Effect of stimulus duty cycle and cycle frequency on power output during fatigue in rat diaphragm muscle doing oscillatory work

1993 ◽  
Vol 71 (12) ◽  
pp. 910-916 ◽  
Author(s):  
E. D. Stevens ◽  
D. A. Syme
Keyword(s):  
Duty Cycle ◽  
Muscle Power ◽  
Diaphragm Muscle ◽  
Cycle Duration ◽  
Rat Diaphragm ◽  
Cycle Frequency ◽  
Length Changes ◽  
The Difference ◽  
Work Done ◽  
Measuring Force

Isolated rat diaphragm muscle was stimulated repetitively to induce fatigue, and the work done during each contraction was measured. Work per cycle was calculated by measuring force as the activated muscle was subjected to sinusoidal length changes (from 97 to 103% of L0, where L0 is rest length). Work was calculated from the loop formed when force was plotted against length. Work done was positive when the muscle was shortening and was negative when it was lengthening; net work was the difference. Work output was varied by changing the stimulus duty cycle (4, 8, or 16% of the total cycle duration) and cycle frequency (1, 2, or 4 Hz). The rate and extent of the decrease in power was influenced much more by changes in cycle frequency than by changes in duty cycle. Duty cycle and cycle frequency combinations that resulted in greater power in the prefatigue trials were associated with a more rapid rate of fatigue. However, net positive power at the end of the 15-min fatigue period was greater under these same conditions (i.e., high duty cycle and high cycle frequency). Fatigue in working diaphragm muscle depends more on cycle frequency than on duty cycle.Key words: skeletal muscle, muscle power, respiratory muscle, muscle lengthening.

Effect of cycle frequency and excursion amplitude on work done by rat diaphragm muscle

1989 ◽  
Vol 67 (10) ◽  
pp. 1294-1299 ◽  
Author(s):  
D. A. Syme ◽  
E. D. Stevens
Keyword(s):  
Duty Cycle ◽  
Muscle Length ◽  
Diaphragm Muscle ◽  
Cycle Period ◽  
Rat Diaphragm ◽  
Mean Power ◽  
Cycle Frequency ◽  
Force Velocity ◽  
Isometric Twitch ◽  
Work Done

Strips of isolated rat diaphragm muscle were attached to a servomotor–transducer apparatus, and the muscle length was cycled in a sinusoidal fashion about the length at which maximum isometric twitch force was developed, Lo. The amplitude of the length displacement (excursion amplitude) and rate of cycling were varied between 3 and 13% Lo and 1–4 Hz respectively. The muscle was tetanically stimulated (100 Hz, supramaximal voltage, stimulus duration (duty cycle) 20% of the length cycle period) during the shortening stage of the imposed length cycle at the phase that yielded maximum net positive work. The force and displacement of the muscle were recorded. Work per cycle was calculated from the area of the loop formed by plotting force against length for one full stretch–shorten cycle. Work per cycle decreased, but power increased, as cycle frequency was increased from 1 to 4 Hz. Maximum work done per cycle was about 12.8 J/kg at a cycle frequency of 1 Hz. Maximum mean power developed was about 27 W/kg and occurred at a cycle frequency of 4 Hz. Work and power were maximum at an excursion amplitude of 13% of Lo (i.e., Lo ± 6.5%). Measured work and power output are considerably less than values estimated from length–tension and force-velocity curves.Key words: rat, diaphragm, work, power, duty cycle.

