Structural determinants of maximal O2 transport in muscles of exercising foxes

J. E P W Bicudo, K. E. Longworth, James H Jones, C. R. Taylor, H. Hoppeler

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The arctic blue fox (Alopex lagopus) has a specific maximal oxygen consumption (V̇(O2) max/Mb = 3.6 ml O2 · s-1 kg-1) that is approximately 1.6-fold greater than those of dogs and horses. The fox has one of the highest body mass specific skeletal muscle mitochondrial volumes (V(mt,m)/Mb = 44 cm3 · kg-1) among mammalian athletic species matching its higher V̇(O2) max/Mb. The structural components related to capillaries, such as specific capillary length density (J(c)/Mb = 348 km · kg-1) and specific capillary volume (V(c)/Mb = 4.8 ml · kg-1), are not greater in the fox than in the larger athletes. Because a greater specific muscle diffusing capacity for oxygen (DT(O2)/Mb) is not utilized by the fox to achieve a higher V̇(O2) max/Mb, a higher pressure difference for diffusion in the muscle capillaries is the alternative explanation for the fox's higher V̇(O2) max/Mb. This mechanism is suggested by the fox's higher arterial and mixed venous capillary P(O2) (120 mm Hg and 37 mm Hg, respectively) and its shorter mean muscle capillary transit time for blood (t̄c = 0.28 sec) compared to larger species.

Original languageEnglish (US)
Pages (from-to)243-251
Number of pages9
JournalRespiration Physiology
Issue number3
StatePublished - Mar 1996


  • Capillary, skeletal muscle
  • Exercise, maximal
  • Gas exchange, tissue
  • Mammals, fox (Alopex lagopus)
  • Morphometry, skeletal muscle
  • Muscle, skeletal, mitochondrial volume,
  • Oxygen, consumption, maximal

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine


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