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Short communication: pennation angle variability in human muscle.

Benjamin W Infantolino1, John H Challis

  • 1Biomechanics Laboratory, Pennsylvania State University, State College, PA.

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Summary

Muscle fascicle arrangement creates significant pennation angle variations within the first dorsal interosseous (FDI) muscle. These findings suggest a single angle may not accurately represent whole muscle pennation, impacting biomechanical models.

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Area of Science:

  • Anatomy
  • Biomechanics
  • Medical Imaging

Background:

  • Muscle fascicle arrangement influences in vivo muscle function.
  • The complex structure of whole muscles raises questions about pennation angle uniformity.

Purpose of the Study:

  • To investigate and describe pennation angle variability within the first dorsal interosseous (FDI) muscle.
  • To determine if fascicle arrangement leads to variations in pennation angle throughout the muscle.

Main Methods:

  • Utilized high-resolution 14.1 tesla magnetic resonance imaging (MRI) on two cadaveric FDI muscles.
  • Muscles were sectioned, and pennation angles were measured across medial-lateral and anterior-posterior planes in representative locations within each slice.

Main Results:

  • Observed significant and non-uniform variations in pennation angles throughout the FDI muscle.
  • Pennation angles ranged from 3.2° to 22.6° along the medial-lateral axis and 3.1° to 24.5° along the anterior-posterior axis in one specimen.
  • The distribution of pennation angles was non-normal, indicating complex fascicle arrangements.

Conclusions:

  • A single, uniform pennation angle may not accurately represent the complex fascicle arrangement in whole muscles like the FDI.
  • The observed variability has implications for understanding muscle function and developing accurate biomechanical models.