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Force Lab.docx - 12pm-2pm Force Production Lab Introduction...

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9-8-17 12pm-2pm Force Production Lab Introduction Tension is created in the muscle when there is a resistance acting on the muscle. The more tension that is in the muscle, the more motor units that are in the muscle that gets recruited. When a force is acting on a muscle then the muscle has to recruit motor units to oppose the force. The force that the motor units produce is dependent on 3 factors: Length of muscle, the angle of pull, and velocity of shortening. All of these three factors can cause a difference in force either by increasing or decreasing force. The first factor that can influence force is the length of the muscle. The reason this is significant is due to the fact that if the muscle is at its optimal length then there will be more sites for actin and myosin to interact with each other and if this happens it will increase the tension of the muscle causing more motor units to get activated. If the muscle is to short or to long then it will have less binding sites. Muscle length is also important for the formation of cross-bridges. The muscle size can affect this because it affects the diffusion capacity of calcium and if the muscle has slowed calcium diffusion then fewer cross bridges will be formed. The second factor that can affect force production is the angle of pull. The angle between the muscle, bone, and weight can alter the amount of force that is acting on that muscle. A good example of this is the muscles in the arm. If these muscles are anywhere above or under 90
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degrees then there is, to some extent, wasted pulling power. When the arm angle is at 90 degrees the muscle is applying all of its force directly to the bone making the force being completely used. Any angle other than that there is wasted force, but this force is still needed. It helps with joint integrity. The third factor is the velocity of the shortening of the muscle. As the velocity increased the force of the muscle is decreased. This is because as the velocity increases there is less time for the muscle to form cross-bridges and therefore decreasing the overall force produced by the muscle, but the force is not the only component of strength. Image taken from: http://4.bp.blogspot.com/-P_UuFJat-Oc/VV- ZSsVgVfI/AAAAAAAABdk/N5u0P0Gfidc/s1600/FV%2Bcurve_web.jpg Fig.1 In this figure you can see the relationship between the velocity of shortening compared to the relative force.
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There are three components of strength and these three components are the force, work, and power. Each one of these components is needed to calculate the others and because of this, they are directly related to each other. Force is found based on the 3 components stated before.
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