Pennation angle

The pennation angle refers to the angle between the direction of muscle fibers and the overall force-generating axis of the muscle. Imagine fibers like blades of a fan; the angle they form with the central line of the fan affects how force is produced. A larger pennation angle allows more fibers to pack into a muscle, increasing strength, but slightly reduces the efficiency of force transmission along the muscle's length. It’s a key factor in how muscles grow stronger and adapt to different activities, balancing size and force output in the body.