scholarly journals The work and energetic cost of locomotion. I. The effects of limb mass distribution in quadrupeds

1990 ◽  
Vol 154 (1) ◽  
pp. 273-285 ◽  
Author(s):  
K. Steudel
Keyword(s):  
Mass Distribution ◽  
Human Subjects ◽  
Center Of Mass ◽  
Qualitative Difference ◽  
Energetic Cost ◽  
Cost Of Locomotion ◽  
Rate Of Oxygen Consumption ◽  
Comparison Of The Results ◽  
The Cost ◽  
External Loads

Does limb design influence the cost of locomotion in quadrupedal mammals? If not, morphologists must dismiss the economy of locomotion from consideration when assessing the adaptive factors shaping limb structure. Several studies have recently used externally applied loads to demonstrate a relationship between limb mass distribution and energy costs in human subjects. It is not clear whether a similar correlation would hold for quadrupeds, given their very different gaits. The present study addresses this question by measuring the rate of oxygen consumption in domestic dogs running on a treadmill with mass added either to the limbs or to the back. Trials with no additional mass were used as a control. The use of externally applied loads has the advantage of allowing limb mass to be altered in a system in which other aspects of physiology that might influence cost of locomotion are held constant. The cost of adding mass to the limbs in dogs was found to be significantly greater than that of adding it at the center of mass. Limb mass distribution does affect the cost of locomotion in quadrupeds. A comparison of the results from a variety of studies in which the energetic cost of adding external loads has been measured in animals across a wide size range suggests a qualitative difference in the factors determining the cost of locomotion in large and small animals.

The work and energetic cost of locomotion. II. Partitioning the cost of internal and external work within a species

1990 ◽  
Vol 154 (1) ◽  
pp. 287-303 ◽  
Author(s):  
K. Steudel
Keyword(s):  
Center Of Mass ◽  
Elastic Strain Energy ◽  
Mechanical Work ◽  
Metabolic Energy ◽  
Energetic Cost ◽  
External Work ◽  
Internal Work ◽  
Cost Of Locomotion ◽  
Large Animals ◽  
The Cost

Previous studies have shown that large animals have systematically lower mass-specific costs of locomotion than do smaller animals, in spite of there being no demonstrable difference between them in the mass-specific mechanical work of locomotion. Larger animals are somehow much more efficient at converting metabolic energy to mechanical work. The present study analyzes how this decoupling of work and cost might occur. The experimental design employs limb-loaded and back-loaded dogs and allows the energetic cost of locomotion to be partitioned between that used to move the center of mass (external work) and that used to move the limbs relative to the center of mass (internal work). These costs were measured in three dogs moving at four speeds. Increases in the cost of external work with speed parallel increases in the amount of external work based on data from previous studies. However, increases in the cost of internal work with speed are much less (less than 50%) than the increase in internal work itself over the speeds examined. Furthermore, the cost of internal work increases linearly with speed, whereas internal work itself increases as a power function of speed. It is suggested that this decoupling results from an increase with speed in the extent to which the internal work of locomotion is powered by non-metabolic means, such as elastic strain energy and transfer of energy within and between body segments.

scholarly journals Effect of limb mass and its distribution on the energetic cost of running

1985 ◽  
Vol 116 (1) ◽  
pp. 363-373 ◽  
Author(s):  
M. J. Myers ◽  
K. Steudel
Keyword(s):  
Energy Consumption ◽  
Human Subjects ◽  
Energetic Cost ◽  
Centre Of Mass ◽  
Important Constraint ◽  
Cost Of Locomotion ◽  
The Cost ◽  
Limb Structure ◽  
Selection Of ◽  
Limb Morphology

Functional morphologists have traditionally regarded cost of locomotion as an important influence on the design of locomotor structures. If cost of locomotion is an important constraint in the natural selection of these structures, it should be possible to show that animals differing in limb morphology also differ in their locomotor costs. In previous experiments on three species of cursorial mammals differing considerably in limb structure, no such differences were detected. Since the factors that determine the rate of energy consumption of a running animal are not well understood, we felt that the effect of limb morphology on cost could best be examined in a system in which only the inertial properties of limbs were varied while other factors remained constant. Consequently, we have measured changes in the rate of energy consumption of running human subjects produced by artificial alterations in limb inertial properties. Other variables that might influence cost have been controlled. We found that the cost of adding a given mass to the limbs is significantly greater than adding it to the centre of mass and that this effect becomes more pronounced as the limb loads are moved distally. Thus a clear effect of limb mass and its distribution on cost of locomotion has been demonstrated.

