scholarly journals The changes in power requirements and muscle efficiency during elevated force production in the fruit fly Drosophila melanogaster.

1997 ◽  
Vol 200 (7) ◽  
pp. 1133-1143 ◽  
Author(s):  
F O Lehmann ◽  
M H Dickinson
Keyword(s):  
Drosophila Melanogaster ◽  
Power Output ◽  
Force Production ◽  
Fruit Fly ◽  
Reynolds Numbers ◽  
Power Input ◽  
Mechanical Power ◽  
Total Power ◽  
Mechanical Power Output ◽  
The Cost

The limits of flight performance have been estimated in tethered Drosophila melanogaster by modulating power requirements in a 'virtual reality' flight arena. At peak capacity, the flight muscles can sustain a mechanical power output of nearly 80 W kg-1 muscle mass at 24 degrees C, which is sufficient to generate forces of approximately 150% of the animal's weight. The increase in flight force above that required to support body weight is accompanied by a rise in wing velocity, brought about by an increase in stroke amplitude and a decrease in stroke frequency. Inertial costs, although greater than either profile or induced power, would be minimal with even modest amounts of elastic storage, and total mechanical power energy should be equivalent to aerodynamic power alone. Because of the large profile drag expected at low Reynolds numbers, the profile power was approximately twice the induced power at all levels of force generation. Thus, it is the cost of overcoming drag, and not the production of lift, that is the primary requirement for flight in Drosophila melanogaster. By comparing the estimated mechanical power output with respirometrically measured total power input, we determined that muscle efficiency rises with increasing force production to a maximum of 10%. This change in efficiency may reflect either increased crossbridge activation or a favorable strain regime during the production of peak forces.

Mechanical and propelling efficiency in swimming derived from exercise using a laboratory-based whole-body swimming ergometer

2012 ◽  
Vol 113 (4) ◽  
pp. 584-594 ◽  
Author(s):  
Paola Zamparo ◽  
Ian L. Swaine
Keyword(s):  
Power Output ◽  
Power Input ◽  
Mechanical Power ◽  
Whole Body ◽  
Metabolic Power ◽  
Exact Simulation ◽  
Mechanical Power Output ◽  
Propelling Efficiency ◽  
Overall Efficiency ◽  
Active Drag

Determining the efficiency of a swimming stroke is difficult because different “efficiencies” can be computed based on the partitioning of mechanical power output (Ẇ) into its useful and nonuseful components, as well as because of the difficulties in measuring the forces that a swimmer can exert in water. In this paper, overall efficiency (ηO = ẆTOT/Ė, where ẆTOT is total mechanical power output, and Ė is overall metabolic power input) was calculated in 10 swimmers by means of a laboratory-based whole-body swimming ergometer, whereas propelling efficiency (ηP = ẆD/ẆTOT, where ẆD is the power to overcome drag) was estimated based on these values and on values of drag efficiency (ηD = ẆD/Ė): ηP = ηD/ηO. The values of ηD reported in the literature range from 0.03 to 0.09 (based on data for passive and active drag, respectively). ηO was 0.28 ± 0.01, and ηP was estimated to range from ∼0.10 (ηD = 0.03) to 0.35 (ηD = 0.09). Even if there are obvious limitations to exact simulation of the whole swimming stroke within the laboratory, these calculations suggest that the data reported in the literature for ηO are probably underestimated, because not all components of ẆTOT can be measured accurately in this environment. Similarly, our estimations of ηP suggest that the data reported in the literature are probably overestimated.

scholarly journals GENETIC VARIABILITY OF FLIGHT METABOLISM IN DROSOPHILA MELANOGASTER. II. RELATIONSHIP BETWEEN POWER OUTPUT AND ENZYME ACTIVITY LEVELS

Genetics ◽  
1985 ◽  
Vol 111 (4) ◽  
pp. 845-868
Author(s):  
C C Laurie-Ahlberg ◽  
P T Barnes ◽  
J W Curtsinger ◽  
T H Emigh ◽  
B Karlin ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Power Output ◽  
Mechanical Power ◽  
Activity Levels ◽  
Substitution Lines ◽  
Wingbeat Frequency ◽  
Metabolism Enzymes ◽  
Mechanical Power Output ◽  
Flight Metabolism ◽  
Flight Muscles

