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Functional Properties of Muscle
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
It may be noted that the maximum stress, or force per unit area, that a muscle can develop depends, strictly speaking, on the length of the A bands, that is the length of the thick filaments, which correlates linearly with the resting sarcomere length (Section 9.1.2). Hence, the longer this length is, the larger is the number of cross bridges that can form within each sarcomere and the greater is the maximum stress produced. Vertebrate and insect flight muscles have sarcomeres of 2–4 µm length, which yield stresses of 100–300 kN/m2. On the other hand, muscles that close the claws of some crustaceans have sarcomeres of 14–18 µm length and a stress as high as 2000 kN/m2, the largest in the animal kingdom. Crustaceans need very strong claws because they feed on hard-shelled prey.
Biomechanical Modeling of Muscular Contraction
Published in Yuehong Yin, Biomechanical Principles on Force Generation and Control of Skeletal Muscle and their Applications in Robotic Exoskeleton, 2020
The frequency of the length cycle is fixed at 1 Hz, and the excursion amplitude is set to be 4% L0 (0.044 μm), which falls in the reasonable range (2.3%−7.3%) of the amplitudes used in the experiments [92]. The periodic burst-firing stimulus is simulated using a square pulse train of f with a unit pulse height and a pulse width of 100 ms. This corresponds to the effect of 3–4 APs within a burst, which is within the reasonable range for mammalian muscle during cyclic contractions. Here, we define the stimulus phase (PS) as the ratio between the delay of the time corresponding to the peak activation degree after the time of maximum sarcomere length and the whole cycle period. PS is expressed as a percentage. Figure 2.47a shows the transients of both force and activation degree of a half-sarcomere with the stimulus train of PS = 10.4%, and Figure 2.47b shows several force–length orbits with different PS. It is noteworthy that for each PS, five stimulus cycles are used in order to let the orbit stabilize and converge. The key features as well as the trend of the variation of the orbits’ structure with the changes of the stimulus phase are highly consistent with the experimental results (Figure 2.47c), while the differences between the detailed shapes of simulated and experimental orbits are due to different muscle types or parameters because in [92], the insect flight muscles were used. The time for one iteration in the simulation is approximately 0.73 μs.
Vortices
Published in Wen-Jei Yang, Handbook of Flow Visualization, 2018
Mushroom formation by pitching airfoils should have some relevance to bird- and insect-flight propulsion. Even more relevance can be expected from investigations of simultaneously pitching and plunging airfoils, which could serve as a crude two-dimensional model of wing flapping.
Propulsive forces on water polo players’ feet from eggbeater kicking estimated by pressure distribution analysis
Published in Sports Biomechanics, 2020
Eisuke Kawai, Takaaki Tsunokawa, Hiroyuki Sakaue, Hideki Takagi
The large pressure decrease on the dorsal side of the foot segments may be elucidated by Takagi et al.’s (2014) findings. They reported a leading-edge vortex around the second finger on the dorsal side of a swimmer’s hand and found that this vortex caused a large decrease in dorsal side pressure during the in-scull phase of sculling. Mainly found in insect flight motions, leading-edge vortices occur on the front side (preceding part) of the wing and generate large negative pressures on the upper part of the wing (Ellington et al., 1996). During the down kick of the eggbeater kick, the preceding part of the foot is the first toe side (Sanders, 1999a, 1999b). In this study, although we could not elucidate the mechanism because the flow was not visualised, the pressure decreases on the dorsal side of the foot (especially segment 1) may have attributed to a leading-edge vortex comparable to those reported in studies of hand sculling and insect flight motion.
A simple vortex approach to complex two-wing unsteady flapping problems in 2D applied to insect flight study
Published in European Journal of Computational Mechanics, 2018
Mitsunori Denda, Roberta Shapiro, Justin Wong
The effect of the insect flight speed, , is incorporated by moving the wing itself in the direction opposite to the air velocity under zero ambient velocity. The non-zero ambient velocity can be superimposed over this. For a constant air velocity, the total translational motion of the wing is obtained by superimposing the contributions, (lunge) and (heave), from the flapping motion and the air velocity to give , where is the time.
Kinematic and kinetic parameters to identify water polo players’ eggbeater kick techniques
Published in Sports Biomechanics, 2021
Eisuke Kawai, Tomohiro Gonjo, Hideki Takagi
In a previous study (Kawai et al., 2020), it was reported that the propulsive force during the eggbeater kick increased by the pressure difference between the plantar and dorsal side of the foot, which was mainly related to the decrease in pressure on the dorsal side. This phenomenon was similarly observed in both feet in this study (Figure 2(b)). The significant pressure difference in segment 1 (around the first toe) due to negative pressure on the dorsal side of the foot (Figure 2(c)) may be explained by the leading-edge vortex that is an essential factor in insect flight. These vortices are produced on the front side (leading part) of the wing and generate large negative pressures on the upper part of the wing (Ellington et al., 1996). Takagi et al. (2014) also observed a leading-edge vortex around the second finger on the dorsal side of a human swimmer’s hand and found that this vortex caused a large decrease in dorsal side pressure during the in-scull phase of sculling. With the exception of the beginning of the kick and recovery, the leading part of the foot during the eggbeater kick is the first toe side, which supports the possibility of lower negative pressure around the first toe produced by the leading-edge vortex. On the other hand, segment 3 (around the fifth toe) is far from the leading part, suggesting that the effect of the generated vortex is small. This might explain why the pressure difference between the plantar and dorsal side of this part of the foot was hardly observed, and consequently, the contribution to propulsion was also small. In fact, in hand sculling, the pressure difference around the fifth finger is also very small during the in-scull phase (Takagi et al., 2014). For effective propulsion during eggbeater kicking, water flow should be directed from the first toe side during the out-kick and the first half of the in-kick, for which the hip (flexion, abduction, internal rotation) and ankle (supination/pronation) movements are important (Homma & Homma, 2005; Oliveira et al., 2015). In addition, the negative propulsive force during the second half of the in-kick (recovery motion) should be minimised (Figure 2(a)).