POWER OUTPUT OF FISH MUSCLE FIBRES PERFORMING OSCILLATORY WORK: EFFECTS OF ACUTE AND SEASONAL TEMPERATURE CHANGE

1991 ◽  
Vol 157 (1) ◽  
pp. 409-423 ◽  
Author(s):  
TIMOTHY P. JOHNSON ◽  
IAN A. JOHNSTON
Keyword(s):  
Strain Amplitude ◽  
Power Output ◽  
Muscle Length ◽  
Fast Muscle ◽  
Muscle Fibres ◽  
Work Output ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Resting Muscle ◽  
Positive Work

Fast muscle fibres were isolated from the abdominal myotomes of the shorthorned sculpin Myoxocephalus scorpius L. Sinusoidal length changes were imposed about resting muscle length and fibres were stimulated at a selected phase during the strain cycle. The work output per cycle was calculated from the area of the resulting force-position loops. The strain amplitude required for maximum work per cycle had a distinct optimum at ±5 % of resting length, which was independent of temperature. Maximum positive work loops were obtained by retarding the stimulus relative to the start of the length-change cycle by 30° (full cycle=360°). The maximum negative work output was obtained with a 210° stimulus phase shift. At intermediate stimulus phase shifts, work loops became complex with both positive (anticlockwise) and negative (clockwise) components. The number and timing of stimuli were adjusted, at constant strain amplitude (±5% of resting muscle length), to optimize net positive work output over a range of cycle frequencies. The cycle frequency required for maximum power output (work per cycle times cycle frequency) increased from around 5–7 Hz at 4°C to 9–13 Hz at 15°C. The maximum tension generated per cycle at 15°C was around two times higher at all cycle frequencies in summer-relative to winter-acclimatized fish. Fast muscle fibres from summer fish produced consistently higher tensions at 4°C, but the differences were only significant at 15 Hz. Acclimatization also modified the relationship between peak length and peak force at 4°C and 15°C. The maximum power output of muscle fibres showed little seasonal variation at 4°C and was in the range 20–25 W kg−1. In contrast, at 15°C, maximum muscle power output increased from 9 W kg−1 in the winter- to 30 W kg−1 in the summeracclimatized fish

scholarly journals Scaling of Power Output in Fast Muscle Fibres of the Atlantic Cod During Cyclical Contractions

1992 ◽  
Vol 170 (1) ◽  
pp. 143-154 ◽  
Author(s):  
M. ELIZABETH ANDERSON ◽  
IAN A. JOHNSTON
Keyword(s):  
Steady State ◽  
Power Output ◽  
Standard Length ◽  
Atlantic Cod ◽  
Maximum Power ◽  
Fast Muscle ◽  
Muscle Fibres ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Length Changes

Fast muscle fibres were isolated from abdominal myotomes of Atlantic cod (Gadus morhua L.) ranging in size from 10 to 63 cm standard length (Ls). Muscle fibres were subjected to sinusoidal length changes about their resting length (Lf) and stimulated at a selected phase of the strain cycle. The work performed in each oscillatory cycle was calculated from plots of force against muscle length, the area of the resulting loop being net work. Strain and the number and timing of stimuli were adjusted to maximise positive work per cycle over a range of cycle frequencies at 8°C. Force, and hence power output, declined with increasing cycles of oscillation until reaching a steady state around the ninth cycle. The strain required for maximum power output (Wmax) was ±7-11% of Lf in fish shorter than 18 cm standard length, but decreased to ±5 % of Lf in larger fish. The cycle frequency required for Wmax also declined with increasing fish length, scaling to Ls−0.51 under steady-state conditions (cycles 9–12). At the optimum cycle frequency and strain the maximum contraction velocity scaled to Ls−0.79. The maximum stress (Pmax) produced within a cycle was highest in the second cycle, ranging from 51.3 kPa in 10 cm fish to 81.8 kPa in 60 cm fish (Pmax=28.2Ls0.25). Under steady-state conditions the maximum power output per kilogram wet muscle mass was found to range from 27.5 W in a 10 cm Ls cod to 16.4 W in a 60 cm Ls cod, scaling with Ls−0.29 and body mass (Mb)−0.10 Note: To whom reprint requests should be sent

scholarly journals Scaling Effects on Muscle Function: Power Output of Isolated Fish Muscle Fibres Performing Oscillatory Work

1990 ◽  
Vol 151 (1) ◽  
pp. 453-467 ◽  
Author(s):  
JOHN D. ALTRINGHAM ◽  
IAN A. JOHNSTON
Keyword(s):  
Power Output ◽  
Fibre Length ◽  
Fish Muscle ◽  
Maximum Power ◽  
Muscle Fibres ◽  
Scaling Effects ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Wide Range ◽  
Length Changes

