Hurry Up and Get Out of the Way! Exploring the Limits of Muscle-Based Latch Systems for Power Amplification

Abstract Animals can amplify the mechanical power output of their muscles as they jump to escape predators or strike to capture prey. One mechanism for amplification involves muscle–tendon unit (MT) systems in which a spring element (series elastic element [SEE]) is pre-stretched while held in place by a “latch” that prevents immediate transmission of muscle (or contractile element, CE) power to the load. In principle, this storage phase is followed by a triggered release of the latch, and elastic energy released from the SEE enables power amplification (PRATIO=PLOAD/PCE,max >1.0), whereby the peak power delivered from MT to the load exceeds the maximum power limit of the CE in isolation. Latches enable power amplification by increasing the muscle work generated during storage and reducing the duration over which that stored energy is released to power a movement. Previously described biological “latches” include: skeletal levers, anatomical triggers, accessory appendages, and even antagonist muscles. In fact, many species that rely on high-powered movements also have a large number of muscles arranged in antagonist pairs. Here, we examine whether a decaying antagonist force (e.g., from a muscle) could be useful as an active latch to achieve controlled energy transmission and modulate peak output power. We developed a computer model of a frog hindlimb driven by a compliant MT. We simulated MT power generated against an inertial load in the presence of an antagonist force “latch” (AFL) with relaxation time varying from very fast (10 ms) to very slow (1000 ms) to mirror physiological ranges of antagonist muscle. The fastest AFL produced power amplification (PRATIO=5.0) while the slowest AFL produced power attenuation (PRATIO=0.43). Notably, AFLs with relaxation times shorter than ∼300 ms also yielded greater power amplification (PRATIO>1.20) than the system driving the same inertial load using only an agonist MT without any AFL. Thus, animals that utilize a sufficiently fast relaxing AFL ought to be capable of achieving greater power output than systems confined to a single agonist MT tuned for maximum PRATIO against the same load.

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On the mechanical power output comparisons of cone dielectric elastomer actuators

IEEE/ASME Transactions on Mechatronics ◽

10.1109/tmech.2021.3054460 ◽

2021 ◽

pp. 1-1

Author(s):

Chongjing Cao ◽

Lijin Chen ◽

Wenke Duan ◽

Thomas L. Hill ◽

Bo Li ◽

...

Keyword(s):

Power Output ◽

Dielectric Elastomer ◽

Mechanical Power ◽

Dielectric Elastomer Actuators ◽

Mechanical Power Output

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Effect of Accommodating Elastic Bands on Mechanical Power Output during Back Squats

Sports ◽

10.3390/sports6040151 ◽

2018 ◽

Vol 6 (4) ◽

pp. 151 ◽

Cited By ~ 1

Author(s):

Takafumi Kubo ◽

Kuniaki Hirayama ◽

Nobuhiro Nakamura ◽

Mitsuru Higuchi

Keyword(s):

Power Output ◽

Random Order ◽

Mechanical Power ◽

Muscular Force ◽

Force Output ◽

Elastic Band ◽

Free Weight ◽

Mechanical Power Output ◽

Elastic Bands ◽

Acceleration And Deceleration

The aim of this study was to investigate whether accommodating elastic bands with barbell back squats (BSQ) increase muscular force during the deceleration subphase. Ten healthy men (mean ± standard deviation: Age: 23 ± 2 years; height: 170.5 ± 3.7 cm; mass: 66.7 ± 5.4 kg; and BSQ one repetition maximum (RM): 105 ± 23.1 kg; BSQ 1RM/body mass: 1.6 ± 0.3) were recruited for this study. The subjects performed band-resisted parallel BSQ (accommodating elastic bands each sides of barbell) with five band conditions in random order. The duration of the deceleration subphase, mean mechanical power, and the force and velocity during the acceleration and deceleration subphases were calculated. BSQ with elastic bands elicited greater mechanical power output, velocity, and force during the deceleration subphase, in contrast to that elicited with traditional free weight (p < 0.05). BSQ with elastic bands also elicited greater mechanical power output and velocity during the acceleration subphase. However, the force output during the acceleration subphase using an elastic band was lesser than that using a traditional free weight (p < 0.05). This study suggests that BSQ with elastic band elicit greater power output during the acceleration and deceleration subphases.

