scholarly journals Further evidence against a force-velocity trade-off in muscle driven dynamic lever systems

2020 ◽  
Author(s):  
A. C. Osgood ◽  
G.P. Sutton ◽  
S. M. Cox
Keyword(s):  
Muscle Activation ◽  
Maximum Output ◽  
Moment Arm ◽  
Trade Off ◽  
Moment Arms ◽  
Lever System ◽  
Output Force ◽  
Total Impulse ◽  
Force Velocity ◽  
Static Conditions

AbstractLevers impose a force-velocity trade-off. In static conditions, a larger moment arm increases a muscle’s force capacity, and a smaller moment arm amplifies output velocity. However, muscle force is influenced by contractile velocity and fiber length, while contractile velocity is influenced by the inertial properties of the lever system. We hypothesize that these dynamic effects constrain the functional output of a muscle-lever system. We predict that there is an optimal moment arm to maximize output velocity for any given muscle-lever configuration. Here we test this hypothesis by computationally building and systematically modifying a simple lever system. We generated 3600 modifications of this model with muscles with varying optimal fiber lengths, moment arms and starting normalized muscle lengths. For each model we simulated the motion that results from 100% activation and extracted the maximum output lever velocity. In contrast to a tradeoff between force and velocity in a lever system, we found that there was, instead, an optimal moment arm which maximized both velocity and total impulse. Increasing output velocity always required increasing output force. From this we conclude that in a dynamic lever system where muscle activation is held constant, there is no tradeoff between force and velocity.

scholarly journals There is no trade-off between speed and force in a dynamic lever system

2010 ◽  
Vol 7 (3) ◽  
pp. 384-386 ◽  
Author(s):  
Matthew J. McHenry
Keyword(s):  
Small Distance ◽  
Static Equilibrium ◽  
Maximum Speed ◽  
Great Capacity ◽  
Trade Off ◽  
Input Force ◽  
Lever System ◽  
Output Force ◽  
Static Conditions ◽  
Stored Elastic Energy

Lever systems within a skeleton transmit force with a capacity determined by the mechanical advantage, A. A is the distance from input force to a joint, divided by the distance from the joint to the output force. A lever with a relatively high A in static equilibrium has a great capacity to generate force but moves a load over a small distance. Therefore, the geometry of a skeletal lever presents a trade-off between force and speed under quasi-static conditions. The present study considers skeletal dynamics that do not assume static equilibrium by modelling kicking by a locust leg, which is powered by stored elastic energy. This model predicts that the output force of this lever is proportional to A , but its maximum speed is independent of A . Therefore, no trade-off between force and velocity exists in a lever system with spring-mass dynamics. This demonstrates that the motion of a skeleton depends on the major forces that govern its dynamics and cannot be inferred from skeletal geometry alone.

A New Inertia-Based Linear Stepper Motor for Micro-Surgical Procedures

1998 ◽  
Author(s):  
Raed N. Rizq ◽  
David J. Peichel ◽  
David R. Wulfman ◽  
Arthur G. Erdman ◽  
Dennis L. Polla
Keyword(s):  
Stepper Motor ◽  
Maximum Output ◽  
Total Displacement ◽  
Output Force ◽  
Mems Technology ◽  
Surgical Device ◽  
Consistent Performance ◽  
Precision Motion ◽  
Small Implants ◽  
Device Test

Abstract A new hand held surgical device intended to aid physicians in microsurgery is reported. This device provides a means for delivering small implants through the use of a precision motion linear stepper motor fabricated from silicon and piezoelectric components. The stepper motor described here utilizes the inertial properties of a moving mass as part of the actuation process. Micro Electromechanical Systems-based (MEMS) technology is used in building the device. Test instruments have delivered over fifty implants with consistent performance. Typically the test instruments have attained 1.2 mm/s advancement speeds against 3 Newton resistance loads, a maximum output force of 4.6 Newtons, and maximum total displacement of 38 mm.