Speed, stride frequency and energy cost per stride: how do they change with body size and gait?

1988 ◽  
Vol 138 (1) ◽  
pp. 301-318 ◽  
Author(s):  
N. C. Heglund ◽  
C. R. Taylor
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Energy Cost ◽  
Reaction Force ◽  
Stride Frequency ◽  
Energetic Cost ◽  
Published Data ◽  
Frequency Change ◽  
Cost Of Locomotion ◽  
The Cost

In this study we investigate how speed and stride frequency change with body size. We use this information to define ‘equivalent speeds’ for animals of different size and to explore the factors underlying the six-fold difference in mass-specific energy cost of locomotion between mouse- and horse-sized animals at these speeds. Speeds and stride frequencies within a trot and a gallop were measured on a treadmill in 16 species of wild and domestic quadrupeds, ranging in body size from 30 g mice to 200 kg horses. We found that the minimum, preferred and maximum sustained speeds within a trot and a gallop all change in the same rather dramatic manner with body size, differing by nine-fold between mice and horses (i.e. all three speeds scale with about the 0.2 power of body mass). Although the absolute speeds differ greatly, the maximum sustainable speed was about 2.6-fold greater than the minimum within a trot, and 2.1-fold greater within a gallop. The frequencies used to sustain the equivalent speeds (with the exception of the minimum trotting speed) scale with about the same factor, the −0.15 power of body mass. Combining this speed and frequency data with previously published data on the energetic cost of locomotion, we find that the mass-specific energetic cost of locomotion is almost directly proportional to the stride frequency used to sustain a constant speed at all the equivalent speeds within a trot and a gallop, except for the minimum trotting speed (where it changes by a factor of two over the size range of animals studied). Thus the energy cost per kilogram per stride at five of the six equivalent speeds is about the same for all animals, independent of body size, but increases with speed: 5.0 J kg-1 stride-1 at the preferred trotting speed; 5.3 J kg-1 stride-1 at the trot-gallop transition speed; 7.5 J kg-1 stride-1 at the preferred galloping speed; and 9.4 J kg-1 stride-1 at the maximum sustained galloping speed. The cost of locomotion is determined primarily by the cost of activating muscles and of generating a unit of force for a unit of time. Our data show that both these costs increase directly with the stride frequency used at equivalent speeds by different-sized animals. The increase in cost per stride with muscles (necessitating higher muscle forces for the same ground reaction force) as stride length increases both in the trot and in the gallop.

Moving cheaply: energetics of walking in the African elephant.

1995 ◽  
Vol 198 (3) ◽  
pp. 629-632 ◽  
Author(s):  
V A Langman ◽  
T J Roberts ◽  
J Black ◽  
G M Maloiy ◽  
N C Heglund ◽  
...  
Keyword(s):  
Fuel Economy ◽  
African Elephant ◽  
Metabolic Energy ◽  
Energetic Cost ◽  
Allometric Relationships ◽  
Cost Of Locomotion ◽  
Biological Laws ◽  
Large Animals ◽  
The Cost

Large animals have a much better fuel economy than small ones, both when they rest and when they run. At rest, each gram of tissue of the largest land animal, the African elephant, consumes metabolic energy at 1/20 the rate of a mouse; using existing allometric relationships, we calculate that it should be able to carry 1 g of its tissue (or a load) for 1 km at 1/40 the cost for a mouse. These relationships between energetics and size are so consistent that they have been characterized as biological laws. The elephant has massive legs and lumbers along awkwardly, suggesting that it might expend more energy to move about than other animals. We find, however, that its energetic cost of locomotion is predicted remarkably well by the allometric relationships and is the lowest recorded for any living land animal.

