scholarly journals Contraction Dynamics of Flight and Stridulatory Muscles of Tettigoniid Insects

1984 ◽  
Vol 108 (1) ◽  
pp. 77-96 ◽  
Author(s):  
ROBERT K. JOSEPHSON
Keyword(s):  
Isometric Contraction ◽  
Time Course ◽  
Published Data ◽  
Shortening Velocity ◽  
Stroke Frequency ◽  
Thoracic Temperature ◽  
Force Velocity ◽  
Contraction Kinetics ◽  
Wing Stroke ◽  
Tetanic Tension

1. Isometric contraction kinetics and force-velocity relations were examined in wing muscles of two tettigoniid insects, Neoconocephalus robustus and N. triops. The muscles were first tergocoxal muscles of the mesothoracic and metathoracic segments. The metathoracic muscle is a flight muscle. The mesothoracic muscle is used in flight and in stridulation. 2. In the field, the wing stroke frequency during stridulation by N. triops is about 100 Hz; the thoracic temperature during singing is about 30 C; and the temperature gradient between the thorax and surround is about 15 C. Published data for N. robustus give the wing-stroke frequency during stridulation as about 200 Hz at a thoracic temperature of 35–40 C. The wing-stroke frequency during flight by both species is approximately 20 Hz at 25 C. 3. The twitch time course is similar in equivalent muscles of the two species. At 35 C the twitch duration (onset to 50% relaxation) is 5.5-6.5 ms for mesothoracic muscles and 11–13 ms for metathoracic ones. Twitch and tetanic tension per unit area are about twice as great in the metathoracic muscles as in the faster, mesothoracic ones. 4. Despite the differences in isometric contraction kinetics, the maximum shortening velocity (Vmax) is similar in mesothoracic and metathoracic wing muscles. Vmax values (lengths per second, 35 C), determined by extrapolation of force-velocity curves, were 10.1 (mesothoracic) and 11.1 (metathoracic) for N. robustus; 12.2 (mesothoracic) and 16.1 (metathoracic) for N. triops. With N. triops, Vmax was also determined from the time taken to re-develop tension following quick release. The values obtained were somewhat higher than from extrapolation of force-velocity curves, but again similar for mesothoracic and metathoracic muscles. 5. Twitch time course becomes more rapid and Vmax increases with increasing temperature. Neither twitch nor tetanic tension is greatly affected by temperature change in the range 25–35 C. 6. As for many other fast muscles, force-velocity plots for these muscles have little curvature. It is suggested that the relative straightness of these plots is a consequence of internal viscosity.

scholarly journals A phenomenological model of the time course of maximal voluntary isometric contraction force for optimization of complex loading schemes

2018 ◽  
Author(s):  
Johannes L. Herold ◽  
Christian Kirches ◽  
Johannes P. Schlöder
Keyword(s):  
Isometric Contraction ◽  
Time Course ◽  
Complex Loading ◽  
Equation Model ◽  
Limiting Factor ◽  
Published Data ◽  
Ordinary Differential Equation Model ◽  
Differential Equation Model ◽  
Maximal Voluntary Isometric Contraction ◽  
Time Courses

AbstractWe construct a simple and predictive ordinary differential equation model to describe the time course of maximal voluntary isometric contraction (MVIC) force during voluntary isometric contractions and at rest. These time courses are of particular interest whenever force capacities are a limiting factor, e.g. during heavy manual work or resistance training (RT) sessions. Our model is able to describe MVIC force under complex loading schemes and is validated with a comprehensive set of published data from the elbow flexors. We use the calibrated model to analyze fatigue and recovery patterns observed in the literature. Due to the model’s structure, it can be efficiently employed to optimize complex loading schemes. We demonstrate this by computing a work-rest schedule that minimizes fatigue and an optimal isometric RT session as examples.

Mechanical properties of pulmonary arteries from sensitized dogs

1983 ◽  
Vol 55 (6) ◽  
pp. 1669-1673 ◽  
Author(s):  
S. K. Kong ◽  
N. L. Stephens
Keyword(s):  
Mechanical Properties ◽  
Pulmonary Arteries ◽  
Maximal Velocity ◽  
Shortening Velocity ◽  
Littermate Control ◽  
Velocity Of Shortening ◽  
Force Velocity ◽  
Tetanic Tension ◽  
Isotonic Shortening

