This type of muscle generally allows higher force production but a smaller range of motion.

Each muscle is composed of a number of fascicles grouped together by a sleeve of connective tissue, known as an epimysium.

If there are fascicles on both sides of the central tendon, the pennate muscle is called bipennate (Fig.

A better estimate is provided by the total area of the cross sections perpendicular to the muscle fibers (green lines in figure 1).

This measure is known as the physiological cross sectional area (PCSA), and is commonly calculated and defined by the following formula (an alternative definition is provided in the main article):[6][7][8] where ρ is the density of the muscle: PCSA increases with pennation angle, and with muscle length.

Namely, the maximum (tetanic) force of a muscle fiber simply depends on its thickness (cross-section area) and type.

[10] It was originally thought that the distance between aponeuroses did not change during the contraction of a pennate muscle,[5] thus requiring the fibers to rotate as they shorten.

However, recent work has shown this is false, and that the degree of fiber angle change varies under different loading conditions.