The mechanical efficiency of frog’s muscle

Hill, A. V.

doi:10.1098/rspb.1939.0033

Cited by 68 publications

(14 citation statements)

References 2 publications

(4 reference statements)

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“…WO7ODS different speeds depends on many factors, but forces up to 1-8 Po have been reported (Katz, 1939;Abbott, Aubert & Hill, 1951). Hill (1939) showed that maximum efficiency of muscle shortening occurs at 0-2 Vmax* We found subjects cycled with maximum efficiency at speeds of rev/mill, a conclusion which can also be drawn from the work of Asmussen (1952) and Banister & Jackson (1967) (Fig. 2).…”

Section: Discussionsupporting

confidence: 74%

Integrated electromyogram and oxygen uptake during positive and negative work.

Bigland-Ritchie¹,

Woods²

1976

The Journal of Physiology

260

157

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SUMMARY1. Integrated electromyogram (e.m.g.) from the vastus lateralis muscles, and steady-state rates of oxygen uptake, were measured simultaneously during the performance of set rates of positive (concentric) and negative (eccentric) work at 50 rev/min on a motorized bicycle ergometer.2. Similar experiments were also carried out at other pedalling rates and using other leg muscles.3. The relationships between each of the variables (integrated e.m.g., oxygen consumption) and mean torque on pedals were found to be lineal (r > 0-98) with a remarkable degree of reproducibility in surface e.m.g. for each subject over several months.4. The ratio of the e.m.g. slopes at 50 rev/min (positive/negative) was 1-96 + 0-12 while the same ratio for the oxygen uptake slopes was 6-34 + 0-82. The discrepancy between the ratios suggests that not only is less muscle fibre activity required to maintain the same exerted force during negative work exercise, but there is also a substantial reduction in the oxygen uptake when the fibres are stretched. This was observed for all speeds of pedalling.

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Section: Discussionsupporting

confidence: 74%

Integrated electromyogram and oxygen uptake during positive and negative work.

Bigland-Ritchie¹,

Woods²

1976

The Journal of Physiology

260

157

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“…9A). Mechanical efficiency for ramp shortening had a maximum value of 0-36 at about 1/5 VI; the peak of the efficiency preceded the peak of the power (about 1/3 VO), as already described for whole frog sartorius muscle by Hill (1938Hill ( , 1939. For staircase shortening the efficiency was lower than during ramp shortening.…”

Section: Consequently While For Velocities Lower Than 0 4 Lo S-'mentioning

confidence: 89%

Comparison of energy output during ramp and staircase shortening in frog muscle fibres.

Linari

Woledge

1995

The Journal of Physiology

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1. We compared the rates of work and heat production during ramp shortening with those during staircase shortening (sequence of step releases of the same amplitude, separated by regular time intervals). Ramp or staircase shortening was applied to isolated muscle fibres (sarcomere length, 2-2 ,sm; temperature, 1 00) at the plateau of an isometric tetanus. The total amount of shortening was no greater than 6 % of the fibre length. 2. During ramp shortening the power output showed a maximum at about 0-8 fibre lengths per second (Lo C1), which corresponds to 1/3 the maximum shortening velocity (VO). For the same average shortening velocity during staircase shortening (step size, -0 5% Lo) the power output was 40-60% lower. The rate of heat production for the same average shortening velocity was -45% higher during staircase shortening than during ramp shortening. 3. The relation between rate of total energy output and shortening velocity was well described by a second order regression line in the range of velocities used (0 1-2 3 Lo s-1). For any shortening velocity the rate of total energy output (power plus heat rate) was not statistically different for staircase (step size, 0 5 % Lo) and ramp shortening.4. The mechanical efficiency (the ratio of the power over the total energy rate) during ramp shortening had a maximum value of 0-36 at 1/5 VO; during staircase shortening, for any given shortening velocity, the mechanical efficiency was reduced compared with ramp shortening: with a staircase step of about 0 5 % Lo at 1/5 VO the efficiency was 0 2. 5.The results indicate that a cross-bridge is able to convert different quantities of energy into work depending on the different shortening protocol used. The fraction of energy dissipated as heat is larger during staircase shortening than during ramp shortening.

