scholarly journals Energy-saving mechanisms in walking and running

1991 ◽  
Vol 160 (1) ◽  
pp. 55-69 ◽  
Author(s):  
R. M. Alexander
Keyword(s):  
Energy Saving ◽  
Mechanical Performance ◽  
Elastic Strain Energy ◽  
Metabolic Energy ◽  
Elastic Recoil ◽  
Work Requirements ◽  
Terrestrial Locomotion ◽  
Speed Parameter ◽  
The Relationship ◽  
Positive Work

Energy can be saved in terrestrial locomotion in many different ways. The maximum shortening speeds (Vmax) of the muscles can be adjusted to their optimum values for the tasks required of them. The moments exerted by the muscles at different joints can be adjusted to keep the ground force in line with the leg so that muscles do not work against each other. The joints of the legs can be kept as straight as possible, minimizing muscle forces and work requirements. Walking gaits should be selected at low Froude numbers (a dimensionless speed parameter) and running gaits at high Froude numbers. Tendon and other springs can be used to store elastic strain energy and to return it by elastic recoil. This paper aims to show how these energy-saving mechanisms work and to what extent mammals exploit them. Arguments based on our rather limited knowledge of the relationship between the mechanical performance of muscle and its metabolic energy consumption are used throughout. They suggest that muscles that are optimally adapted for their tasks in running should do positive work with constant efficiency.

scholarly journals A mechanical piston action may assist pelvic–pectoral fin antagonism in tree-climbing fish

2017 ◽  
Vol 98 (8) ◽  
pp. 2121-2131 ◽  
Author(s):  
Adhityo Wicaksono ◽  
Saifullah Hidayat ◽  
Bambang Retnoaji ◽  
Adolfo Rivero-Müller ◽  
Parvez Alam
Keyword(s):  
Finite Element ◽  
Energy Saving ◽  
Finite Element Simulations ◽  
Morphological Investigation ◽  
Pectoral Fin ◽  
Terrestrial Locomotion ◽  
Pectoral Fins ◽  
Biomimetic Robots ◽  
The Relationship ◽  
Pelvic Fin

In this research, we compared the anatomy and biomechanics of two species of mudskipper vs an aquatic sandgoby in view of terrestrial locomotion. Of particular interest was the relationship (if any) of pectoral fin movement with pelvic fin movement. We show that the pelvic fins of the terrestrial mudskippers studied herein, are retractable and move antagonistically with the pectoral fins. The pelvic fin of the sandgoby studied here is contrarily non-retractable and drags on any underlying substrate that the sandgoby tries to crawl across. We find that the pelvic and pectoral fin muscles of all fish are separated, but that the pectoral fins of the mudskipper species have bulkier radial muscles than the sandgoby. By coupling a detailed morphological investigation of pectoral-pelvic fins musculature with finite element simulations, we find that unlike sandgobies, the mudskipper species are able to mechanically push the pelvic fins downward as pectoral fins retract. This allows for an instant movement of pelvic fins during the pectoral fin backward stroke and as such the pelvic fins stabilize mudskippers through Stefan attachment of their pelvic fins. This mechanism seems to be efficient and energy saving and we hypothesize that the piston-like action might benefit pelvic–pectoral fin antagonism by facilitating a mechanical down-thrust. Our research on the biomechanics of tree-climbing fish provides ideas and greater potential for the development of energetically more efficient systems of ambulation in biomimetic robots.

scholarly journals Review of the relationship between aggregates geology and Los Angeles and micro-Deval tests

2021 ◽  
Vol 80 (3) ◽  
pp. 1963-1980
Author(s):  
Solomon Adomako ◽  
Christian John Engelsen ◽  
Rein Terje Thorstensen ◽  
Diego Maria Barbieri
Keyword(s):  
Los Angeles ◽  
Crystal Size ◽  
Grain Shape ◽  
Mechanical Performance ◽  
Pore Space ◽  
Construction Material ◽  
Engineering Properties ◽  
Coarse Grained ◽  
The Impact ◽  
The Relationship

