Specific tension of human plantarflexors and dorsiflexors.
Fukunaga, T., R. R. Roy, F. G. Shellock, J. A. Hodgson, and V. R.
Edgerton.
Department of Physiological Science, Brain Research Institute and
Department of Radiological Sciences, University of California, Los
Angeles Los Angeles, CA 90024 and Department of Sports Sciences,
University of Tokyo, 153, 3-8-1 Komaba Meguro Tokyo, Japan
APStracts 2:0382A, 1995.
Reported specific tension measurements for human skeletal muscle vary
widely. This variability could be due, at least in part, to the
determination of the physiological cross-sectional area (PCSA) of the
muscles. In the present study, serial magnetic resonance images were
taken every 10 mm along the lower leg of 8 male subjects to calculate
the volume and subsequently the PCSAs of the individual muscles
producing plantarflexor and dorsiflexor torques. Maximum
plantarflexor and dorsiflexor voluntary isometric torques were
determined at ankle joint angles of 90, 100, 110 and 120o. Peak
tendon force estimated from torque and moment arm measurements was
more than 4-fold higher in the plantarflexors (3623 +/- 136 N) than
the dorsiflexors (832 +/- 19 N). PCSAs were 8- and 3-fold higher than
the anatomical CSA at the level of maximum girth of the calf for the
plantarflexor and dorsiflexor groups, respectively. Mean muscle
volume and PCSA were 4.6 and 12 times larger in the plantarflexors
compared to the dorsiflexors, respectively. The PCSA of both
plantarflexors (r=0.92) and dorsiflexors (r=0.80) were highly
correlated with the tendon tension of the respective muscle groups.
The maximum specific tension was more than 2-fold higher in
dorsiflexors than plantarflexors. These data suggest that factors
other than PCSA contribute to the force output potential of ankle
plantarflexors and dorsiflexors in the human.
Received 27 December 1994; accepted in final form 14 August 1995.
APS Manuscript Number A1346-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.