Force Production and Motor Unit

by Thad Wilson, PhD

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    So now let’s go through how force is produced. Force is produced in two different ways in skeletal muscle. The first way force is produced is how you would think about it, as you go through power strokes. As you contract a muscle, you’ll develop tension. Interestingly though, tension is developed be dependent upon the length of the muscle. So you get this kind of formation where you have a peak and two valleys. So at a certain length, your muscle will be the strongest or able to develop the most tension. And then, as you stretch it too far, it doesn’t develop as much tension, or if it is too contracted, it doesn’t develop as much tension. So there’s an optimal length for tension development. So this is the active process. When we put back in now a passive tension, and that is it’s less of an ability to be stretched. If you stretch it to a greater degree, it develops more tension just like a rubber band. If you pull on a rubber band, it starts to resist you as you get to a higher and higher length. That is the passive component of muscle tension. To determine the total muscle tension, you have to add these two together. And here, you have a peak in force at a given length associated with active force production and then you have a second peak associated with some active and some passive components. The other item that we need to consider is what is driving this process. It’s all based upon a nerve. We discussed alpha motor neurons earlier, now I’m going to group them together as an entity, as a motor unit. So that motor unit encompasses all the different fibers that it innervates, and one alpha motor neuron...

    About the Lecture

    The lecture Force Production and Motor Unit by Thad Wilson, PhD is from the course Musculoskeletal Physiology.

    Author of lecture Force Production and Motor Unit

     Thad Wilson, PhD

    Thad Wilson, PhD

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