Bundles of 3–10 live fast fibres were isolated from the abdominal myotomes of cod (Gadus morhua L.) 13–67 cm in length. The preparations performed work under conditions simulating their activity during swimming: sinusoidal length changes were imposed about in situ fibre length, and the fibres were stimulated at a selected phase in each cycle. Strain amplitude, and the number and timing of stimuli were chosen to give maximum power output over a wide range of cycle/tailbeat frequencies. For each preparation power output was maximal at a particular frequency, although the peaks were rather broad. As the size of the fish increased the cycle frequency for maximum power output (fopt) decreased, from 12.5 Hz (13 cm fish) to 5 Hz (67 cm fish) (fopt= 1.67 L−0.52, where L is body length).

scholarly journals Power output and the frequency of oscillatory work in mammalian diaphragm muscle: the effects of animal size

1991 ◽  
Vol 157 (1) ◽  
pp. 381-389 ◽  
Author(s):  
J. D. Altringham ◽  
I. S. Young
Keyword(s):  
Body Mass ◽  
Power Output ◽  
Maximum Power ◽  
Diaphragm Muscle ◽  
Muscle Fibres ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Oscillatory Power ◽  
Length Changes ◽  
Animal Size

Bundles of muscle fibres were isolated from the diaphragm of mouse, rat and rabbit. Mean oscillatory power output was determined during phasic stimulation and imposed sinusoidal length changes. Maximum power output was measured over a range of cycle frequencies. The cycle frequency for maximum power output (fopt) decreased with increasing body mass and was described by the equation, fopt = 4.42M-0.16, where M is body mass. A very similar relationship has been reported between body mass and the frequency of the trot-gallop transition in terrestrial, quadrupedal mammals [Heglund et al. (1974), Science 186, 1112–1113), and the significance of this similarity is discussed.

The effects of length trajectory on the mechanical power output of mouse skeletal muscles.

1997 ◽  
Vol 200 (24) ◽  
pp. 3119-3131 ◽  
Author(s):  
G N Askew ◽  
R L Marsh
Keyword(s):  
Strain Amplitude ◽  
Power Output ◽  
Maximum Power ◽  
Mechanical Power ◽  
Shortening Velocity ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Mechanical Power Output ◽  
Evolutionary Context

The effects of length trajectory on the mechanical power output of mouse soleus and extensor digitorum longus (EDL) muscles were investigated using the work loop technique in vitro at 37 degrees C. Muscles were subjected to sinusoidal and sawtooth cycles of lengthening and shortening; for the sawtooth cycles, the proportion of the cycle spent shortening was varied. For each cycle frequency examined, the timing and duration of stimulation and the strain amplitude were optimized to yield the maximum power output. During sawtooth length trajectories, power increased as the proportion of the cycle spent shortening increased. The increase in power was attributable to more complete activation of the muscle due to the longer stimulation duration, to a more rapid rise in force resulting from increased stretch velocity and to an increase in the optimal strain amplitude. The power produced during symmetrical sawtooth cycles was 5-10 % higher than during sinusoidal work loops. Maximum power outputs of 92 W kg-1 (soleus) and 247 W kg-1 (EDL) were obtained by manipulating the length trajectory. For each muscle, this was approximately 70 % of the maximum power output estimated from the isotonic force-velocity relationship. We have found a number of examples suggesting that animals exploit prolonging the shortening phase during activities requiring a high power output, such as flying, jet-propulsion swimming and vocalization. In an evolutionary context, increasing the relative shortening duration provides an alternative to increasing the maximum shortening velocity (Vmax) as a way to increase power output.

scholarly journals Efficiency of fast- and slow-twitch muscles of the mouse performing cyclic contractions.

1994 ◽  
Vol 193 (1) ◽  
pp. 65-78 ◽  
Author(s):  
C J Barclay
Keyword(s):  
Heat Production ◽  
Power Output ◽  
Muscle Length ◽  
Mechanical Efficiency ◽  
Maximum Efficiency ◽  
Work Output ◽  
Cycle Frequency ◽  
Length Changes ◽  
Slow Twitch ◽  
Initial Heat

