In lengthening (eccentric) muscle actions, the force velocity relationship is the . These differences between free weights and pneumatic resistance mean that. On the descending limb of the force-length relationship, this will result .. the force-velocity relationship  and the history (or time)-dependent Even though these properties represent the basis for all muscle . to make statements about the mechanics of muscles, for example to Cells Tissues Organs. Which of the following is a behavioral property of muscle tissue? . Which of the following statements represents the force-velocity relationship for muscle tissue.
I was invited to this conference with the mandate to chair a session on skeletal muscle mechanics, energetics and plasticity. The task given to me was to identify some of the major questions and problems in skeletal muscle mechanics and present those in a concise manner and understandable to the non-expert.
I must admit this was a rather difficult task for a person like me who believes that we know little to nothing about muscle contraction on the molecular levelwhat the basic muscle properties are except for the most standardized conditionsand how muscles function in the in vivo, freely moving system under non-steady-state, submaximal conditions.
Force velocity relationship – Strength & Conditioning Research
In the end, I identified three topics that I presented and discussed. At the end, I settled on topics that are highly controversial, often misunderstood, and close to my heart. They may be summarized as follows: In the following, I will be discussing these topics concisely by raising one or more problems in the area, provide possible solutions, and may make some suggestions for future challenges that, if solved, may improve our understanding of skeletal muscle biomechanics and movement control.
Following my introductory manuscript will be four manuscripts supplied by the participants of the muscle workshop: Their contributions are focused on specific problems and challenges faced today by researchers in muscle mechanics and they will add important considerations to the discussion below.
I sincerely hope that the BANCOM conference will be repeated in another twenty years, and that we can reflect on which of the challenges, questions and problems have been solved.
Hopefully, the set of papers presented here will form a framework for what some of the young people entering this field may consider worthwhile projects. Mechanisms of muscle contraction, sarcomere stability and mechanics The cross-bridge theory description When opening a textbook of muscle physiology and searching for how muscles contract, we are inevitably exposed to the cross-bridge theory of contraction.
This theory was first proposed in a rather obscure journal Progress in Biophysics and Biophysical Chemistry that only existed for a brief period of time. The founding editor of that journal was a friend of Andrew Huxley, and so he asked his friend to make a contribution, and Huxley [ 1 ] submitted his ideas of how muscles may contract.
As time progresses, the plotted points trace the shape of the work loop. The direction in which the work loop is traced through time is a critical feature of the work loop. As the muscle shortens while generating a tensile force i. As the muscle lengthens while still generating a tensile forcethe muscle is performing negative work or, alternatively, that positive work is being performed on the muscle.
Thus a muscle generating force while shortening is said to output 'positive work' i.Length - Tension Relationship (Video 2.6) - PhysioStasis
Over an entire cycle, there is typically some positive, and some negative work; if the overall cycle is counter-clockwise vs. When landing, however, the same muscles absorb work to decrease the body's speed, yielding clockwise work loops. Furthermore, a muscle can produce positive work followed by negative work or vice versa within a shortening-lengthening cycle, causing a 'figure 8' work loop shape containing both clockwise and counter-clockwise segments. In a typical work-generating instance, the muscle shows a rapid curvilinear rise in force as it shortens, followed by a slower decline during or shortly before the muscle begins the lengthening phase of the cycle.
The area beneath the shortening curve upper curve gives the total work done by the shortening muscle, while the area beneath the lengthening curve lower curve represents the work absorbed by the muscle and turned into heat done by either environmental forces or antagonistic muscles.
Which of the following statements represents the force-velocity relationship for muscle tissue?
Subtracting the latter from the former gives the net mechanical work output of the muscle cycle, and dividing that by the cycle duration gives net mechanical power output. For example, a muscle that generates force without changing length isometric contraction will show a vertical line 'work loop'. Reciprocally, a muscle that shortens without changing force isotonic contraction will show a horizontal line 'work loop'.
Finally, a muscle can behave like a spring which extends linearly as a force is applied. This final case would yield a slanted straight line 'work loop' where the line slope is the spring stiffness. The experimental technique described below applies both to in vitro and in situ approaches.
Experimental setup[ edit ] Following humane procedures approved by IACUCthe muscle is isolated from the animal or prepared in situattached to the muscle testing apparatus and bathed in oxygenated Ringer's solution or Krebs-Henseleit solution maintained at a constant temperature. While the isolated muscle is still living, the experimenter then applies two manipulations to test muscle function: To elicit muscle contraction, the muscle is stimulated by a series of electrical pulses delivered by an electrode to stimulate either the motor nerve or the muscle tissue itself.
Simultaneously, a computer-controlled servo motor in the testing apparatus oscillates the muscle while measuring the force generated by the stimulated muscle.
The following parameters are modulated by the experimenter to influence muscle force, work and power output: The time period over which the muscle receives electrical stimulation Stimulation pulse frequency: The number of stimulation pulses per stimulation duration Stimulation phase: The time delay between the onset of stimulation and muscle length change Strain amplitude: The number of shortening-lengthening periods per time period Strain frequency influences mechanical work output.
Note how stimulation phase influences both the shape and magnitude of force as well as the direction of the work loop. Net work is typically calculated either from instantaneous power muscle force x muscle velocity or from the area enclosed by the work loop on a force vs.
Skeletal muscle mechanics: questions, problems and possible solutions
Both methods are mathematically equivalent and highly accurate, however the 'area inside the loop' method despite its simplicity can be tedious to carry out for large data sets. Instantaneous power method[ edit ] Step 1 Obtain muscle velocity by numerical differentiation of muscle length data. Step 2 Obtain instantaneous muscle power by multiplying muscle force data by muscle velocity data for each time sample.