Isometric tension and myofilamental cross-sectional area in striated muscle

¹ National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland; and Department of Neurological Surgery, College of Physicians and Surgeons, Columbia University. New York City

Isometric tension in tetanically stimulated calf muscles was examined in vivo in 3 rabbits and 18 cats. In two cats the gastrocnemius and soleus muscles were studied separately. After determination of the isometric tension the muscles were dissected and their water content, total N content, and protein composition were analyzed. On this basis it was possible to calculate that part of the cross-sectional area of the muscle fibers which consisted of myofilaments. The recorded maximum isometric tension was related to the myofilamental cross-sectional area. Under the given experimental conditions, the calf muscles developed a tension of 108 ± 5 g/mm² cross-sectional area. Higher values resulted from tests of individual calf muscles than from combined muscles.