AbstractRock aggregates constitute the enormous volume of inert construction material used around the globe. The petrologic description as igneous, sedimentary, and metamorphic types establishes the intrinsic formation pattern of the parent rock. The engineering properties of these rocks vary due to the differences in the transformation process (e.g. hydrothermal deposits) and weathering effect. The two most common mechanical tests used to investigate the performance of aggregates are the Los Angeles (LA) and micro-Deval (MD) tests. This study reviewed the geological parameters (including mineralogy, grain and crystal size, grain shape, and porosity) and the relationship to Los Angeles and micro-Deval tests. It was found that high content of primary minerals in rocks (e.g. quartz and feldspar) is a significant parameter for performance evaluation. Traces of secondary and accessory minerals also affect the performance of rocks, although in many cases it is based on the percentage. Furthermore, some studies showed that the effect of mineralogic composition on mechanical strength is not sufficient to draw final conclusions of mechanical performance; therefore, the impact of other textural characteristics should be considered. The disposition of grain size and crystal size (e.g. as result of lithification) showed that rocks composed of fine-grain textural composition of ≤ 1 mm enhanced fragmentation and wear resistance than medium and coarse grained (≥ 1 mm). The effect of grain shape was based on convex and concave shapes and flat and elongated apexes of tested samples. The equidimensional form descriptor of rocks somehow improved resistance to impact from LA than highly flat and elongated particles. Lastly, the distribution of pore space investigated by means of the saturation method mostly showed moderate (R = 0.50) to strong (R = 0.90) and positive correlations to LA and MD tests.

scholarly journals Modelling the elastic mechanical properties of bioactive glass-derived scaffolds

2020 ◽  
Vol 6 (1) ◽  
pp. 50-56
Author(s):  
Francesco Baino ◽  
Elisa Fiume
Keyword(s):  
Elastic Properties ◽  
Poisson’S Ratio ◽  
Mechanical Performance ◽  
Solid Material ◽  
Poisson's Ratio ◽  
Predictive Capability ◽  
Shear Moduli ◽  
Wide Range ◽  
Constitutive Parameters ◽  
The Relationship

AbstractPorosity is known to play a pivotal role in dictating the functional properties of biomedical scaffolds, with special reference to mechanical performance. While compressive strength is relatively easy to be experimentally assessed even for brittle ceramic and glass foams, elastic properties are much more difficult to be reliably estimated. Therefore, describing and, hence, predicting the relationship between porosity and elastic properties based only on the constitutive parameters of the solid material is still a challenge. In this work, we quantitatively compare the predictive capability of a set of different models in describing, over a wide range of porosity, the elastic modulus (7 models), shear modulus (3 models) and Poisson’s ratio (7 models) of bioactive silicate glass-derived scaffolds produced by foam replication. For these types of biomedical materials, the porosity dependence of elastic and shear moduli follows a second-order power-law approximation, whereas the relationship between porosity and Poisson’s ratio is well fitted by a linear equation.

Exploring the Relationship between Commitment Profiles and Work Attitudes, Employee Withdrawal, and Job Performance

2000 ◽  
Vol 29 (3) ◽  
pp. 353-366 ◽  
Author(s):  
Mark Somers ◽  
Dee Birnbaum
Keyword(s):  
Organizational Commitment ◽  
Job Performance ◽  
Job Search ◽  
Affective Commitment ◽  
Management Practice ◽  
Career Commitment ◽  
Work Attitudes ◽  
Continuance Commitment ◽  
The Relationship ◽  
Positive Work

Four commitment profiles, based on levels of commitment to the organization and the career, were used to explore the relationship between distinct patterns of commitment and work-related outcomes with a sample of professional hospital employees. As two distinct forms of organizational commitment have been identified affective and continuance commitment separate profiles were constructed for each type of organizational commitment in conjunction with career commitment. Results for profiles based on affective commitment were consistent with prior research findings, in that employees committed to both their organization and their career exhibited the most positive work attitudes and the strongest intention to remain with the organization. Unexpectedly, the dually committed also had the strongest intensity of job search behavior, but these efforts did not translate into higher incidences of turnover. No differences were observed across commitment profiles with respect to job performance. The synergistic effect between affective and career commitment was not observed for profiles based on continuance commitment to the organization. Employees committed only to their careers exhibited more positive work outcomes than did those committed only to their organizations. The implications of these findings for management practice were discussed.

scholarly journals EFFICIENCY OF PLANT IRRADIATION IN PROTECTED GROUND STRUCTURES

2019 ◽  
Vol 54 (4) ◽  
pp. 100-105
Author(s):  
R.R. Galiullin ◽  
◽  
R.S. Aipov ◽  
R.B. Yarullin ◽  
◽  
...  
Keyword(s):  
Plant Growth ◽  
Energy Saving ◽  
Growth Phase ◽  
Stem Growth ◽  
Analytic Expression ◽  
The Relationship ◽  
Ground Structures ◽  
Led Irradiation ◽  
Irradiation Facilities

The advantage of LED lamps over conventional means of plant irradiation is described. An analytic expression is proposed to determine the relationship between LED lamp characteristics and plant parameters such as the stem growth and biomass. The formula also identifies the plant growth phase, which is crucial in development of automated energy-saving LED irradiation facilities for greenhouses.