Energetic Cost of Running with different Muscle Temperatures in Savannah MOnitor Lizards

1982 ◽  
Vol 99 (1) ◽  
pp. 269-277
Author(s):  
LAWRENCE C. ROME
Keyword(s):  
Isometric Force ◽  
Stride Frequency ◽  
Energetic Cost ◽  
Muscle Temperature ◽  
Apparent Difference ◽  
Muscle Energetics ◽  
Cost Of Locomotion ◽  
Monitor Lizards ◽  
The Cost

The purpose of this study was to determine whether the energetic cost of locomotion was independent of muscle temperature, or if it tripled with a 10 °C increase in temperature, like the cost of generating isometric force in isolated muscle preparations. For a given running speed of Savannah Monitor lizards, the energetic cost of locomotion (the difference between running and resting metabolism) was the same when muscle temperature was 28.5 °C as when it was 38 °C. It was also found that stride frequency and posture did not change with temperature, indicating that the average force exerted by the lizards' muscles during locomotion at the two temperatures was the same. This suggests that the cost of generating force in vivo is independent of temperature. Several possible explanations of the apparent difference between in vivo and in vitro muscle energetics are discussed.

Energetics of ascent: insects on inclines

1990 ◽  
Vol 149 (1) ◽  
pp. 307-317 ◽  
Author(s):  
R. J. Full ◽  
A. Tullis
Keyword(s):  
Oxygen Consumption ◽  
Minimum Cost ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Stride Frequency ◽  
Energetic Cost ◽  
Incline Angle ◽  
Small Animals ◽  
Cost Of Locomotion ◽  
The Cost

Small animals use more metabolic energy per unit mass than large animals to run on a level surface. If the cost to lift one gram of mass one vertical meter is constant, small animals should require proportionally smaller increases in metabolic cost to run uphill. To test this hypothesis on very small animals possessing an exceptional capacity for ascending steep gradients, we measured the metabolic cost of locomotion in the cockroach, Periplaneta americana, running at angles of 0, 45 and 90 degrees to the horizontal. Resting oxygen consumption (VO2rest) was not affected by incline angle. Steady-state oxygen consumption (VO2ss) increased linearly with speed at all angles of ascent. The minimum cost of locomotion (the slope of the VO2ss versus speed function) increased with increasing angle of ascent. The minimum cost of locomotion on 45 and 90 degrees inclines was two and three times greater, respectively, than the cost during horizontal running. The cockroach's metabolic cost of ascent greatly exceeds that predicted from the hypothesis of a constant efficiency for vertical work. Variations in stride frequency and contact time cannot account for the high metabolic cost, because they were independent of incline angle. An increase in the metabolic cost or amount of force production may best explain the increase in metabolic cost. Small animals, such as P. americana, can easily scale vertical surfaces, but the energetic cost is considerable.

scholarly journals Scaling of muscle fibres and locomotion

1992 ◽  
Vol 168 (1) ◽  
pp. 243-252 ◽  
Author(s):  
L. C. Rome
Keyword(s):  
Muscle Fibre ◽  
Body Mass ◽  
Fibre Type ◽  
Fibre Types ◽  
Energetic Cost ◽  
Muscle Fibres ◽  
Small Animals ◽  
Running Speed ◽  
Cost Of Locomotion ◽  
The Cost

To reconcile the scaling of the mechanics and energetics of locomotion to recent data on the scaling of the mechanics of muscle fibres, I have extended the theory of Taylor and colleagues that the energetic cost of locomotion is determined by the cost of generating force by the fibres. By assuming (1) that the cost of generating force in a fibre is proportional to V(max) (maximum velocity of shortening) and (2) that, at physiologically equivalent speeds, animals of different body sizes recruit the same fibre types, this extension quantitatively predicts the scaling of the energetics of locomotion, as well as other observations, from the scaling of V(max) of the muscle fibres. First, the energetic cost of locomotion at physiologically equivalent speeds scales with Mb-0.16, where Mb is body mass, as does V(max) of a given fibre type. However, the energetic cost at absolute speeds (cost of transport) scales with Mb-0.30, because small animals must compress their recruitment order into a narrower speed range and, hence, recruit faster muscle fibre types at a given running speed. Thus, it costs more for small animals to move 1 kg of their body mass 1 km not only because a given muscle fibre type from a small animal costs more to generate force than from a large one, but also because small animals recruit faster fibre types at a given absolute running speed. In addition, this analysis provides evidence that V(max) scales similarly to 1/tc (where tc is foot contact time) and muscle shortening velocity (V), in agreement with recent models. Finally, this extension predicts that, at physiologically equivalent speeds, the weight-specific energetic cost per step is independent of body size, as has been found empirically.

scholarly journals Amelioration of the Cost of Conjugative Plasmid Carriage in Eschericha coli K12