On the basis of isometric dose-response studies, we (J. Pharmacol. Exp. Ther. 219:551-557, 1981) have reported that the ovalbumin-sensitized (S) canine pulmonary artery (PA) is hypersensitive and hyperractive to histamine compared with that from a littermate control (C) in vitro. In this study, our aim was to determine whether the maximal velocity of shortening (Vmax) measured in strips of electrically stimulated SPA and CPA differed. Vmax (velocity at zero load) was obtained by analysis of force-velocity curves from these tissues using the equation (P + a) (V + b) = (Po + a)b, in which P is load, Po is maximum tetanic tension, V is shortening velocity, and a and b are asymptotic values in units of force and velocity. The Vmax values derived for SPA and CPA are 0.188 +/- 0.029 (SE) and 0.113 + 0.017 lo/s, respectively, lo being defined as that length at which Po is obtained. This result indicated that the Vmax value of SPA is significantly (P less than 0.05) different from that of CPA. The b values for SPA [0.034 +/- 0.003 lo/s] and for CPA [0.025 +/- 0.004 lo/s] were also significantly different. However, the force constants a and Po were unchanged in the SPA and CPA. SPA also had a greater isotonic shortening capacity than CPA. These findings indicate that mechanical properties of SPA are altered and lend an understanding of the hyperreactivity of these vessels in the sensitized model.

Scientific contributions of A. V. Hill: exercise physiology pioneer

2002 ◽  
Vol 93 (5) ◽  
pp. 1567-1582 ◽  
Author(s):  
David R. Bassett
Keyword(s):  
World War Ii ◽  
Heat Production ◽  
Time Course ◽  
Exercise Physiology ◽  
Frog Muscle ◽  
World War ◽  
Academic Assistance ◽  
Physiological Adaptations ◽  
Velocity Equation ◽  
Force Velocity

Beginning in 1910, A. V. Hill performed careful experiments on the time course of heat production in isolated frog muscle. His research paralleled that of the German biochemist Otto Meyerhof, who measured the changes in muscle glycogen and lactate during contractions and recovery. For their work in discovering the distinction between aerobic and anaerobic metabolism, Hill and Meyerhof were jointly awarded the 1922 Nobel Prize for Physiology or Medicine. Because of Hill's interest in athletics, he sought to apply the concepts discovered in isolated frog muscle to the exercising human. Hill and his colleagues made measurements of O2 consumption on themselves and other subjects running around an 85-m grass track. In the process of this work, they defined the terms “maximum O2 intake,” “O2requirement,” and “steady state of exercise.” Other contributions of Hill include his discoveries of heat production in nerve, the series elastic component, and the force-velocity equation in muscle. Around the time of World War II, Hill was a leading figure in the Academic Assistance Council, which helped Jewish scientists fleeing Nazi Germany to relocate in the West. He served as a member of the British Parliament from 1940 to 1945 and as a scientific advisor to India. Hill's vision and enthusiasm attracted many scientists to the field of exercise physiology, and he pointed the way toward many of the physiological adaptations that occur with physical training.

Force-velocity and force-power properties of single muscle fibers from elite master runners and sedentary men

1996 ◽  
Vol 271 (2) ◽  
pp. C676-C683 ◽  
Author(s):  
J. J. Widrick ◽  
S. W. Trappe ◽  
D. L. Costill ◽  
R. H. Fitts
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Power Output ◽  
Peak Power ◽  
Isometric Force ◽  
Peak Force ◽  
Peak Power Output ◽  
Type I ◽  
Shortening Velocity ◽  
Force Velocity

Gastrocnemius muscle fiber bundles were obtained by needle biopsy from five middle-aged sedentary men (SED group) and six age-matched endurance-trained master runners (RUN group). A single chemically permeabilized fiber segment was mounted between a force transducer and a position motor, subjected to a series of isotonic contractions at maximal Ca2+ activation (15 degrees C), and subsequently run on a 5% polyacrylamide gel to determine myosin heavy chain composition. The Hill equation was fit to the data obtained for each individual fiber (r2 > or = 0.98). For the SED group, fiber force-velocity parameters varied (P < 0.05) with fiber myosin heavy chain expression as follows: peak force, no differences: peak tension (force/fiber cross-sectional area), type IIx > type IIa > type I; maximal shortening velocity (Vmax, defined as y-intercept of force-velocity relationship), type IIx = type IIa > type I; a/Pzero (where a is a constant with dimensions of force and Pzero is peak isometric force), type IIx > type IIa > type I. Consequently, type IIx fibers produced twice as much peak power as type IIa fibers, whereas type IIa fibers produced about five times more peak power than type I fibers. RUN type I and IIa fibers were smaller in diameter and produced less peak force than SED type I and IIa fibers. The absolute peak power output of RUN type I and IIa fibers was 13 and 27% less, respectively, than peak power of similarly typed SED fibers. However, type I and IIa Vmax and a/Pzero were not different between the SED and RUN groups, and RUN type I and IIa power deficits disappeared after power was normalized for differences in fiber diameter. Thus the reduced absolute peak power output of the type I and IIa fibers from the master runners was a result of the smaller diameter of these fibers and a corresponding reduction in their peak isometric force production. This impairment in absolute peak power production at the single fiber level may be in part responsible for the reduced in vivo power output previously observed for endurance-trained athletes.