THE ENERGETIC COSTS OF CALLING IN THE BUSHCRICKET REQUENA VERTICALIS (ORTHOPTERA: TETTIGONIIDAE: LISTROSCELIDINAE)

1993 ◽  
Vol 178 (1) ◽  
pp. 21-37 ◽  
Author(s):  
W. J. Bailey ◽  
P. C. Withers ◽  
M. Endersby ◽  
K. Gaull
Keyword(s):  
Body Mass ◽  
Sound Pressure ◽  
Metabolic Cost ◽  
Acoustic Power ◽  
Metabolic Energy ◽  
Energetic Cost ◽  
Metabolic Efficiency ◽  
Metabolic Costs ◽  
Sound Pressure Levels ◽  
The Relationship

1. The metabolic costs of calling for male Requena verticalis Walker (Tettigoniidae: Listroscelidinae) were measured by direct recordings of oxygen consumption. The acoustic power output was measured by sound pressure levels around the calling bushcricket. 2. The average metabolic cost of calling was 0.143 ml g-1 h-1 but depended on calling rate. The net metabolic cost of calling per unit call, the syllable, was calculated to be 4.34×10-6+/−8.3×10-7 ml O2 syllable-1 g-1 body mass (s.e.) from the slope of the relationship between total V(dot)O2 and rate of syllable production. The resting V(dot)O2, calculated as the intercept of the relationship, was 0.248 ml O2 g-1 body mass h-1. 3. The energetic cost of calling for R. verticalis (average mass 0.37 g) was estimated at 31.85×10-6 J syllable-1. 4. Sound pressure levels were measured around calling insects. The surface area of a sphere of uniform sound pressure level [83 dB SPL root mean square (RMS) acoustic power] obtained by these measurements was used to calculate acoustic power. This was 0.20 mW. 5. The metabolic efficiency of calling, based on total metabolic energy utilisation, was 6.4 %. However, we propose that the mechanical efficiency for acoustic transmission is closer to 57 %, since only about 10 % of muscle metabolic energy is apparently available for sound production. 6. R. verticalis emits chirps formed of several syllables within which are discrete sound pulses. Wing stroke rates, when the insect is calling at its maximal rate, were approximately 583 min-1. This is slow compared to the rates observed in conehead tettigoniids, the only other group of bushcrickets where metabolic costs have been measured. The thoracic temperatures of males that had been calling for 5 min were not significantly different from those of non-calling males. 7. For R. verticalis, calling with relatively slow syllable rates may reduce the total cost of calling, and this may be a compensatory mechanism for their other high energetic cost of mating (a large spermatophylax).

External work and potential for elastic storage at the limb joints of running dogs

1998 ◽  
Vol 201 (23) ◽  
pp. 3197-3210 ◽  
Author(s):  
C. S. Gregersen ◽  
N. A. Silverton ◽  
D. R. Carrier
Keyword(s):  
Elastic Energy ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
External Work ◽  
Negative Work ◽  
Extensor Muscles ◽  
Positive Work

The storage and recovery of elastic strain energy in muscles and tendons increases the economy of locomotion in running vertebrates. In this investigation, we compared the negative and positive external work produced at individual limb joints of running dogs to evaluate which muscle-tendon systems contribute to elastic storage and to determine the extent to which the external work of locomotion is produced by muscles that shorten actively rather than by muscles that function as springs. We found that the negative and positive external work of the extensor muscles is not allocated equally among the different joints and limbs. During both trotting and galloping, the vast majority of the negative work was produced by the two distal joints, the wrist and ankle. The forelimb produced most of the negative work in both the trot and the gallop. The hindlimb produced most of the positive work during galloping, but not during trotting. With regards to elastic storage, our results indicate that the forelimb of dogs displays a greater potential for storage and recovery of elastic energy than does the hindlimb. Elastic storage appears to be more important during trotting than during galloping, and elastic storage appears to be more pronounced in the extensor muscles of the distal joints than in the extensor muscles of the proximal joints. Furthermore, our analysis indicates that a significant portion of the external work of locomotion, 26% during trotting and 56 % during galloping, is produced by actively shortening muscles. We conclude that, although elastic storage of energy is extremely important to the economy of running gaits, actively shortening muscles do make an important contribution to the work of locomotion.

