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Updated: Oct 5, 2025

Cantilever Bending of Murine Femoral Necks
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Can we just forget about pennation angle?

Richard L Lieber1

  • 1Shirley Ryan AbilityLab, Chicago, IL, USA; Departments of Physical Medicine and Rehabilitation and Biomedical Engineering, Northwestern University, Chicago, IL, USA; Hines VA Medical Center, Maywood, IL, USA.

Journal of Biomechanics
|January 25, 2022
PubMed
Summary
This summary is machine-generated.

Muscle pennation, the angle of muscle fibers, may not significantly impact force generation. This angle likely serves as a packing strategy for short fibers within a limited muscle volume.

Keywords:
Fiber lengthFiber typeMulitpennateMuscle architecturePhysiologicalRoss-sectional areaUnipennate

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Area of Science:

  • Biomechanics
  • Skeletal Muscle Anatomy

Background:

  • Muscle fiber orientation relative to force generation has been studied for centuries.
  • The pennation angle is a key feature in skeletal muscle biomechanics literature, often linked to force production.

Purpose of the Study:

  • To re-evaluate the functional significance of muscle pennation.
  • To propose an alternative perspective on pennation as a fiber packing strategy.

Main Methods:

  • Review of anatomical studies and biomechanical literature.
  • Analysis of the relationship between pennation angle and muscle function.

Main Results:

  • The study suggests that muscle pennation angle has minimal to no functional significance for force generation.
  • Pennation is proposed to be primarily a mechanism for efficiently packing short muscle fibers into a confined space.

Conclusions:

  • The observed pennation angle, despite being measurable and dynamic during contraction, may not be functionally relevant for muscle force output.
  • A paradigm shift is suggested, viewing pennation as a structural adaptation for volume optimization rather than a primary determinant of force generation.