Super interesting! Thanks for sharing. Odd question but when considering the work of a single muscle fiber in a pennated muscle, it seems like it would be less than a longitudinal muscle fiber, thay was the same length and size. So each muscle fiber would have the same force output but in the pennated muscle, because it is at an angle, some of the force would be applied laterally to the tendon (if we broke it down to vectors) and some of it would be applied down the length of the tendon, and that latter force vector would be the component of the force that was actually doing work. While the force applied laterally to the tendon would be counteracted by another muscle fiber on the other side. Conversely, 100% of longitudinal muscle fibers force would be down the length of the tendon. So say we have 2 muscle fibers that are each able to apply 1N of force. In one case, they are parallel in a longitudinal muscle. In another case, they are at a 90 degree angle to each other, attached to the same point on a tendon, on either side, so that each is 45 degrees away from the tendon. In the first case, the two fibers contracting produce a force of 2N at the end of the tendon. In the second case, the two muscle fibers are somewhat pulling against each other, so the lateral forces on the tendon “cancel out” but the forces inline with the tendon add together and, using Pythagoras, would result in a force at the end of the tendon of 2root2. But even though that individual pair can pull less in pennated muscle, the advantage of pennated muscle is packing so many more muscle fibers in a space that the muscle is stronger overall. Is this all on the right track?
Been watching your videos and I love how you explain concepts. Hardly see anyone explain concepts like this ones. Any chance you could do a video on muscle architectural gear ratio?
Hi Dan, thanks for the feedback! This concept is used to understand the design of skeletal muscle and how that design influences its function. Besides giving us a better grasp of how muscles work, the concept of pennation angle can be applied when doing research and comparing the relative pennation angles from one muscle to another, or of the same muscle between individuals. By measuring the pennation angle of a muscle, along with the length and weight of the fibers, a researcher can estimate how many fibers are contained within a muscle, and therefore how much force it would be capable of producing. All research like I am describing is essentially conducted so we can learn more about the structure and function of various muscles. I hope that helps, and thanks for watching!
One more question: does pennation angle tend to change depending on how contracted a muscle is? Like, in a pennated muscle i’d imagine the muscle fibers are more inline with the longitudinal axis when the muscle is stretched and become closer to perpendicular with the longitudinal axis when the muscle is contracted
Would type 1 muscle fibers have more of a linear shape like the hamstrings and the vasti (quads) have type 2 muscle fibers shape being more pennate? Just trying to apply the concept 🙂
Great question, Matt! All muscles are a blend of fiber types, so there is no such thing as a muscle that is made up of 100% of one type of fiber. Different muscles will have different proportions of fiber types depending on the needs of that muscle, but all muscles have a blend. Although it might seem like a pennated muscle would have more type II fibers than a longitudinal muscle because the priority is force production, that isn't necessarily the case. Consider that a longitudinal muscle has more length to take up during contraction, so it needs to contract faster than a pennate muscle would to cover the same distance. The shorter the fibers, the slower they can contract because they don't have as much distance to cover within the same amount of time. Since type II fibers have a faster speed of contraction, that is an argument for why longitudinal muscles might benefit from more type II fibers. Really what I am trying to say is that we can't make an assumption about the proportions of fiber types in a muscle based strictly on the muscle's architecture, because there are so many different factors involved. I hope this answers your question, and thanks for watching!
Yes and thank you very much this helps a lot. I am studying kinesiology and the video helps my understanding of pennation angle. I will be watching your other videos as well thanks again.
this is one of the best explanations I've heard on this topic and in a really easy way to understand
Thanks so much, that means a lot to me!
Super interesting! Thanks for sharing.
Odd question but when considering the work of a single muscle fiber in a pennated muscle, it seems like it would be less than a longitudinal muscle fiber, thay was the same length and size. So each muscle fiber would have the same force output but in the pennated muscle, because it is at an angle, some of the force would be applied laterally to the tendon (if we broke it down to vectors) and some of it would be applied down the length of the tendon, and that latter force vector would be the component of the force that was actually doing work. While the force applied laterally to the tendon would be counteracted by another muscle fiber on the other side. Conversely, 100% of longitudinal muscle fibers force would be down the length of the tendon.
So say we have 2 muscle fibers that are each able to apply 1N of force. In one case, they are parallel in a longitudinal muscle. In another case, they are at a 90 degree angle to each other, attached to the same point on a tendon, on either side, so that each is 45 degrees away from the tendon. In the first case, the two fibers contracting produce a force of 2N at the end of the tendon. In the second case, the two muscle fibers are somewhat pulling against each other, so the lateral forces on the tendon “cancel out” but the forces inline with the tendon add together and, using Pythagoras, would result in a force at the end of the tendon of 2root2.
But even though that individual pair can pull less in pennated muscle, the advantage of pennated muscle is packing so many more muscle fibers in a space that the muscle is stronger overall.
Is this all on the right track?
Been watching your videos and I love how you explain concepts. Hardly see anyone explain concepts like this ones.
Any chance you could do a video on muscle architectural gear ratio?
Thanks so much for the topic idea! I'll add it to my list, and maybe I will make a video on the topic in the future. Thanks for the suggestion!
Great video Veronica, explained really well and I understood after watching first time. How would this information be useful in practice? Thanks
Hi Dan, thanks for the feedback! This concept is used to understand the design of skeletal muscle and how that design influences its function. Besides giving us a better grasp of how muscles work, the concept of pennation angle can be applied when doing research and comparing the relative pennation angles from one muscle to another, or of the same muscle between individuals. By measuring the pennation angle of a muscle, along with the length and weight of the fibers, a researcher can estimate how many fibers are contained within a muscle, and therefore how much force it would be capable of producing. All research like I am describing is essentially conducted so we can learn more about the structure and function of various muscles. I hope that helps, and thanks for watching!
One more question: does pennation angle tend to change depending on how contracted a muscle is? Like, in a pennated muscle i’d imagine the muscle fibers are more inline with the longitudinal axis when the muscle is stretched and become closer to perpendicular with the longitudinal axis when the muscle is contracted
Pennation angle something many coaches do not take into consideration.
Very important topic I say.
Thanks, Kenan!
Would type 1 muscle fibers have more of a linear shape like the hamstrings and the vasti (quads) have type 2 muscle fibers shape being more pennate? Just trying to apply the concept 🙂
Great question, Matt! All muscles are a blend of fiber types, so there is no such thing as a muscle that is made up of 100% of one type of fiber. Different muscles will have different proportions of fiber types depending on the needs of that muscle, but all muscles have a blend. Although it might seem like a pennated muscle would have more type II fibers than a longitudinal muscle because the priority is force production, that isn't necessarily the case. Consider that a longitudinal muscle has more length to take up during contraction, so it needs to contract faster than a pennate muscle would to cover the same distance. The shorter the fibers, the slower they can contract because they don't have as much distance to cover within the same amount of time. Since type II fibers have a faster speed of contraction, that is an argument for why longitudinal muscles might benefit from more type II fibers. Really what I am trying to say is that we can't make an assumption about the proportions of fiber types in a muscle based strictly on the muscle's architecture, because there are so many different factors involved. I hope this answers your question, and thanks for watching!
Yes and thank you very much this helps a lot. I am studying kinesiology and the video helps my understanding of pennation angle. I will be watching your other videos as well thanks again.
Sounds great, and happy studying!