David Dongsuk Shin1, John A. Hodgson2, Sheng-Wei Chi3, Jiun-Shyan Chen3, V Reggie Edgerton2, Shantanu Sinha4
1Biomedical Engieering, University of California, Los Angeles, CA, USA; 2Physiological Science, University of California, Los Angeles, CA, USA; 3Civil & Environmental Engineering, University of California, Los Angeles, CA, USA; 4Radiology, University of California, San Diego, CA, USA
PC-MRI was used to estimate muscle fiber deformations in the medial gastrocnemius muscle undergoing passive and eccentric length changes. There was a progressive change in strain along fibers and along the proximo-distal axis of the muscle. Proximal fibers strained most near their origin and distal fibers strained most near their insertion. These data confirm predictions from FEM indicating that fibers will strain most in high stress regions of the muscle. The finding is contrary to the widely held view that muscle fibers strain uniformly along their length and suggests that intramuscular structural materials play an important role in force transmission.