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First published online August 18, 2005
Journal of Experimental Biology 208, 3275-3279 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01763

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Sarcomere length measurement permits high resolution normalization of muscle fiber length in architectural studies

Amanda Felder, Samuel R. Ward and Richard L. Lieber^*

Departments of Orthopaedic Surgery and Bioengineering, University of California and Department of Veterans Affairs Medical Centers, San Diego, CA 92161, USA

View larger version (84K): [in a new window]   Fig. 1. (A) Photograph of a disarticulated and skinned mouse hindlimb secured to cork for fixation and architectural analysis. Bones are pinned with 30 gauge needles and the foot is secured to a cork footplate that aligns the tarsal and metatarsal bones. In this example, we attempted to fix the limb in 90° of knee flexion and 90° of ankle flexion. TA, tibialis anterior. (B) Lateral radiograph of hindlimb shown in A. Ankle and knee joint angles were as defined as in Materials and methods (shown as dotted lines) and were measured as 89.4° (knee) and 92.4° (ankle).

View larger version (24K): [in a new window]   Fig. 2. Relationship between fiber length and joint angle measured radiographically without (A–C) and with (D–F) sarcomere length normalization. (A) Tibialis anterior (TA) raw fiber length vs ankle angle, (B) Extensor digitorum longus (EDL) raw fiber length vs ankle angle, (C) Soleus raw fiber length vs ankle angle, (D) TA normalized fiber length vs ankle angle, (E) EDL normalized fiber length vs ankle angle, (F) Soleus normalized fiber length vs ankle angle. Regression relationships in A, B and C were statistically significant while those in D, E and F were not. See text for details.

View larger version (17K): [in a new window]   Fig. 3. Relationship between percent fiber length difference detected between groups and statistical power for Extensor digitorum longus (EDL; broken line), soleus (solid line) and Tibialis anterior (TA; dotted line) muscles. These calculations demonstrate that sarcomere length normalization easily permits resolution of fiber length differences of 15%.