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 1641-1649
Author(s):  
Cecilia Dahlberg ◽  
Lin Chao
Keyword(s):  
Drug Resistance ◽  
Multiple Drug Resistance ◽  
Conjugative Plasmid ◽  
Energetic Cost ◽  
Multiple Drug ◽  
Genetic Changes ◽  
Batch Cultures ◽  
Transfer Rates ◽  
Bacterial Plasmid ◽  
The Cost

Abstract Although plasmids can provide beneficial functions to their host bacteria, they might confer a physiological or energetic cost. This study examines how natural selection may reduce the cost of carrying conjugative plasmids with drug-resistance markers in the absence of antibiotic selection. We studied two plasmids, R1 and RP4, both of which carry multiple drug resistance genes and were shown to impose an initial fitness cost on Escherichia coli. To determine if and how the cost could be reduced, we subjected plasmid-containing bacteria to 1100 generations of evolution in batch cultures. Analysis of the evolved populations revealed that plasmid loss never occurred, but that the cost was reduced through genetic changes in both the plasmids and the bacteria. Changes in the plasmids were inferred by the demonstration that evolved plasmids no longer imposed a cost on their hosts when transferred to a plasmid-free clone of the ancestral E. coli. Changes in the bacteria were shown by the lowered cost when the ancestral plasmids were introduced into evolved bacteria that had been cured of their (evolved) plasmids. Additionally, changes in the bacteria were inferred because conjugative transfer rates of evolved R1 plasmids were lower in the evolved host than in the ancestral host. Our results suggest that once a conjugative bacterial plasmid has invaded a bacterial population it will remain even if the original selection is discontinued.

scholarly journals Limitations imposed by wearing armour on Medieval soldiers' locomotor performance

2011 ◽  
Vol 279 (1729) ◽  
pp. 640-644 ◽  
Author(s):  
Graham N. Askew ◽  
Federico Formenti ◽  
Alberto E. Minetti
Keyword(s):  
Fifteenth Century ◽  
Physical Performance ◽  
Energy Use ◽  
Steel Plate ◽  
Energetic Cost ◽  
Entire Body ◽  
Additional Mass ◽  
Medieval Europe ◽  
Cost Of Locomotion ◽  
Locomotor Energetics

In Medieval Europe, soldiers wore steel plate armour for protection during warfare. Armour design reflected a trade-off between protection and mobility it offered the wearer. By the fifteenth century, a typical suit of field armour weighed between 30 and 50 kg and was distributed over the entire body. How much wearing armour affected Medieval soldiers' locomotor energetics and biomechanics is unknown. We investigated the mechanics and the energetic cost of locomotion in armour, and determined the effects on physical performance. We found that the net cost of locomotion ( C met ) during armoured walking and running is much more energetically expensive than unloaded locomotion. C met for locomotion in armour was 2.1–2.3 times higher for walking, and 1.9 times higher for running when compared with C met for unloaded locomotion at the same speed. An important component of the increased energy use results from the extra force that must be generated to support the additional mass. However, the energetic cost of locomotion in armour was also much higher than equivalent trunk loading. This additional cost is mostly explained by the increased energy required to swing the limbs and impaired breathing. Our findings can predict age-associated decline in Medieval soldiers' physical performance, and have potential implications in understanding the outcomes of past European military battles.

An Experiment in Problem Solving

1951 ◽  
Vol 3 (4) ◽  
pp. 184-197 ◽  
Author(s):  
J. W. Whitfield
Keyword(s):  
Problem Solving ◽  
Experimental Work ◽  
Human Subjects ◽  
Qualitative Difference ◽  
Trial And Error ◽  
Qualitative Nature ◽  
The Individual

Trial-and-error problems are described in terms of “stimulus” difficulty, which is a measure of the number of possible modes of response left to the individual when all the information given is taken into account; and “phenomenal” difficulty, which is a measure derived from the individual's performance. An experiment is described in which three types of problem were presented to human subjects. In all three problems the stimulus difficulty was calculable, stage by stage, in the solution. The problems differed in this stimulus difficulty and also in the qualitative nature of the information provided—from unequivocal to conditional. It is shown that the qualitative difference of the nature of the information bears most relationship to phenomenal difficulty. Some observations are made on the modes of solution adopted, and further experimental work is suggested.

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