The isometric functional capacity of muscles that cross the elbow

Wendy M. Murray*, Thomas S. Buchanan, Scott L. Delp

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

222 Scopus citations

Abstract

We hypothesized that muscles crossing the elbow have fundamental differences in their capacity for excursion, force generation, and moment generation due to differences in their architecture, moment arm, and the combination of their architecture and moment arm. Muscle fascicle length, sarcomere length, pennation angle, mass, and tendon displacement with elbow flexion were measured for the major elbow muscles in 10 upper extremity specimens. Optimal fascicle length, physiological cross-sectional area (PCSA), moment arm, operating range on the force-length curve, and moment-generating capacity were estimated from these data. Brachioradialis and pronator teres had the longest (17.7cm) and shortest (5.5cm) fascicles, respectively. Triceps brachii (combined heads) and brachioradialis had the greatest (14.9cm2) and smallest (1.2cm2) PCSAs, respectively. Despite a comparable fascicle length, long head of biceps brachii operates over a broader range of the force-length curve (length change=56% of optimal length, 12.8cm) than the long head of triceps brachii (length change=28% of optimal length, 12.7cm) because of its larger moment arm (4.7cm vs. 2.3cm). Although brachioradialis has a small PCSA, it has a relatively large moment-generating capacity (6.8cm3) due to its large moment arm (average peak=7.7cm). These results emphasize the need to consider the interplay of architecture and moment arm when evaluating the functional capabilities of a muscle. Copyright (C) 2000 Elsevier Science Ltd.

Original languageEnglish (US)
Pages (from-to)943-952
Number of pages10
JournalJournal of Biomechanics
Volume33
Issue number8
DOIs
StatePublished - Aug 1 2000

Keywords

  • Elbow
  • Moment arms
  • Muscle architecture

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine
  • Biomedical Engineering
  • Rehabilitation

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