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 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).

Isotonic contractile and fatigue properties of developing rat diaphragm muscle

1998 ◽  
Vol 84 (4) ◽  
pp. 1260-1268 ◽  
Author(s):  
Wen-Zhi Zhan ◽  
Jon F. Watchko ◽  
Y. S. Prakash ◽  
Gary C. Sieck
Keyword(s):  
Power Output ◽  
Supply And Demand ◽  
Maximum Power ◽  
Diaphragm Muscle ◽  
Fatigue Properties ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Endurance Time ◽  
Early Postnatal Development ◽  
Maximum Power Output

Postnatal transitions in myosin heavy chain (MHC) isoform expression were found to be associated with changes in both isometric and isotonic contractile properties of rat diaphragm muscle (Diam). Expression of MHCneo predominated in neonatal Diam fibers but was usually coexpressed with MHCslow or MHC2A isoforms. Expression of MHCneo disappeared by day 28. Expression of MHC2X and MHC2B emerged at day 14 and increased thereafter. Associated with these MHC transitions in the Diam, maximum isometric tetanic force (Po), maximum shortening velocity, and maximum power output progressively increased during early postnatal development. Maximum power output of the Diam occurred at ∼40% Po at days 0 and 7 and at ∼30% Po in older animals. Susceptibility to isometric and isotonic fatigue, defined as a decline in force and power output during repetitive activation, respectively, increased with maturation. Isotonic endurance time, defined as the time for maximum power output to decline to zero, progressively decreased with maturation. In contrast, isometric endurance time, defined as the time for force to decline to 30–40% Po, remained >300 s until after day 28. We speculate that with the postnatal transition to MHC2X and MHC2Bexpression energy requirements for contraction increase, especially during isotonic shortening, leading to a greater imbalance between energy supply and demand.

Salbutamol enhances isotonic contractile properties of rat diaphragm muscle

1998 ◽  
Vol 85 (2) ◽  
pp. 525-529 ◽  
Author(s):  
H. F. M. Van Der Heijden ◽  
W. Z. Zhan ◽  
Y. S. Prakash ◽  
P. N. R. Dekhuijzen ◽  
G. C. Sieck
Keyword(s):  
Power Output ◽  
Maximum Power ◽  
Contractile Properties ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Maximum Power Output ◽  
Isometric Twitch ◽  
Camp Levels

The effects of the β2-adrenoceptor agonist salbutamol (Slb) on isometric and isotonic contractile properties of the rat diaphragm muscle (Diamus) were examined. A loading dose of 25 μg/kg Slb was administered intracardially before Diamus excision to ensure adequate diffusion. Studies were then performed with 0.05 μM Slb in the in vitro tissue chamber. cAMP levels were determined by radioimmunoassay. Compared with controls (Ctl), cAMP levels were elevated after Slb treatment. In Slb-treated rats, isometric twitch and maximum tetanic force were increased by ∼40 and ∼20%, respectively. Maximum shortening velocity increased by ∼15% after Slb treatment, and maximum power output increased by ∼25%. During repeated isotonic activation, the rate of fatigue was faster in the Slb-treated Diamus, but both Slb-treated and Ctl Diamusfatigued to the same maximum power output. Still, endurance time during repetitive isotonic contractions was ∼10% shorter in the Slb-treated Diamus. These results are consistent with the hypothesis that β-adrenoceptor stimulation by Slb enhances Diamus contractility and that these effects of Slb are likely mediated, at least in part, by elevated cAMP.

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 TEMPERATURE, MUSCLE POWER OUTPUT AND LIMITATIONS ON BURST LOCOMOTOR PERFORMANCE OF THE LIZARD DIPSOSAURUS DORSALIS

1993 ◽  
Vol 174 (1) ◽  
pp. 185-197 ◽  
Author(s):  
S. J. Swoap ◽  
T. P. Johnson ◽  
R. K. Josephson ◽  
A. F. Bennett
Keyword(s):  
Power Output ◽  
Maximum Power ◽  
Stride Frequency ◽  
Cycle Frequency ◽  
Maximum Power Output ◽  
Mechanical Power Output ◽  
Cycling Frequency ◽  
Loop Technique ◽  
Fast Twitch

The mechanical power output of fast-twitch fibres from the iliofibularis of the lizard Dipsosaurus dorsalis was measured over a broad body temperature range using the oscillatory work-loop technique. The optimal cycling frequency, that frequency at which mechanical power output is maximal, increases with temperature from 3.3 Hz at 15°C to 20.1 Hz at 42°C. Maximum power output increases with temperature, from 20 W kg-1 at 15°C to 154 W kg-1 at 42°C, the largest power output yet measured using the work-loop technique. At low temperatures (15°C and 22°C), stride frequency during burst running is nearly identical to the optimal cycling frequency for in vitro power output, suggesting that maximum power output may limit hindlimb cycle frequency in vivo. However, at higher temperatures (35°C and 42°C), the optimal cycling frequency of the isolated muscle is significantly higher than the burst stride frequency, demonstrating that contractile events no longer limit hindlimb cycle frequency. At higher temperatures, it is thus unlikely that the fast-twitch fibres of this muscle in vivo attain their potential for maximum power output.