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Pinacidil-primed ATP-sensitive potassium channels mediate feedback control of mechanical power output in isolated myocardium of rats and guinea pigs

European Journal of Pharmacology ◽

10.1016/j.ejphar.2009.11.013 ◽

2010 ◽

Vol 628 (1-3) ◽

pp. 116-127 ◽

Cited By ~ 1

Author(s):

Diethart Schmid ◽

Dawid L. Staudacher ◽

Christian A. Plass ◽

Hans G. Loew ◽

Eva Fritz ◽

...

Keyword(s):

Feedback Control ◽

Potassium Channels ◽

Power Output ◽

Guinea Pigs ◽

Mechanical Power ◽

Mechanical Power Output ◽

Isolated Myocardium

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Power output by an asynchronous flight muscle from a beetle

Journal of Experimental Biology ◽

10.1242/jeb.203.17.2667 ◽

2000 ◽

Vol 203 (17) ◽

pp. 2667-2689 ◽

Cited By ~ 7

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.

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Total power output generated during dynamic knee extensor exercise at different contraction frequencies

Journal of Applied Physiology ◽

10.1152/jappl.2000.89.5.1912 ◽

2000 ◽

Vol 89 (5) ◽

pp. 1912-1918 ◽

Cited By ~ 23

Author(s):

Richard A. Ferguson ◽

Per Aagaard ◽

Derek Ball ◽

Anthony J. Sargeant ◽

Jens Bangsbo

Keyword(s):

Power Output ◽

Accurate Determination ◽

Knee Extensor ◽

Mechanical Efficiency ◽

Muscle Group ◽

Total Power ◽

Mechanical Power Output ◽

External Power ◽

Power Outputs ◽

Total Power Output

A novel approach has been developed for the quantification of total mechanical power output produced by an isolated, well-defined muscle group during dynamic exercise in humans at different contraction frequencies. The calculation of total power output comprises the external power delivered to the ergometer (i.e., the external power output setting of the ergometer) and the “internal” power generated to overcome inertial and gravitational forces related to movement of the lower limb. Total power output was determined at contraction frequencies of 60 and 100 rpm. At 60 rpm, the internal power was 18 ± 1 W (range: 16–19 W) at external power outputs that ranged between 0 and 50 W. This was less ( P < 0.05) than the internal power of 33 ± 2 W (27–38 W) at 100 rpm at 0–50 W. Moreover, at 100 rpm, internal power was lower ( P < 0.05) at the higher external power outputs. Pulmonary oxygen uptake was observed to be greater ( P< 0.05) at 100 than at 60 rpm at comparable total power outputs, suggesting that mechanical efficiency is lower at 100 rpm. Thus a method was developed that allowed accurate determination of the total power output during exercise generated by an isolated muscle group at different contraction frequencies.

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The weak link: do muscle properties determine locomotor performance in frogs?

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2010.0326 ◽

2011 ◽

Vol 366 (1570) ◽

pp. 1488-1495 ◽

Cited By ~ 34

Author(s):

Thomas J. Roberts ◽

Emily M. Abbott ◽

Emanuel Azizi

Keyword(s):

Muscle Mass ◽

Power Output ◽

Muscle Power ◽

Locomotor Performance ◽

Jump Performance ◽

Leopard Frogs ◽

Ideal System ◽

Mechanical Power Output ◽

Osteopilus Septentrionalis ◽

Jump Power

Muscles power movement, yet the conceptual link between muscle performance and locomotor performance is poorly developed. Frog jumping provides an ideal system to probe the relationship between muscle capacity and locomotor performance, because a jump is a single discrete event and mechanical power output is a critical determinant of jump distance. We tested the hypothesis that interspecific variation in jump performance could be explained by variability in available muscle power. We used force plate ergometry to measure power produced during jumping in Cuban tree frogs ( Osteopilus septentrionalis ), leopard frogs ( Rana pipiens ) and cane toads ( Bufo marinus ). We also measured peak isotonic power output in isolated plantaris muscles for each species. As expected, jump performance varied widely. Osteopilus septentrionalis developed peak power outputs of 1047.0 ± 119.7 W kg −1 hindlimb muscle mass, about five times that of B. marinus (198.5 ± 54.5 W kg −1 ). Values for R. pipiens were intermediate (543.9 ± 96.2 W kg −1 ). These differences in jump power were not matched by differences in available muscle power, which were 312.7 ± 28.9, 321.8 ± 48.5 and 262.8 ± 23.2 W kg −1 muscle mass for O. septentrionalis , R. pipiens and B. marinus , respectively. The lack of correlation between available muscle power and jump power suggests that non-muscular mechanisms (e.g. elastic energy storage) can obscure the link between muscle mechanical performance and locomotor performance.

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