Effect of airway inflammation on smooth muscle shortening and contractility in guinea pig trachealis

1993 ◽  
Vol 265 (6) ◽  
pp. L549-L554 ◽  
Author(s):  
R. W. Mitchell ◽  
I. M. Ndukwu ◽  
K. Arbetter ◽  
J. Solway ◽  
A. R. Leff
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Neurogenic Inflammation ◽  
Isometric Force ◽  
Electrical Field Stimulation ◽  
Shortening Velocity ◽  
Lever System ◽  
Force Velocity

We studied the effect of either 1) immunogenic inflammation caused by aerosolized ovalbumin or 2) neurogenic inflammation caused by aerosolized capsaicin in vivo on guinea pig tracheal smooth muscle (TSM) contractility in vitro. Force-velocity relationships were determined for nine epithelium-intact TSM strips from ovalbumin-sensitized (OAS) vs. seven sham-sensitized controls and TSM strips for seven animals treated with capsaicin aerosol (Cap-Aer) vs. eight sham controls. Muscle strips were tethered to an electromagnetic lever system, which allowed isotonic shortening when load clamps [from 0 to maximal isometric force (Po)] were applied at specific times after onset of contraction. Contractions were elicited by supramaximal electrical field stimulation (60 Hz, 10-s duration, 18 V). Optimal length for each muscle was determined during equilibration. Maximal shortening velocity (Vmax) was increased in TSM from OAS (1.72 +/- 0.46 mm/s) compared with sham-sensitized animals (0.90 +/- 0.15 mm/s, P < 0.05); Vmax for TSM from Cap-Aer (0.88 +/- 0.11 mm/s) was not different from control TSM (1.13 +/- 0.08 mm/s, P = NS). Similarly, maximal shortening (delta max) was augmented in TSM from OAS (1.01 +/- 0.15 mm) compared with sham-sensitized animals (0.72 +/- 0.14 mm, P < 0.05); delta max for TSM from Cap-Aer animals (0.65 +/- 0.11 mm) was not different from saline aerosol controls (0.71 +/- 0.15 mm, P = NS). We demonstrate Vmax and delta max are augmented in TSM after ovalbumin sensitization; in contrast, neurogenic inflammation caused by capsaicin has no effect on isolated TSM contractility in vitro. These data suggest that airway hyperresponsiveness in vivo that occurs in association with immunogenic or neurogenic inflammation may result from different effects of these types of inflammation on airway smooth muscle.

Analysis of the mero-carpopodite joint of the American lobster and snow crab. II. Kinematics, morphometrics and moment arms

2003 ◽  
Vol 83 (6) ◽  
pp. 1249-1259 ◽  
Author(s):  
S.C. Mitchell ◽  
M.E. DeMont
Keyword(s):  
Joint Angle ◽  
Snow Crab ◽  
Moment Arm ◽  
Scaling Effects ◽  
Joint Angles ◽  
Positive Allometry ◽  
Moment Arms ◽  
Arm Reaching ◽  
Flexion Extension ◽  
The Moment

This research reports on the kinematics of lobster and snow crab walking, documents changes in the moment arms of the mero-carpopodite joint during rotation, and examines scaling effects of morphological and mechanical variables in these crustacean species. Forward walking lobsters and lateral walking crabs were recorded and images analysed to describe the kinematics of these animals, and subsequently morphometric and moment arm measurements made. During forward walking the lobster maintains fixed mero-carpopodite joint angles during both the power and recovery strokes, though each of the walking legs maintains different joint angles. Legs 3 and 5 are maintained at angles which appear to equalize the flexor and extensor moment arms, and leg 4 joint angle appears to maximize the extensor moment arm. The snow crab has a joint excursion angle of between approximately 50° to 150° and, during flat bed walking, the leading and trailing legs move through similar excursion angles. The length of the meropodite for both species are longer for the anterior two leg pairs relative to the posterior two pairs and the rate of growth of the meropodite is largely isometric for the lobster while consistently increases with positive allometry in the crab. The flexor and extensor moment arms generated as the joint undergoes flexion/extension show two distinct patterns with the extensor moment arm being maximized at relatively low joint angles (55°–115°) and the flexor moment arm reaching a plateau at joint extension with angles between 95° and 155°. The flexor apodeme possesses the largest moment arms in all legs for both species, suggesting the flexors are able to generate greater torques. It appears that, mechanically, these laterally moving animals may be ‘pulling’ with the leading legs to a greater extent than ‘pushing’ with the trailing legs.