The mechanical efficiency of mouse fast- and slow-twitch muscle was determined during contractions involving sinusoidal length changes. Measurements were made of muscle length, force production and initial heat output from bundles of muscle fibres in vitro at 31 degrees C. Power output was calculated as the product of the net work output per sinusoidal length cycle and the cycle frequency. The initial mechanical efficiency was defined as power output/(rate of initial heat production+power output). Both power output and rate of initial heat production were averaged over a full cycle of length change. The amplitude of length changes was +/- 5% of muscle length. Stimulus phase and duration were adjusted to maximise net work output at each cycle frequency used. The maximum initial mechanical efficiency of slow-twitch soleus muscle was 0.52 +/- 0.01 (mean +/- 1 S.E.M. N = 4) and occurred at a cycle frequency of 3 Hz. Efficiency was not significantly different from this at cycle frequencies of 1.5-4 Hz, but was significantly lower at cycle frequencies of 0.5 and 1 Hz. The maximum efficiency of fast-twitch extensor digitorum longus muscle was 0.34 +/- 0.03 (N = 4) and was relatively constant (0.32-0.34) over a broad range of frequencies (4-12 Hz). A comparison of these results with those from previous studies of the mechanical efficiency of mammalian muscles indicates that efficiency depends markedly on contraction protocol.

scholarly journals The Mechanical Power Output of a Crab Respiratory Muscle

1988 ◽  
Vol 140 (1) ◽  
pp. 287-299 ◽  
Author(s):  
DARRELL R. STOKES ◽  
ROBERT K. JOSEPHSON
Keyword(s):  
Power Output ◽  
Muscle Power ◽  
Beat Frequency ◽  
Muscle Length ◽  
Metabolic Energy ◽  
Mechanical Power ◽  
Work Output ◽  
Hydraulic Power ◽  
Cycle Frequency ◽  
Mechanical Power Output

The mechanical power output was measured from scaphognathite (SG = gill bailer) muscle L2B of the crab Carcinus maenas (L.). The work was determined from the area of the loop formed by plotting muscle length against force when the muscle was subjected to sinusoidal length change (strain) and phasic stimulation in the length cycle. The stimulation pattern (10 stimuli per burst, burst length = 20% of cycle length) mimicked that which has been recorded from muscle L2B in intact animals. Work output was measured at cycle frequencies ranging from 0.5 to 5 Hz. The work output at optimum strain and stimulus phase increased with increasing cycle frequency to a maximum at 2–3 Hz and declined thereafter. The maximum work per cycle was 2.7 J kg−1 (15 °C). The power output reached a maximum (8.8 W kg−1) at 4 Hz. Both optimum strain and optimum stimulus phase were relatively constant over the range of burst frequencies examined. Based on the fraction of the total SG musculature represented by muscle L2B (18%) and literature values for the oxygen consumption associated with ventilation in C. maenas and for the hydraulic power output from an SG, we estimate that at a beat frequency of 2 Hz the SG muscle is about 10% efficient in converting metabolic energy to muscle power, and about 19% efficient in converting muscle power to hydraulic power.

scholarly journals The effect of cycle frequency on the power output of rat papillary muscles in vitro.

1995 ◽  
Vol 198 (4) ◽  
pp. 1035-1043 ◽  
Author(s):  
J Layland ◽  
I S Young ◽  
J D Altringham
Keyword(s):  
Phase Shift ◽  
Strain Amplitude ◽  
Power Output ◽  
Maximum Power ◽  
Papillary Muscles ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Work Production

Papillary muscles were isolated from the right ventricles of rats and the length for maximum active force generation (Lmax) was determined isometrically. The work loop technique was used to derive the length for maximum work production (Lopt) at the cycle frequency, strain amplitude and stimulation phase shift found to be optimal for power output. Lopt was typically 7% shorter than Lmax and within the physiological length range (87.5% Lmax to Lmax). Net work and power output were measured during sinusoidal strain cycles around Lopt, over the cycle frequency range 1-9 Hz, strain amplitude and phase shift being optimised for work and power at each frequency. Experiments were performed at 37 degrees C. Distinct optima were found in both the work-frequency and the power-frequency relationships. The optimum cycle frequency for net work production was lower than the frequency for maximum power output. The mean maximum power output at 37 degrees C was 8.62 +/- 0.50 W kg-1 (mean +/- S.E.M., N = 9) and was achieved at a cycle frequency of approximately 6 Hz, close to the estimated resting heart rate of 5.8 Hz for the rats used (mean mass 223 +/- 25 g). The cycle frequency, strain amplitude and stimulation phase shift found to be optimal for power output produced an in vitro contraction closely simulating the basal in vivo contraction.