Power output from a flight muscle of the bumblebee Bombus terrestris. I. Some features of the dorso-ventral flight muscle

1997 ◽  
Vol 200 (8) ◽  
pp. 1215-1226 ◽  
Author(s):  
R Josephson ◽  
C Ellington
Keyword(s):  
Flight Muscle ◽  
Bombus Terrestris ◽  
Low Frequency ◽  
Muscle Strain ◽  
Optimal Length ◽  
Tetanic Force ◽  
Tethered Flight ◽  
Wing Stroke ◽  
Tetanic Tension

1. Isometric contractions from the asynchronous dorso-ventral flight muscle of the bumblebee Bombus terrestris were slow and rather weak. The twitch duration (onset to 50 % relaxation) was approximately 300 ms at 30 &deg;C and 170 ms at 40 &deg;C. The maximum tetanic tension was approximately 40 kN m-2; the ratio of twitch force to tetanic force was approximately 0.2. 2. The unstimulated muscle was quite resistant to stretch, with a low-frequency stiffness of 730 kN m-2 at muscle lengths close to that of the muscle in vivo. The length&shy;tension curve for active tetanic tension (that is the increase in tension above the passive level during stimulation) was very narrow, with a half-width equal to only 17 % of the optimal length. 3. The muscle strain during tethered flight was approximately 2 % peak-to-peak, occasionally reaching 3 %. Strain amplitude increased with wing stroke frequency. The thoracic vibration frequency of escape buzzing, during which the wings are not extended but are folded over the abdomen, was approximately twice that of tethered flight but the muscle strain was similar to that of flight.

Power output by an asynchronous flight muscle from a beetle

2000 ◽  
Vol 203 (17) ◽  
pp. 2667-2689 ◽  
Author(s):  
R.K. Josephson ◽  
J.G. Malamud ◽  
D.R. Stokes
Keyword(s):  
Power Output ◽  
Flight Muscle ◽  
Muscle Length ◽  
Mechanical Power ◽  
Effect Of Temperature ◽  
Muscle Temperature ◽  
Work Output ◽  
Stroke Frequency ◽  
Mechanical Power Output ◽  
Wing Stroke

The basalar muscle of the beetle Cotinus mutabilis is a large, fibrillar flight muscle composed of approximately 90 fibers. The paired basalars together make up approximately one-third of the mass of the power muscles of flight. Changes in twitch force with changing stimulus intensity indicated that a basalar muscle is innervated by at least five excitatory axons and at least one inhibitory axon. The muscle is an asynchronous muscle; during normal oscillatory operation there is not a 1:1 relationship between muscle action potentials and contractions. During tethered flight, the wing-stroke frequency was approximately 80 Hz, and the action potential frequency in individual motor units was approximately 20 Hz. As in other asynchronous muscles that have been examined, the basalar is characterized by high passive tension, low tetanic force and long twitch duration. Mechanical power output from the basalar muscle during imposed, sinusoidal strain was measured by the work-loop technique. Work output varied with strain amplitude, strain frequency, the muscle length upon which the strain was superimposed, muscle temperature and stimulation frequency. When other variables were at optimal values, the optimal strain for work per cycle was approximately 5%, the optimal frequency for work per cycle approximately 50 Hz and the optimal frequency for mechanical power output 60–80 Hz. Optimal strain decreased with increasing cycle frequency and increased with muscle temperature. The curve relating work output and strain was narrow. At frequencies approximating those of flight, the width of the work versus strain curve, measured at half-maximal work, was 5% of the resting muscle length. The optimal muscle length for work output was shorter than that at which twitch and tetanic tension were maximal. Optimal muscle length decreased with increasing strain. The curve relating work output and muscle length, like that for work versus strain, was narrow, with a half-width of approximately 3 % at the normal flight frequency. Increasing the frequency with which the muscle was stimulated increased power output up to a plateau, reached at approximately 100 Hz stimulation frequency (at 35 degrees C). The low lift generated by animals during tethered flight is consistent with the low frequency of muscle action potentials in motor units of the wing muscles. The optimal oscillatory frequency for work per cycle increased with muscle temperature over the temperature range tested (25–40 degrees C). When cycle frequency was held constant, the work per cycle rose to an optimum with increasing temperature and then declined. We propose that there is a temperature optimum for work output because increasing temperature increases the shortening velocity of the muscle, which increases the rate of positive work output during shortening, but also decreases the durations of the stretch activation and shortening deactivation that underlie positive work output, the effect of temperature on shortening velocity being dominant at lower temperatures and the effect of temperature on the time course of activation and deactivation being dominant at higher temperatures. The average wing-stroke frequency during free flight was 94 Hz, and the thoracic temperature was 35 degrees C. The mechanical power output at the measured values of wing-stroke frequency and thoracic temperature during flight, and at optimal muscle length and strain, averaged 127 W kg(−1)muscle, with a maximum value of 200 W kg(−1). The power output from this asynchronous flight muscle was approximately twice that measured with similar techniques from synchronous flight muscle of insects, supporting the hypothesis that asynchronous operation has been favored by evolution in flight systems of different insect groups because it allows greater power output at the high contraction frequencies of flight.

