Flat muscle with fibres arranged around one or more central tendons like the barbs of a feather. Pennate muscles shorten only to a limited extent, but they can produce very powerful actions. Pennate muscle may be unipennate, when the fibres insert onto only one side of a tendon (e.g. extensor digitorum longum); bipennate, when fibres insert onto opposite sides of a tendon so that the muscle resembles a feather (e.g. rectus femoris); or multipennate, when fibres converge onto several tendons, giving a herringbone appearance (e.g. deltoid muscle). Compare fusiform muscle.
Subjects: Sports and Exercise Medicine.