scholarly journals Electrochemical Coupled Analysis of a Micro Piezo-Driven Focusing Mechanism

Micromachines ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 216 ◽  
Author(s):  
Chong Li ◽  
Kang Liang ◽  
Wei Zhong ◽  
Jiwen Fang ◽  
Lining Sun ◽  
...  
Keyword(s):  
Electromechanical Coupling ◽  
Response Speed ◽  
Coupled Analysis ◽  
Maximum Output ◽  
Driving Voltage ◽  
Matlab Simulation ◽  
Output Performance ◽  
Output Force ◽  
Drive Theory ◽  
Output Characteristics

In order to improve the response speed and output force of the camera focusing mechanism, the authors proposed a novelty micro focusing mechanism based on piezoelectric driving, which has the characteristics of rapid response, high precision positioning and large displacement focusing. In this paper, the operating principle of the proposed focusing mechanism is presented. Using the piezoelectric output characteristic, the movable tooth drive theory and the screw drive theory, the electromechanical coupling mechanical model and equations of the piezoelectric focusing mechanism are established. Through MATLAB simulation, the output characteristics of the piezoelectric focusing mechanism are calculated. The results indicate that the maximum thrust force of the lens and the maximum output torque of the movable tooth drive for the piezoelectric focusing mechanism are 562.5 N and 1.16 Nm, respectively. Furthermore, the driving voltage directly affects the output performance of the piezoelectric focusing mechanism. These results can be utilized both to optimize the dimensions and improve the overall performance of the piezo-driven focusing mechanism.

scholarly journals Analyzing Moment Arm Profiles in a Full-Muscle Rat Hindlimb Model

Biomimetics ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 10 ◽  
Author(s):  
Fletcher Young ◽  
Christian Rode ◽  
Alex Hunt ◽  
Roger Quinn
Keyword(s):  
Three Dimensional ◽  
Joint Torque ◽  
Fundamental Aspect ◽  
Moment Arm ◽  
Critical Aspect ◽  
Step Cycle ◽  
Moment Arms ◽  
3D Space ◽  
Torque Generation ◽  
Torque Moment

Understanding the kinematics of a hindlimb model is a fundamental aspect of modeling coordinated locomotion. This work describes the development process of a rat hindlimb model that contains a complete muscular system and incorporates physiological walking data to examine realistic muscle movements during a step cycle. Moment arm profiles for selected muscles are analyzed and presented as the first steps to calculating torque generation at hindlimb joints. A technique for calculating muscle moment arms from muscle attachment points in a three-dimensional (3D) space has been established. This model accounts for the configuration of adjacent joints, a critical aspect of biarticular moment arm analysis that must be considered when calculating joint torque. Moment arm profiles from isolated muscle motions are compared to two existing models. The dependence of biarticular muscle’s moment arms on the configuration of the adjacent joint is a critical aspect of moment arm analysis that must be considered when calculating joint torque. The variability in moment arm profiles suggests changes in muscle function during a step.

scholarly journals Muscle fatigue examined at different temperatures in experiments on intact mammalian (rat) muscle fibers

2009 ◽  
Vol 106 (2) ◽  
pp. 378-384 ◽  
Author(s):  
H. Roots ◽  
G. Ball ◽  
J. Talbot-Ponsonby ◽  
M. King ◽  
K. McBeath ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Power Output ◽  
Force Depression ◽  
Output Force ◽  
Different Temperatures ◽  
Force Velocity ◽  
C 30 ◽  
C 50 ◽  
Shortening Contractions