Pleural stress pressure as a force to control liquid accumulation and maintain lung expansion

1985 ◽  
Vol 58 (2) ◽  
pp. 339-345 ◽  
Author(s):  
K. Harada ◽  
T. Mutsuda ◽  
N. Saoyama ◽  
N. Hamaguchi ◽  
Y. Shimada
Keyword(s):  
Chest Wall ◽  
Mean Value ◽  
Pleural Space ◽  
Liquid Volume ◽  
Parietal Pleura ◽  
Elastic Recoil ◽  
Normal Range ◽  
Pleural Surface ◽  
Lung Expansion ◽  
The Relationship

Total gas pressure in the pleural space is more subatmospheric than that in the alveolar cavity. This pressure difference minus elastic recoil pressure of the lung was termed stress pressure. We investigated the relationship between stress pressure and a force that would hold the lung against the chest wall to prevent accumulation of liquid. The condition was a pleural space with an enlarged pleural surface pressure. Dogs anesthetized with pentobarbital sodium were placed in a box maintained subatmospherically at approximately -30 cmH2O and breathed atmospheric air for 4 h. Liquid volume in the pleural space of the dogs was measured under conditions of thoracotomy. In the normal group, the volume of the pleural liquid was within the normal range of approximately 2.0 ml and the visceral and the parietal pleura made contact. In the pneumothorax group, established by injecting 50 ml of air into the pleural space, the liquid increased significantly in all cases by a mean value of approximately 12 ml. Thus pleural stress pressure seems to be an important force holding the lung against the chest wall and aiding in the control of accumulation of liquid in a more subatmospheric pleural space.

scholarly journals The Relationship Between Gait Symmetry and Metabolic Demand in Individuals With Unilateral Transfemoral Amputation: A Preliminary Study

2019 ◽  
Vol 184 (7-8) ◽  
pp. e281-e287
Author(s):  
Caitlin E Mahon ◽  
Benjamin J Darter ◽  
Christopher L Dearth ◽  
Brad D Hendershot
Keyword(s):  
Energy Expenditure ◽  
Case Series ◽  
Step Length ◽  
Metabolic Energy ◽  
Metabolic Power ◽  
Transfemoral Amputation ◽  
Preliminary Study ◽  
Spatial Asymmetries ◽  
Metabolic Energy Expenditure ◽  
The Relationship

Abstract Introduction Temporal-spatial symmetry allows for optimal metabolic economy in unimpaired human gait. The gait of individuals with unilateral transfemoral amputation is characterized by temporal-spatial asymmetries and greater metabolic energy expenditure. The objective of this study was to determine whether temporal-spatial asymmetries account for greater metabolic energy expenditure in individuals with unilateral transfemoral amputation. Materials and Methods The relationship between temporal-spatial gait asymmetry and metabolic economy (metabolic power normalized by walking speed) was retrospectively examined in eighteen individuals with transfemoral amputation walking at a self-selected velocity overground. Pearson’s product-moment correlations were used to assess the relationship between: (1) step time symmetry and metabolic economy and (2) step length symmetry and metabolic economy. The retrospective analysis of this data was approved by the Walter Reed National Military Medical Center Institutional Review Board and all individuals provided written consent. Additional insights on this relationship are presented through a case series describing the temporal-spatial and metabolic responses of two individuals with transfemoral amputation who completed a split-belt treadmill walking test. Results For the cohort of individuals, there was no significant relationship between metabolic economy and either step time asymmetry or step length asymmetry. However, the case series showed a positive relationship between step length asymmetry and metabolic power as participants adapted to split-belt treadmill walking. Conclusion There is mixed evidence for the relationship between temporal-spatial asymmetries and metabolic energy expenditure. This preliminary study may suggest optimal metabolic energy expenditure in individuals with transfemoral amputation occurs at an individualized level of symmetry and resultant deviations incur a metabolic penalty. The results of this study support the idea that addressing only temporal-spatial gait asymmetries in individuals with transfemoral amputation through rehabilitation may not improve metabolic economy. Nevertheless, future prospective research is necessary to confirm these results and implications for clinical practice.

Sign in / Sign up

Export Citation Format

Share Document