ABSTRACT The major goal of the studies reported here was to determine the extent to which genetic variation in the activities of the enzymes participating in flight metabolism contributes to variation in the mechanical power output of the flight muscles in Drosophila melanogaster. Isogenic chromosome substitution lines were used to partition the variance of both types of quantitative trait into genetic and environmental components. The mechanical power output was estimated from the wingbeat frequency, wing amplitude and wing morphology of tethered flies by applying the aerodynamic models of Weis-Fogh and Ellington. There were three major results. (1) Chromosomes sampled from natural populations provide a large and repeatable genetic component to the variation in the activities of most of the 15 flight metabolism enzymes investigated and to the variation in the mechanical power output of the flight muscles. (2) The mechanical power output is a sensitive indicator of the rate of flight metabolism (i.e., rate of oxygen consumption during tethered flight). (3) In spite of (1) and (2), no convincing cases of individual enzyme effects on power output were detected, although the number and sign of the significant enzyme-power correlations suggests that such effects are not totally lacking.

The efficiency of an asynchronous flight muscle from a beetle

2001 ◽  
Vol 204 (23) ◽  
pp. 4125-4139 ◽  
Author(s):  
Robert K. Josephson ◽  
Jean G. Malamud ◽  
Darrell R. Stokes
Keyword(s):  
Stimulus Intensity ◽  
Power Output ◽  
Flight Muscle ◽  
Power Input ◽  
Mechanical Power ◽  
Co2 Production ◽  
Time Range ◽  
Metabolic Power ◽  
Mechanical Power Output ◽  
Flight Muscles

SUMMARYMechanical power output and metabolic power input were measured from an asynchronous flight muscle, the basalar muscle of the beetle Cotinus mutabilis. Mechanical power output was determined using the work loop technique and metabolic power input by monitoring CO2 production or both CO2 production and O2 consumption. At 35°C, and with conditions that maximized power output (60 Hz sinusoidal strain, optimal muscle length and strain amplitude, 60 Hz stimulation frequency), the peak mechanical power output during a 10 s burst was approximately 140 W kg–1, the respiratory coefficient 0.83 and the muscle efficiency 14–16 %. The stimulus intensity used was the minimal required to achieve a maximal isometric tetanus. Increasing or decreasing the stimulus intensity from this level changed mechanical power output but not efficiency, indicating that the efficiency measurements were not contaminated by excitation of muscles adjacent to that from which the mechanical recordings were made. The CO2 produced during an isometric tetanus was approximately half that during a bout of similar stimulation but with imposed sinusoidal strain and work output, suggesting that up to 50 % of the energy input may go to muscle activation costs. Reducing the stimulus frequency to 30 Hz from its usual value of 60 Hz reduced mechanical power output but had no significant effect on efficiency. Increasing the frequency of the sinusoidal strain from 60 to 90 Hz reduced power output but not CO2 consumption; hence, there was a decline in efficiency. The respiratory coefficient was the same for 10 s and 30 s bursts of activity, suggesting that there was no major change in the fuel used over this time range.The mass-specific mechanical power output and the efficiency of the beetle muscle were each 2–3 times greater than values measured in previous studies, using similar techniques, from locust flight muscles, which are synchronous muscles. These results support the hypothesis that asynchronous flight muscles have evolved in several major insect taxa because they can provide greater power output and are more efficient than are synchronous muscles for operation at the high frequencies of insect flight.

Hummingbird hovering performance in hyperoxic heliox: effects of body mass and sex.

1996 ◽  
Vol 199 (12) ◽  
pp. 2745-2755 ◽  
Author(s):  
P Chai ◽  
R Harrykissoon ◽  
R Dudley
Keyword(s):  
Power Output ◽  
Aerodynamic Force ◽  
Force Production ◽  
Power Input ◽  
Flight Mechanics ◽  
Flight Performance ◽  
Metabolic Power ◽  
Significant Extent ◽  
Mechanical Power Output ◽  
Stroke Amplitude

Owing to their small size and hovering locomotion, hummingbirds are the most aerobically active vertebrate endotherms. Can hyperoxia enhance the flight performance of this highly oxygen-dependent group? Hovering performance of ruby-throated hummingbirds (Archilochus colubris) was manipulated non-invasively using hyperoxic but hypodense gas mixtures of sea-level air combined with heliox containing 35% O2. This manipulation sheds light on the interplay among metabolic power input, mechanical power output and aerodynamic force production in limiting flight performance. No significant differences in flight mechanics and oxygen consumption were identified between hyperoxic and normoxic conditions. Thus, at least in the present experimental context, hyperoxia did not change the major metabolic and mechanical parameters; O2 diffusive capacities of the respiratory system were probably not limiting to a significant extent. Compared with hummingbirds in our previous studies, the present experimental birds were heavier, had resultant shorter hover-feeding durations and experienced aerodynamic failure at higher air densities. Because hummingbirds have relatively stable wingbeat frequencies, modulation of power output was attained primarily through variation in stroke amplitude up to near 180 degrees. This result indicates that maximum hovering performance was constrained geometrically and that heavier birds with greater fat loads had less margin for enhancement of power production. Sexual dimorphism in flight adaptation also played a role, with males showing more limited hovering capacities, presumably as a trade-off for increased maneuverability.

