Built for Jumping: the Design of the Frog Muscular System

Lutz, Gordon J.; Rome, Lawrence C.

doi:10.1126/science.8278808

Cited by 224 publications

(176 citation statements)

References 21 publications

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“…As a result, an important caveat to our results is that the force-length curve of the muscle is characterized under maximal stimulation. One advantage to frog jumping as a model system is that an anti-predator behaviour like a frog jump likely involves maximal recruitment (Lutz & Rome 1994). However, even under conditions of submaximal recruitment, a muscle's force-length curve should accurately describe the effect of length on force in the subset of fibres that are active.…”

Section: Discussion (A) Operating Lengths Of the Frog Plantarismentioning

confidence: 99%

Muscle performance during frog jumping: influence of elasticity on muscle operating lengths

2010

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A fundamental feature of vertebrate muscle is that maximal force can be generated only over a limited range of lengths. It has been proposed that locomotor muscles operate over this range of lengths in order to maximize force production during movement. However, locomotor behaviours like jumping may require muscles to shorten substantially in order to generate the mechanical work necessary to propel the body. Thus, the muscles that power jumping may need to shorten to lengths where force production is submaximal. Here we use direct measurements of muscle length in vivo and muscle force-length relationships in vitro to determine the operating lengths of the plantaris muscle in bullfrogs (Rana catesbeiana) during jumping. We find that the plantaris muscle operates primarily on the descending limb of the force-length curve, resting at long initial lengths (1.3 + 0.06 L o ) before shortening to muscle's optimal length (1.03 + 0.05 L o ). We also compare passive force-length curves from frogs with literature values for mammalian muscle, and demonstrate that frog muscles must be stretched to much longer lengths before generating passive force. The relatively compliant passive properties of frog muscles may be a critical feature of the system, because it allows muscles to operate at long lengths and improves muscles' capacity for force production during a jump.

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Section: Discussion (A) Operating Lengths Of the Frog Plantarismentioning

confidence: 99%

Muscle performance during frog jumping: influence of elasticity on muscle operating lengths

2010

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“…It must further be remarked that Lutz and Rome (1994) argued that in vivo limb extensors in frogs actually act at the plateau of their L-T-curves.…”

Section: Discussionmentioning

confidence: 99%

“…There is no effect of actuator length on force output (i.e. the muscle-like actuator always works at optimal 'filament' overlap; Lutz and Rome, 1994) 3333Forward dynamical modelling of a single kick is carried out numerically (Euler integration) with time steps equal to 5x10 -4 s. The general equation of motion used for both body and feet is:…”

Section: Methods: Model Descriptionmentioning

confidence: 99%

Environmentally induced mechanical feedback in locomotion: Frog performance as a model

Aerts

Nauwelaerts

2009

Journal of Theoretical Biology

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A c c e p t e d m a n u s c r i p t 2 AbstractAt first glance, the strategy for generating propulsive impulses for both jumping and swimming in frogs is quite similar. Both modes rely on powerful extension of the hind limbs.However, in Rana esculenta (the semi-aquatic green frog), propulsive impulses for jumping were found to be much larger than those generated during swimming (Nauwelaerts and Aerts, 2003). The hypothesis that differences in propulsive impulse between swimming and jumping are largely caused by specific environmental constraints rather than being due to changes in motor control is tested in the present study. To assess this question, the actuator of a simple mathematical model, mimicking a frog with symmetrically kicking hind limbs, is first tuned to perform frog-like jumps. Next, the same actuator activation is applied to drive the model in an 'aquatic environment'. Despite the entirely identical activation, the resulting in silico propulsive swimming impulse was less than half that produced during jumping, just as observed in vivo. Although duration of limb extension is similar for both locomotor modes (both in vivo and in silico), this conspicuous difference in model behaviour is entirely explained by the actuator working at different positions along its force-velocity curve. These findings suggest that the same environmentally induced effects are also involved in real swimming and jumping as well, thus explaining the apparent difference in performance level.

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“…As a consequence of decreasing V/V max with body size, muscle power should trace the predicted n-shaped power curve 13 . Figure 2c shows the proportion of maximum power available to a muscle over the range of muscle-shortening velocities we have observed for frogs of different body masses (see 'In vivo muscle-shortening velocities' below).…”

Section: Resultsmentioning

confidence: 99%

“…This second property can also be represented as a power-velocity curve (power ¼ force Â velocity), where power is maximal at B1/3 of the maximum muscle-shortening velocity (V max ), but decreases at greater and lesser velocities, producing an 'n-shaped' curve. Thus, for the muscle to produce its maximal mechanical power, it must be maximally stimulated, be near 100% overlap and operate at B1/3 V max 11,13 . However, below we derive a scaling model, which suggests that these criteria cannot be maintained across all body sizes, instead maximum potential muscle power may vary with body size, producing an n-shaped relationship between power and body mass (M).…”

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confidence: 99%

Muscle function and hydrodynamics limit power and speed in swimming frogs

Clemente

Richards²

2013

Nat Commun

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Studies of the muscle force-velocity relationship and its derived n-shaped power-velocity curve offer important insights into muscular limits of performance. Given the power is maximal at 1/3 V max , geometric scaling of muscle force coupled with fluid drag force implies that this optimal muscle-shortening velocity for power cannot be maintained across the natural body-size range. Instead, muscle velocity may decrease with increasing body size, conferring a similar n-shaped power curve with body size. Here we examine swimming speed and muscle function in the aquatic frog Xenopus laevis. Swimming speed shows an n-shaped scaling relationship, peaking at 47.35 g. Further, in vitro muscle function of the ankle extensor plantaris longus also shows an optimal body mass for muscle power output (47.27 g), reflecting that of swimming speed. These findings suggest that in drag-based aquatic systems, muscle-environment interactions vary with body size, limiting both the muscle's potential to produce power and the swimming speed.

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Built for Jumping: the Design of the Frog Muscular System

Cited by 224 publications

References 21 publications

Muscle performance during frog jumping: influence of elasticity on muscle operating lengths

Muscle performance during frog jumping: influence of elasticity on muscle operating lengths

Environmentally induced mechanical feedback in locomotion: Frog performance as a model

Muscle function and hydrodynamics limit power and speed in swimming frogs

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