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 RECRUITMENT PATTERNS AND CONTRACTILE PROPERTIES OF FAST MUSCLE FIBRES ISOLATED FROM ROSTRAL AND CAUDAL MYOTOMES OF THE SHORT-HORNED SCULPIN

1993 ◽  
Vol 185 (1) ◽  
pp. 251-265 ◽  
Author(s):  
I. A. Johnston ◽  
C. E. Franklin ◽  
T. P. Johnson
Keyword(s):  
Power Output ◽  
High Speed ◽  
Prey Capture ◽  
The Body ◽  
Contractile Properties ◽  
Fast Muscle ◽  
Muscle Fibres ◽  
Length Changes ◽  
Tail Beat ◽  
Positive Work

Muscle action during swimming and the contractile properties of isolated muscle fibres were studied in the short-horned sculpin Myoxocephalus scorpius at 5°C. Semi-steady swimming, startle responses and prey-capture events were filmed with a high-speed video at 200 frames s-1, using fish 22–26 cm in total length (L). Electromyographical (EMG) recordings, synchronised with the video, were made from fast muscle in rostral and caudal myotomes at points 0.40L and 0.80L along the body. Fast muscle fibres were first recruited at tail-beat frequencies of 3.7-4.2 Hz, corresponding to a swimming speed of 1.7 L s-1. Electrical activity in the muscles occurred during 16–38 % of each tail- beat cycle regardless of frequency. Muscle fibres were activated during the lengthening phase of the cycle. In caudal myotomes, the onset of the muscle activity occurred at a phase of 75–105° at 3.7 Hz, decreasing to approximately 50° at frequencies greater than 4.5 Hz (0° phase was defined as the point at which muscle fibres passed through their resting lengths in the stretch phase of the cycle; a full cycle is 360°). Prey capture was a stereotyped behaviour consisting of a preparatory movement, a powerstroke at 7–9 Hz and a glide of variable duration. The delay between the activation of muscle fibres in rostral and caudal myotomes during prey capture and startle responses was approximately 10 ms. Fast muscle fibres isolated from rostral and caudal myotomes were found to have similar isometric contractile properties. Maximum tetanic stress was 220 kN m-2, and half-times for force development and relaxation were approximately 50 ms and 135 ms respectively. Power output was measured by the ‘work loop’ technique in muscle fibres subjected to sinusoidal length changes at the range of frequencies found during swimming. Under optimal conditions of strain and stimulation, muscle fibres from rostral and caudal myotomes produced similar levels of work (3.5 J kg-1) and generated their maximum power output of 25–30 W kg-1 at the tail-beat frequencies used in swimming (4–8 Hz). Progressively delaying the onset of stimulation relative to the start of the strain cycle resulted in an initial modest increase, followed by a decline, in the work per cycle. Maximum positive work and net negative work were done at stimulus phase values of 20–50° and 120–140° respectively. The EMG and swimming studies suggest that fast muscle fibres in both rostral and caudal myotomes do net positive work under most conditions.

EFFICIENCY OF ENERGY CONVERSION DURING SINUSOIDAL MOVEMENT OF WHITE MUSCLE FIBRES FROM THE DOGFISH SCYLIORHINUS CANICULA

1993 ◽  
Vol 183 (1) ◽  
pp. 137-147 ◽  
Author(s):  
N. A. Curtin ◽  
R. C. Woledge
Keyword(s):  
Power Output ◽  
High Efficiency ◽  
Fibre Length ◽  
Dry Mass ◽  
Energy Output ◽  
Maximum Efficiency ◽  
Muscle Fibres ◽  
Work Output ◽  
Sinusoidal Movement ◽  
Myotomal Muscle

Net work output and heat production of white myotomal muscle fibres from the dogfish were measured during complete cycles of sinusoidal movement at 12°C. The peak-to-peak movement was about 9 % of the muscle fibre length; three stimuli at 32 ms intervals were given in each mechanical cycle. The frequency of movement and the timing of the stimulation were varied for each preparation to find the optimal conditions for power output and those optimal for efficiency (the ratio of net work output to total energy output as heat+work). To achieve either maximum power or maximum efficiency, the tetanus must start while the muscle fibres are being stretched, before the beginning of the shortening part of the mechanical cycle. The highest power output, averaged over one cycle, was 0.23+/−0.014 W g-1 dry mass (+/−s.e.m., N=9, 46.9+/−2.8 mW g-1 wet mass) and was produced during movement at 3.5 Hz. The highest efficiency, 0.41+/−0.02 (+/−s.e.m., N=13), occurred during movements at 2.0-2.5 Hz. This value is higher than the efficiency previously measured during isovelocity shortening of these fibres. The implications of the high efficiency for crossbridge models of muscle contraction are discussed.

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