (“lift” and “drive”) on the body over the contact phase of the running cycle. The arms were found to reduce the horizontal excursions of the body CM both front to back and side to side, thus tending to make a runner's horizontal velocity more constant. The vertical range of motion of the body CM was increased by the action of the arms. The arms were found to make a small but important contribution to lift, roughly 5–10% of the total. This contribution increased with running speed. The arms were generally not found to contribute to drive, although considerable variation existed between subjects. Consistent with the CM results, the arms were found to reduce the changes in forward velocity of the runner rather than increasing them. It was concluded that there is no apparent advantage of the “classic” style of swinging the arms directly forward and backward over the style that most distance runners adopt of letting the arms cross over slightly in front. The crossover, in fact, helps reduce side-to-side excursions of the body CM mentioned above, hence promoting a more constant horizontal velocity.

scholarly journals A Critical Characteristic in the Transverse Galloping Pattern

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Xiaohui Wei ◽  
Yongjun Long ◽  
Chunlei Wang ◽  
Shigang Wang
Keyword(s):  
Metabolic Cost ◽  
Underlying Mechanism ◽  
Critical Value ◽  
The Body ◽  
Cost Of Transport ◽  
Leg Stiffness ◽  
Angular Velocities ◽  
The Cost ◽  
Optimal Stiffness ◽  
Transverse Galloping

Transverse gallop is a common gait used by a large number of quadrupeds. This paper employs the simplified dimensionless quadrupedal model to discuss the underlying mechanism of the transverse galloping pattern. The model is studied at different running speeds and different values of leg stiffness, respectively. If the horizontal running speed reaches up to a critical value at a fixed leg stiffness, or if the leg stiffness reaches up to a critical value at a fixed horizontal speed, a key property would emerge which greatly reduces the overall mechanical forces of the dynamic system in a proper range of initial pitch angular velocities. Besides, for each horizontal speed, there is an optimal stiffness of legs that can reduce both the mechanical loads and the metabolic cost of transport. Furthermore, different body proportions and landing distance lags of a pair of legs are studied in the transverse gallop. We find that quadrupeds with longer length of legs compared with the length of the body are more suitable to employ the transverse galloping pattern, and the landing distance lag of a pair of legs could reduce the cost of transport and the locomotion frequency.

Negligible energetic cost of sonar jamming in a bat–moth interaction

2015 ◽  
Vol 93 (4) ◽  
pp. 331-335
Author(s):  
A.J. Corcoran ◽  
H.A. Woods
Keyword(s):  
Sound Production ◽  
Resting Metabolic Rate ◽  
Metabolic Cost ◽  
Energetic Cost ◽  
Metabolic Power ◽  
Model Species ◽  
Predator Prey ◽  
Acoustic Signaling ◽  
The Subject ◽  
The Cost

Energetic cost can constrain how frequently animals exhibit behaviors. The energetic cost of acoustic signaling for communication has been the subject of numerous studies; however, the cost of acoustic signaling for predator defense has not been addressed. We studied the energetic cost and efficiency of sound production for the clicks produced by the moth Bertholdia trigona (Grote, 1879) (Grote’s bertholdia) to jam the sonar of predatory bats. This moth is an excellent model species because of its extraordinary ability to produce sound—it clicks at the highest known rate of any moth, up to 4500 clicks·s–1. We measured the metabolic cost of clicking, resting, and flying from moths suspended in a respirometry chamber. Clicking was provoked by playing back an echolocation attack sequence. The cost of sound production for B. trigona was low (66% of resting metabolic rate) and the acoustic efficiency, or the percentage of metabolic power that is converted into sound, was moderately high (0.30% ± 0.15%) compared with other species. We discuss mechanisms that allow B. trigona to achieve their extraordinary clicking rates and high acoustic efficiency. Clicking for jamming bat sonar incurs negligible energetic cost to moths despite being the most effective known anti-bat defense. These results have implications for both the ecology of predator–prey interactions and the evolution of jamming signals.

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