scholarly journals Power fatigue of the rat diaphragm muscle

2000 ◽  
Vol 89 (6) ◽  
pp. 2215-2219 ◽  
Author(s):  
Bill T. Ameredes ◽  
Wen-Zhi Zhan ◽  
Y. S. Prakash ◽  
Rene Vandenboom ◽  
Gary C. Sieck
Keyword(s):  
Diaphragm Muscle ◽  
Fiber Types ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Reduction In Force ◽  
Novel Technique ◽  
Velocity Relationship ◽  
Stimulus Train ◽  
Force Velocity

We hypothesized that decrements in maximum power output (W˙max) of the rat diaphragm (Dia) muscle with repetitive activation are due to a disproportionate reduction in force (force fatigue) compared with a slowing of shortening velocity (velocity fatigue). Segments of midcostal Dia muscle were mounted in vitro (26°C) and stimulated directly at 75 Hz in 400-ms-duration trains repeated each second (duty cycle = 0.4) for 120 s. A novel technique was used to monitor instantaneous reductions in maximum specific force (Po) andW˙max during fatigue. During each stimulus train, activation was isometric for the initial 360 ms during which Po was measured; the muscle was then allowed to shorten at a constant velocity (30% V max) for the final 40 ms, and W˙max was determined. Compared with initial values, after 120 s of repetitive activation, Po andW˙max decreased by 75 and 73%, respectively. Maximum shortening velocity was measured in two ways: by extrapolation of the force-velocity relationship ( V max) and using the slack test [maximum unloaded shortening velocity ( V o)]. After 120 s of repetitive activation, V max slowed by 44%, whereas V o slowed by 22%. Thus the decrease inW˙max with repetitive activation was dominated by force fatigue, with velocity fatigue playing a secondary role. On the basis of a greater slowing of V max vs. V o, we also conclude that force and power fatigue cannot be attributed simply to the total inactivation of the most fatigable fiber types.

Velocity-length-time relations in canine tracheal smooth muscle

1988 ◽  
Vol 64 (5) ◽  
pp. 2053-2057 ◽  
Author(s):  
C. Y. Seow ◽  
N. L. Stephens
Keyword(s):  
Smooth Muscle ◽  
Goodness Of Fit ◽  
Time Course ◽  
Muscle Length ◽  
Tracheal Smooth Muscle ◽  
Minimum Length ◽  
Shortening Velocity ◽  
Contracting Muscle ◽  
Parabolic Function ◽  
The Moment

Zero-load velocity (V0) as a function of the length of canine tracheal smooth muscle was obtained by applying zero-load clamps to isotonically contracting muscle under various loads. The load clamps were applied at a specific time after onset of contraction. The magnitude of the isotonic load therefore determines the length of the muscle at the moment of release or at the moment the unloaded shortening velocity was measured. A family of such V0-muscle length (L) curves was obtained at 1-s intervals in the time course of contraction. The V0-L curve was fitted by a parabolic function with satisfactory goodness of fit. The maximum shortening velocity at optimum muscle length varied with time, but the minimum length at which V0 diminished to zero was time independent.

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