In experiments on small bundles of intact fibers from a rat fast muscle, in vitro, we examined the decline in force in repeated tetanic contractions; the aim was to characterize the effect of shortening and of temperature on the initial phase of muscle fatigue. Short tetanic contractions were elicited at a control repetition rate of 1/60 s, and fatigue was induced by raising the rate to 1/5 s for 2–3 min, both in isometric mode (no shortening) and in shortening mode, in which each tetanic contraction included a ramp shortening at a standard velocity. In experiments at 20°C ( n = 12), the force decline during a fatigue run was 25% in the isometric mode but was significantly higher (35%) in the shortening mode. In experiments at different temperatures (10–30°C, n = 11), the tetanic frequency and duration were adjusted as appropriate, and for shortening mode, the velocity was adjusted for maximum power output. In isometric mode, fatigue of force was significantly less at 30°C (∼20%) than at 10°C (∼30%); the power output (force × velocity) was >10× higher at 30°C than at 10°C, and power decline during a fatigue run was less at 30°C (∼20–30%) than at 10°C (∼50%). The finding that the extent of fatigue is increased with shortening contractions and is lower at higher temperatures is consistent with the view that force depression by inorganic phosphate, which accumulates within fibers during activity, may be a primary cause of initial muscle fatigue.

Mechanical and photosynthetic constraints on the evolution of plant shape

Paleobiology ◽  
1984 ◽  
Vol 10 (1) ◽  
pp. 79-101 ◽  
Author(s):  
Karl J. Niklas ◽  
Vincent Kerchner
Keyword(s):  
Photosynthetic Efficiency ◽  
Growth Habit ◽  
Three Dimensional ◽  
Main Axis ◽  
Moment Arm ◽  
Total Moment ◽  
Moment Arms ◽  
Branching Patterns ◽  
Upper Silurian ◽  
Lateral Branches

A computer model is presented which is capable of calculating both the photosynthetic efficiency (I) of any specified plant shape and the stress related to the total moment arm (M) imposed on vertical branching patterns. Computer simulations indicate that a flattened plant thallus and an erect branching growth habit are two plant shapes capable of optimizing photosynthetic efficiency during indeterminate growth. These two morphologies have geometric analogues in the dorsiventral thalli of some bryophytes and in the vertical axes of mosses and tracheophytes, respectively.Extension of the model to complex, three-dimensional branching patterns indicates that I and I/M are maximized when branching is overtopped (treelike, with lateral branches on a main axis) and when lateral branching systems are planated (frondlike). Geometric alterations of branching patterns that result in optimization of I and I/M can be simulated by computer and are shown to be similar to morphologic alterations attending the early evolution of vascular land plants. It is suggested that a number of major evolutionary trends seen in Upper Silurian to Upper Devonian times can be expressed in terms of optimizing the display of photosynthetic tissues (I) or the balance between photosynthetic efficiency and incurred moment arms (I/M).

Muscle Strengths and Musculoskeletal Geometry of the Upper Limb

1979 ◽  
Vol 8 (1) ◽  
pp. 41-48 ◽  
Author(s):  
A A Amis ◽  
D Dowson ◽  
V Wright
Keyword(s):  
Upper Limb ◽  
Cross Sections ◽  
Wrist Joint ◽  
Elbow Flexion ◽  
Reliable Data ◽  
Moment Arm ◽  
Joint Replacements ◽  
Moment Arms ◽  
Joint Forces

A survey of past literature has shown that there is a lack of reliable data for use in prediction of joint forces in the upper limb although this is desirable when developing joint replacements. Upper limb geometry has been analysed, leading to muscle moment arm data at the wrist and elbow. The variation of these moment arms during elbow flexion has also been examined. Analysis of the dimensions of muscles has enabled their relative strengths to be predicted, based on their ‘physiological cross-sections’. When used in conjuction with published emg data, this information will enable elbow and wrist joint forces to be estimated more realistically than has previously been possible.

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