A Comparison of Mechanical and Energetic Estimates of Flight Cost for Hovering Sphinx Moths

1981 ◽  
Vol 91 (1) ◽  
pp. 117-129 ◽  
Author(s):  
TIMOTHY M. CASEY
Keyword(s):  
Body Mass ◽  
Power Output ◽  
Power Input ◽  
Flight Mechanics ◽  
Mechanical Power ◽  
Specific Power ◽  
Power Requirement ◽  
Power Cost ◽  
Mechanical Power Output ◽  
Specific Power Input

Mechanical power output, based on measured power input, is compared with calculated values for aerodynamic and inertial power output in sphinx moths ranging from 350 to 3400 mg. Aerodynamic power output, calculated from momentum and blade-element aerodynamic theories, scales with the 1.08 power of body mass, amounting to about 40% of the mechanical power output of large moths to about 15% in the smallest individuals. Calculated value for the inertial power cost of hovering represents a larger fraction of the mechanical power output than the aerodynamic cost in all moths, with the value increasing as body mass decreases. Independent estimates of inertial power output based on metabolic data are similar to those obtained from calculations of the moment of inertia for the wings. These data suggest that inertial power output represents the largest power requirement for hovering sphinx moths, and that elastic torques do not significantly reduce the mechanical power output. Higher mass-specific power input of small sphinx moths appears to be the result of greater mass-specific inertial power requirements. Estimates of flight cost based on morphology and flight mechanics of sphinx moths yield values for mechanical power output which are similar to values estimated from their flight metabolism.

Flight Energetics of Euglossine Bees in Relation to Morphology and Wing Stroke Frequency

1985 ◽  
Vol 116 (1) ◽  
pp. 271-289 ◽  
Author(s):  
TIMOTHY M. CASEY ◽  
MICHAEL L. MAY ◽  
KENNETH R. MORGAN
Keyword(s):  
Energy Metabolism ◽  
Body Mass ◽  
Power Output ◽  
Power Input ◽  
Mechanical Power ◽  
Euglossine Bees ◽  
Stroke Frequency ◽  
Dynamic Power ◽  
Mechanical Power Output ◽  
Wing Stroke

Mass-specific oxygen consumption of euglossine bees during free hove ringflight is inversely related to body mass, varying from 66 mlO2 g−1 h−1 in a 1.0 -g bee to 154 mlO2 g−1 h−1 in a 0.10 -g bee. Individuals of Eulaema and Eufreisea spp. have smaller wings and higher wing stroke frequency and energy metabolism at any given mass than bees of Euglossa spp. or Exaeretefrontalis. Calculated aero dynamic power requirements represent only a small fraction of the energy metabolism, and apparent flight efficiency aero dynamic power (= induced + profile power)/power input decreases as sizedeclines. If efficiency of flight muscle = 0.2, the mechanical power output of hovering bees varies inversely with body mass from about 480 to 1130 W kg−1 of muscle. These values are 1.9 to 4.5 times greater than previous predictions of maximum mechanical power output (Weis-Fogh & Alexander, 1977; see also Ellington, 1984c). Mass-specific energy expenditure per wing stroke is independent of body mass and essentially the same for all euglossines. Differences in energy metabolism among bees having similar body mass isprimarily related to differences in wing stroke frequency. Scaling of energy metabolism in relation to mass is generally similar to the relationship for sphingid moths despite the fact that bees have asynchronous flight musclewhereas moths have synchronous muscle.