BODY SIZE, MUSCLE POWER OUTPUT AND LIMITATIONS ON BURST LOCOMOTOR PERFORMANCE IN THE LIZARD DIPSOSAURUS DORSALIS

1993 ◽  
Vol 174 (1) ◽  
pp. 199-213 ◽  
Author(s):  
T. P. Johnson ◽  
S. J. Swoap ◽  
A. F. Bennett ◽  
R. K. Josephson
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Power Output ◽  
Muscle Power ◽  
Muscle Length ◽  
Muscle Fibres ◽  
Dipsosaurus Dorsalis ◽  
Cycling Frequency ◽  
Length Changes

The power output of fast-glycolytic (FG) muscle fibres isolated from the iliofibularis (IF) muscle of desert iguanas (Dipsosaurus dorsalis) was measured at 35 sC using the oscillatory work-loop technique. To simulate cyclical muscle length changes during running, isolated fibre bundles were subjected to sinusoidal length changes and phasic stimulation during the strain cycle. At constant strain (12 %), the duration and timing (phase) of stimulation were adjusted to maximise power output. Using both hatchlings (4–8 g) and adults of varying sizes (15–70 g), the intraspecific allometries of IF length and contractile properties were described by regression analysis. The muscle length at which isometric force was maximum (L0, mm) increased geometrically with body mass (M, g) (L0=5.7M0.33). Maximum power output and the force produced during shortening showed no significant relationship to body size; work output per cycle (Wopt, J kg-1) under conditions required to maximise power did increase with body size (Wopt=3.7M0.24). Twitch duration (Td, ms), measured from the onset of force generation to 50 % relaxation, increased allometrically with body mass (Td=12.4M0.18). Limb cycling frequency during burst running (f, reported in the literature) and the frequency required to maximise power output in vitro (fopt) decreased with body size, both being proportional to body mass raised to the power 0.24. These findings suggest that limb cycling frequency may be limited by twitch contraction kinetics. However, despite corresponding proportionality to body size, limb cycling frequencies during burst running are about 20 % lower than the cycling frequencies required to maximise power output. Differences in the contractile performance of the IF in vitro and in vivo are discussed in relation to constraints imposed by gravitational forces and the design of muscular, nervous and skeletal systems.

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 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.

Are There Associations Between Submaximal and Maximal Aerobic Power and International Ski Federation World Cup Ranking in Elite Alpine Skiers?

2020 ◽  
pp. 1-6
Author(s):  
Wolfgang Schobersberger ◽  
Michael Mairhofer ◽  
Simon Haslinger ◽  
Arnold Koller ◽  
Christian Raschner ◽  
...  
Keyword(s):  
Body Mass Index ◽  
Oxygen Uptake ◽  
Body Mass ◽  
Power Output ◽  
Fixed Effects ◽  
Ventilatory Threshold ◽  
Maximum Power ◽  
World Cup ◽  
Maximum Power Output ◽  
Alpine Skiers

Purpose: To analyze the predictive value of parameters of submaximal and maximal cardiopulmonary exercise performance on International Ski Federation (Fédération Internationale de Ski) World Cup ranking (FIS ranking) in elite Austrian Alpine skiers. Methods: Over 7 World Cup seasons (2012–2018), exercise data (maximal oxygen uptake and maximum power output, lactate threshold 2, and ventilatory threshold 2, based on stepwise cycle spiroergometry) were analyzed to determine whether there was a correlation between world FIS ranking and exercise capacity of male and female elite Alpine skiers. Results: The data of 39 male skiers (age: 27.67 [4.20] y, body mass index: 26.03 [1.25] kg/m2) and 36 female skiers (age: 25.49 [3.18] y, body mass index: 22.97 [1.71] kg/m2) were included in this study. The maximum oxygen uptake and maximum power output ranged from 4.37 to 4.42 W/kg and 53.41 to 54.85 mL/kg/min in men and from 4.17 to 4.30 W/kg and 45.96 to 49.16 mL/kg/min in women, respectively, over the 7 seasons; the yearly mean FIS ranking ranged from 17 to 24 in men and 9 to 18 in women. In a fixed-effects model used for the subsequent panel regression analysis, no statistically significant effect on FIS ranking was found for the exercise parameters of interest. Conclusions: Neither maximal aerobic tests nor maximum power output significantly predicted competitive performance, as indexed by the FIS ranking. This reinforces the assumption that no single parameter determines competition performance in this complex sport. Therefore, identifying the optimum amount of endurance training remains a major challenge for athletes and coaches, as does identifying and improving the factors that determine performance.

Sign in / Sign up

Export Citation Format

Share Document