The Lumbricals Are Not the Workhorse of Digital Extension and Do Not Relax Their Own Antagonist

Abstract

That the lumbrical muscles are the workhorse of digital extension and that they can relax their own antagonist have been time-honored principles. However, we believe this dogma is incorrect and an oversimplification. We base our assertion on anatomy, innervation, and the notion that muscle architecture is the most important determinant of muscle function. Wang and colleagues proposed the lumbrical to be a sophisticated tension monitoring device. We elaborate on their well-supported thesis, further proposing that the lumbricals also function as a constant tension spring within the closed loop composed of the digital flexors and the extensor mechanism.

Keywords: Interosseous muscle; intrinsic muscle; lumbrical muscle; skeletal muscle architecture.