Effect of stimulus train duration and cycle frequency on the capacity to do work in the pectoral fin muscle of the pumpkinseed sunfish, Lepomis gibbosus

1993 ◽  
Vol 71 (11) ◽  
pp. 2185-2189 ◽  
Author(s):  
Eric A. Luiker ◽  
E. Don Stevens
Keyword(s):  
Duty Cycle ◽  
Length Change ◽  
Lepomis Gibbosus ◽  
Pectoral Fin ◽  
Cycle Frequency ◽  
Pumpkinseed Sunfish ◽  
Train Duration ◽  
Stimulus Train ◽  
Length Changes ◽  
Time Required

The goal of our experiment was to elucidate the effect of stimulus duty cycle (the percentage of the cycle that the muscle was stimulated), phase (the relative timing of the imposed sinusoidal length change and stimulation), and muscle cycle frequency (the speed at which the muscle was cycled) on work and power in the pectoral fin muscle of a labriform swimmer, the pumpkinseed sunfish, Lepomis gibbosus. Stimulus train duration was varied from a twitch to a 40% duty cycle; cycle frequency was varied from 1 to 8 Hz. Work was calculated as the area of work loops produced by muscle contractions while the muscle was undergoing sinusoidal length changes. Maximum net work per cycle (6.2 J/kg) was produced at 1 Hz cycle frequency and a 32% duty cycle. Maximum power (26.7 W/kg) was produced at 5 Hz cycle frequency and a 16% duty cycle. As cycle frequency increased, the duty cycle and the stimulus train duration that produced maximum work decreased. The relatively long relaxation time compared with the length of time required to complete the whole cycle precluded the muscle from doing net positive work at high cycle frequencies.

Effect of phase of stimulation on acute damage caused by eccentric contractions in mouse soleus muscle

1996 ◽  
Vol 80 (6) ◽  
pp. 1958-1962 ◽  
Author(s):  
E. D. Stevens
Keyword(s):  
Muscle Damage ◽  
Length Change ◽  
Eccentric Contractions ◽  
Single Trial ◽  
Loop Method ◽  
Significant Damage ◽  
Length Changes ◽  
The Difference ◽  
Work Done ◽  
Work Loop

Eccentric contractions (activation during muscle lengthening) can cause muscle damage. The effect of phase of stimulation on the extent of muscle damage was studied by using the work-loop method. For the work-loop method, the muscle was subjected to sinusoidal length changes at 2 Hz. The muscle was activated at different times during the imposed length-change cycle; this time is called the phase of stimulation. Work was calculated from the loop formed when force was plotted against length. Work done was positive when the muscle was shortening and was negative when the muscle was lengthening; net work was the difference. One complete length-change cycle was 100 (i.e., given as a percentage of the cycle); shortening occurred from 25 to 75. The muscle did the most net work when stimulated at phase 20, that is, when activation started just before shortening. Damage was defined as a decrease in work. Significant damage occurred after a single trial of three consecutive eccentric contractions; the muscle did less positive and less net work because of the damage. Maximal damage occurred at phases 90 and 0, the center of the lengthening part of the length-change cycle (work decreased 10%). Negligible damage occurred at phases 20-40. Negative work (work required to lengthen the muscle) also decreased because of the damage. Eccentric contractions caused much more damage than concentric contractions during oscillatory work.

scholarly journals Modelling Muscle Power Output in a Swimming Fish

1990 ◽  
Vol 148 (1) ◽  
pp. 395-402 ◽  
Author(s):  
JOHN D. ALTRINGHAM ◽  
IAN A. JOHNSTON
Keyword(s):  
Power Output ◽  
Muscle Power ◽  
Fish Swimming ◽  
Active Muscle ◽  
Cycle Frequency ◽  
Fibre Bundles ◽  
Length Changes ◽  
Myoxocephalus Scorpius ◽  
Myotomal Muscle ◽  
Muscle Power Output

Intact, electrically excitable fibre bundles were isolated from the fast and slow myotomal muscle of the bullrout (Myoxocephalus scorpius L.). Power output was measured under conditions simulating their activity in a fish swimming at different speeds. Preparations were subjected to sinusoidal length changes of ±5% of resting length, and stimulated briefly during each cycle. The number and timing of stimuli were adjusted at each cycle frequency to maximise power output. Maximum power was produced at 5–7 Hz for fast fibres (25–35 W kg−1) and 2 Hz for slow fibres (5–8 Wkg−1). Under these conditions, pre-stretch of active muscle provides an important mechanism for storing potential energy for release during the shortening part of the cycle.

