What is pennation angles?

Pennation angle refers to the angle between muscle fibers and the tendon that attaches the muscle to bone. It is determined by the orientation of the muscle fibers within the muscle. Muscles with a high pennation angle have fibers that are oriented at a steep angle to the tendon, while muscles with a low pennation angle have fibers that are oriented more parallel to the tendon. Pennation angle is an important factor in understanding the force-generating capacity and velocity of muscle contraction. Muscles with a high pennation angle tend to generate greater forces but at a slower velocity, while muscles with a low pennation angle tend to generate lower forces but at a higher velocity. The pennation angle varies across different muscles in the body, with some muscles having a more parallel fiber arrangement and others having a more oblique arrangement.