DIVING ENERGETICS IN LESSER SCAUP (AYTHYTA AFFINIS, EYTON)

1994 ◽  
Vol 190 (1) ◽  
pp. 155-178 ◽  
Author(s):  
R Stephenson
Keyword(s):  
Power Output ◽  
Power Input ◽  
Dominant Factor ◽  
Buoyant Force ◽  
Biomechanical Models ◽  
Drag Forces ◽  
Lesser Scaup ◽  
Mechanical Power Output ◽  
Recovery Stroke ◽  
The Cost

Mechanical and aerobic energy costs of diving were measured simultaneously by closed-circuit respirometry in six lesser scaup Aythya affinis Eyton (body mass=591±30 g) during bouts of voluntary feeding dives. Durations of dives (td=13.5±1.4 s) and surface intervals (ti=16.3±2.2 s) were within the normal range for ducks diving to 1.5 m depth. Mechanical power output (3.69±0.24 W kg-1) and aerobic power input (29.32±2.47 W kg-1) were both higher than previous estimates. Buoyancy was found to be the dominant factor determining dive costs, contributing 62 % of the mechanical cost of descent and 87 % of the cost of staying at the bottom while feeding. Drag forces, including the contribution from the forward-moving hindlimbs during the recovery stroke of the leg-beat cycle, contributed 27 % and 13 % of the mechanical costs of descent and feeding, respectively. Inertial forces created by net acceleration during descent contributed approximately 11 % during descent but not at all during the feeding phase. Buoyant force at the start of voluntary dives (6.2±0.35 N kg-1) was significantly greater than that measured in restrained ducks (4.9±0.2 N kg-1). Loss of air from the plumage layer and compression due to hydrostatic pressure decreased buoyancy by 32 %. Mechanical work and power output were 1.9 and 2.4 times greater during descent than during the feeding phase. Therefore, energetic costs are strongly affected by dive-phase durations. Estimates by unsteady and steady biomechanical models differ significantly during descent but not during the feeding phase.

scholarly journals Power and efficiency of insect flight muscle

1985 ◽  
Vol 115 (1) ◽  
pp. 293-304 ◽  
Author(s):  
C. P. Ellington
Keyword(s):  
Power Output ◽  
Flight Muscle ◽  
Insect Flight ◽  
Power Input ◽  
Mechanical Power ◽  
Insect Flight Muscle ◽  
Muscle Properties ◽  
System A ◽  
Mechanical Power Output ◽  
Flight Muscles

The efficiency and mechanical power output of insect flight muscle have been estimated from a study of hovering flight. The maximum power output, calculated from the muscle properties, is adequate for the aerodynamic power requirements. However, the power output is insufficient to oscillate the wing mass as well unless there is good elastic storage of the inertial energy, and this is consistent with reports of elastic components in the flight system. A comparison of the mechanical power output with the metabolic power input to the flight muscles suggests that the muscle efficiency is quite low: less than 10%.

The efficiency of frog ventricular muscle.

1994 ◽  
Vol 197 (1) ◽  
pp. 143-164
Author(s):  
D A Syme
Keyword(s):  
Power Output ◽  
Muscle Length ◽  
Length Change ◽  
Mechanical Power ◽  
Muscle Fibres ◽  
Cycle Frequency ◽  
Energy Equivalent ◽  
Mechanical Power Output ◽  
Loop Technique ◽  
The Cost

Mechanical power and oxygen consumption (VO2) were measured simultaneously from isolated segments of trabecular muscle from the frog (Rana pipiens) ventricle. Power was measured using the work-loop technique, in which bundles of trabeculae were subjected to cyclic, sinusoidal length change and phasic stimulation. VO2 was measured using a polarographic O2 electrode. Both mechanical power and VO2 increased with increasing cycle frequency (0.4-0.9 Hz), with increasing muscle length and with increasing strain (= shortening, range 0-25% of resting length). Net efficiency, defined as the ratio of mechanical power output to the energy equivalent of the increase in VO2 above resting level, was independent of cycle frequency and increased from 8.1 to 13.0% with increasing muscle length, and from 0 to 13% with increasing strain, in the ranges examined. Delta efficiency, defined as the slope of the line relating mechanical power output to the energy equivalent of VO2, was 24-43%, similar to that reported from studies using intact hearts. The cost of increasing power output was greater if power was increased by increasing cycle frequency or muscle length than if it was increased by increasing strain. The results suggest that the observation that pressure-loading is more costly than volume-loading is inherent to these muscle fibres and that frog cardiac muscle is, if anything, less efficient than most skeletal muscles studied thus far.

scholarly journals On the mechanical power output comparisons of cone dielectric elastomer actuators

2021 ◽  
pp. 1-1
Author(s):  
Chongjing Cao ◽  
Lijin Chen ◽  
Wenke Duan ◽  
Thomas L. Hill ◽  
Bo Li ◽  
...  
Keyword(s):  
Power Output ◽  
Dielectric Elastomer ◽  
Mechanical Power ◽  
Dielectric Elastomer Actuators ◽  
Mechanical Power Output
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