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.

scholarly journals Modeling red muscle power output during steady and unsteady swimming in largemouth bass

1994 ◽  
Vol 267 (2) ◽  
pp. R481-R488 ◽  
Author(s):  
T. P. Johnson ◽  
D. A. Syme ◽  
B. C. Jayne ◽  
G. V. Lauder ◽  
A. F. Bennett
Keyword(s):  
Power Output ◽  
Largemouth Bass ◽  
Muscle Power ◽  
Micropterus Salmoides ◽  
Cycle Frequency ◽  
Red Muscle ◽  
Slow Twitch ◽  
Work Done

We recorded electromyograms of slow-twitch (red) muscle fibers and videotaped swimming in the largemouth bass (Micropterus salmoides) during cruise, burst-and-glide, and C-start maneuvers. By use of in vivo patterns of stimulation and estimates of strain, in vitro power output was measured at 20 degrees C with the oscillatory work loop technique on slow-twitch fiber bundles from the midbody area near the soft dorsal fin. Power output increased slightly with cycle frequency to a plateau of approximately 10 W/kg at 3-5 Hz, encompassing the normal range of tail-beat frequencies for steady swimming (approximately 2-4 Hz). Power output declined at cycle frequencies simulating unsteady swimming (burst-and-glide, 10 Hz; C-start, 15 Hz). However, activating the muscle at 10 Hz did significantly increase the net work done compared with the work produced by the inactive muscle (work done by the viscous and elastic components). Thus this study provides further insight into the apparently paradoxical observation that red muscle can contribute little or no power and yet continues to show some recruitment during unsteady swimming. Comparison with published values of power requirements from oxygen consumption measurements indicates a limit to steady swimming speed imposed by the maximum power available from red muscle.

scholarly journals Mechanical efficiency and efficiency of storage and release of series elastic energy in skeletal muscle during stretch-shorten cycles.

1996 ◽  
Vol 199 (9) ◽  
pp. 1983-1997
Author(s):  
G J Ettema
Keyword(s):  
Elastic Energy ◽  
Muscle Power ◽  
Mechanical Energy ◽  
Mechanical Efficiency ◽  
Contractile Element ◽  
Cycle Frequency ◽  
External Work ◽  
Work Done ◽  
Series Elastic

The mechanical energy exchanges between components of a muscle-tendon complex, i.e. the contractile element (CE) and the series elastic element (SEE), and the environment during stretch-shorten cycles were examined. The efficiency of the storage and release of series elastic energy (SEE efficiency) and the overall mechanical efficiency of the rat gastrocnemius muscle (N = 5) were determined for a range of stretch-shorten contractions. SEE efficiency was defined as elastic energy released to the environment divided by external work done upon the muscle-tendon complex plus internal work exchange from the CE to the SEE. Mechanical efficiency is external work done by the muscle-tendon complex divided by the external work done upon the muscle-tendon complex plus work done by the CE. All stretch-shorten cycles were performed with a movement amplitude of 3mm (6.7% strain). Cycle frequency, duty factor and the onset of stimulation were altered for the different cycles. SEE efficiency varied from 0.02 to 0.85, mechanical efficiency from 0.43 t 0.92. SEE efficiency depended on the timing of stimulation and net muscle power in different ways. Mechanical efficiency was much more closely correlated with net power. The timing of muscle relaxation was crucial for the effective release of elastic energy. Simulated in vivo contractions indicated that during rat locomotion the gastrocnemius may have a role other than that of effectively storing elastic energy and generating work. Computer simulations showed that the amount of series elastic compliance can affect the internal energetics of a muscle contraction strongly without changing the muscle force generation dramatically.

