Dimensions of forelimb muscles in orangutans and chimpanzees

Motoharu Oishi, Naomichi Ogihara, Hideki Endo, Nobutsune Ichihara, Masao Asari

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)


Eight forelimbs of three orangutans and four chimpanzees were dissected and the muscle mass, fascicle length and physiological cross-sectional area (PCSA) of all forelimb muscles were systematically recorded to explore possible interspecies variation in muscle dimensions. Muscle mass and PCSA were divided by the total mass and total PCSA of the entire forelimb muscles for normalization. The results indicate that the mass and PCSA ratios of the monoarticular elbow flexors (M. brachialis and M. brachioradialis) are significantly larger in orangutans. In contrast, the mass ratios of the biarticular muscles in the upper arm (the short head of M. biceps brachii and the long head of M. triceps brachii) are significantly larger in chimpanzees. For the rotator cuff muscles, the force-generating capacity of M. subscapularis is significantly larger in orangutans, whereas the opposite rotator cuff muscle, M. infraspinatus, is larger in chimpanzees. These differences in forelimb muscle dimensions of the two species may reflect functional specialization for their different positional and locomotor behaviors.

Original languageEnglish
Pages (from-to)373-382
Number of pages10
JournalJournal of Anatomy
Issue number4
Publication statusPublished - 2009 Oct


  • Locomotion
  • Pan
  • Physiological cross-sectional area
  • Pongo
  • Positional behavior

ASJC Scopus subject areas

  • Anatomy
  • Histology
  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Developmental Biology
  • Cell Biology


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