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“…As maximal tension is known to develop early in a skeletal or cardiac muscle twitch, and thereafter progressively and more slowly to decline, maximal external work can only be obtained if there is an early rapid increase in load followed by a progressive decline to match precisely the early rise and slower decline in tension. These conditions have been reproduced experimentally for skeletal muscle (2,35).…”

Section: Cn_1mentioning

confidence: 99%

“…In skeletal muscle at a particular initial length, and in heart muscle at a particular length and inotropic state, the extent and speed of shortening and the efficiency of the contraction depend upon the load (2)(3)(4)(5). In an earlier study we showed that in the normal conscious dog at rest the systemic load and the left ventricle were so matched that during contraction maximal external work was done and maximal power was transferred to the systemic circulation (6).…”

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confidence: 99%

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Load, Work, and Velocity of Muscle Shortening of the Left Ventricle in Normal and Abnormal Human Hearts*

Wilcken¹

1965

J. Clin. Invest.

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When a muscle contracts against a load less than one that would result in an isometric contraction, it shortens and does external work. In skeletal muscle at a particular initial length, and in heart muscle at a particular length and inotropic state, the extent and speed of shortening and the efficiency of the contraction depend upon the load (2-5). In an earlier study we showed that in the normal conscious dog at rest the systemic load and the left ventricle were so matched that during contraction maximal external work was done and maximal power was transferred to the systemic circulation (6). These conclusions were reached by studying successive contractions at different loads, but the load itself was not measured directly. The present study concerns the development of methods to measure the load in man, based on ventricular volume and pressure measurements. The relationships between external work and power transfer, velocity of muscle shortening, and load during left ventricular contraction were investigated. MethodsTheoretical considerations. The relation between force, and pressure and volume in the heart was recognized byStephen Hales (7). In recent years it has been outlined in detail by several authors (8, 9). The force acting radially on the inner surface of the ventricle at any time during systole is the product of the intraventricular pressure and surface area at that time. If the left ventricle is assumed to be a sphere (surface area = TrD2), the mean force acting on the ventricle over the whole of systole (PT) may be ex-* Submitted for publication November 23, 1964; accepted April 22, 1965. This work was supported by grant no. G.168 from the National Heart Foundation of Australia. Some of these data were presented at the February 1965 meeting of the Australian Physiological Society and appeared in abstract form (1). where FT is the mean force opposing ventricular ejection; P is the instantaneous intraventricular pressure during systole; D is the instantaneous diameter during systole of the ventricle, which is assumed to be spherical; t1 is the time at end diastole; and t2 is the time at end systole. This is taken as the point at the end of ventricular contraction at which the intraventricular pressure falls to its lowest level. If the walls and the cavity of the ventricle, which is assumed to be spherical, are considered to be transected by an imaginary plane that passes through the equator, the mean force tending to separate the ventricle into two hemispheres during contraction (FM) is related to the mean force opposing ejection (FT) in the ratio of r2/D2 (where r = radius), i.e., 0.25. This is the resultant mean force (FM) exerted by all the myocardial fibers perpendicular to this plane.In terms of the model there are periods at the beginning and at the end of systole, corresponding to isovolumetric contraction and relaxation, during which there is no fiber shortening and no change in D. The forces opposing ejection during these phases of systole can be determined if end-diastolic and end-systol...

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The mechanical efficiency of frog’s muscle

Cited by 68 publications

References 2 publications

Integrated electromyogram and oxygen uptake during positive and negative work.

Integrated electromyogram and oxygen uptake during positive and negative work.

Comparison of energy output during ramp and staircase shortening in frog muscle fibres.

Load, Work, and Velocity of Muscle Shortening of the Left Ventricle in Normal and Abnormal Human Hearts*

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