scholarly journals Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle

1997 ◽  
Vol 83 (4) ◽  
pp. 1062-1067 ◽  
Author(s):  
Roland H. H. Van Balkom ◽  
Wen-Zhi Zhan ◽  
Y. S. Prakash ◽  
P. N. Richard Dekhuijzen ◽  
Gary C. Sieck
Keyword(s):  
Isometric Force ◽  
Contractile Properties ◽  
Diaphragm Muscle ◽  
Peak Power Output ◽  
Rat Diaphragm ◽  
Fiber Morphology ◽  
Shortening Velocity ◽  
Maximum Isometric Force ◽  
Induced Changes ◽  
Isotonic Contractions

Van Balkom, Roland H. H., Wen-Zhi Zhan, Y. S. Prakash, P. N. Richard Dekhuijzen, and Gary C. Sieck. Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle. J. Appl. Physiol. 83(4): 1062–1067, 1997.—The effects of corticosteroids (CS) on diaphragm muscle (Diam) fiber morphology and contractile properties were evaluated in three groups of rats: controls (Ctl), surgical sham and weight-matched controls (Sham), and CS-treated (6 mg ⋅ kg−1 ⋅ day−1prednisolone at 2.5 ml/h for 3 wk). In the CS-treated Diam, there was a selective atrophy of type IIx and IIb fibers, compared with a generalized atrophy of all fibers in the Sham group. Maximum isometric force was reduced by 20% in the CS group compared with both Ctl and Sham. Maximum shortening velocity in the CS Diamwas slowed by ∼20% compared with Ctl and Sham. Peak power output of the CS Diam was only 60% of Ctl and 70% of Sham. Endurance to repeated isotonic contractions improved in the CS-treated Diam compared with Ctl. We conclude that the atrophy of type IIx and IIb fibers in the Diam can only partially account for the CS-induced changes in isotonic contractile properties. Other factors such as reduced myofibrillar density or altered cross-bridge cycling kinetics are also likely to contribute to the effects of CS treatment.

Interstitial space and collagen alterations of the developing rat diaphragm

1993 ◽  
Vol 74 (5) ◽  
pp. 2450-2455 ◽  
Author(s):  
L. E. Gosselin ◽  
D. A. Martinez ◽  
A. C. Vailas ◽  
G. C. Sieck
Keyword(s):  
Postnatal Growth ◽  
Interstitial Space ◽  
Collagen Content ◽  
Diaphragm Muscle ◽  
Adult Males ◽  
Rat Diaphragm ◽  
Collagen Concentration ◽  
Cross Sectional ◽  
Hydroxyproline Concentration ◽  
Total Muscle

The effect of growth on the relative interstitial space [%total cross-sectional area (CSA)] and collagen content of the rat diaphragm muscle was examined at postnatal ages of 0, 7, 14, and 21 days as well as in adult males. The proportion of interstitial space relative to total muscle CSA was determined by computerized image analysis of lectin-stained cross sections of diaphragm muscle. To assess collagen content and extent of collagen maturation (i.e., cross-linking), high-pressure liquid chromatography analysis was used to measure hydroxyproline concentration and the nonreducible collagen cross-link hydroxylysylpyridinoline (HP), respectively. At birth, interstitial space accounted for approximately 47% of total diaphragm muscle CSA. During postnatal growth, the relative contribution of interstitial space decreased such that by adulthood the interstitial space accounted for approximately 18% of total muscle CSA. The change in relative interstitial space occurred without a concomitant change in hydroxyproline concentration. However, the concentration of HP markedly increased with age such that the adult diaphragm contained approximately 17 times more HP than at birth. These results indicate that during development the relative CSA occupied by interstitial space decreases as muscle fiber size increases. However, the reduction in relative interstitial space is not associated with a change in collagen concentration. Thus collagen density in the interstitial space may increase with age. It is possible that the observed changes in relative interstitial space and collagen influence the passive length-force properties of the diaphragm.

Sign in / Sign up

Export Citation Format

Share Document