Related Experiment Video
Updated: Aug 1, 2025

Author Spotlight: Integrating Mechanical and Biological Analysis in Tendinopathy Research
Published on: March 1, 2024
Strain and Strain Rate Tensor Mapping of Medial Gastrocnemius at Submaximal Isometric Contraction and Three Ankle
Ryan Hernandez1, Usha Sinha1, Vadim Malis2
1Department of Physics, San Diego State University, San Diego, CA 92182, USA.
Introduction:
The aim of this study is to analyze the muscle kinematics of the medial gastrocnemius (MG) during submaximal isometric contractions and to explore the relationship between deformation and force generated at plantarflexed (PF), neutral (N) and dorsiflexed (DF) ankle angles.
Method:
Strain and Strain Rate (SR) tensors were calculated from velocity-encoded magnetic resonance phase-contrast images in six young men acquired during 25% and 50% Maximum Voluntary Contraction (MVC). Strain and SR indices as well as force normalized values were statistically analyzed using two-way repeated measures ANOVA for differences with force level and ankle angle. An exploratory analysis of differences between absolute values of longitudinal compressive strain (Eλ1) and radial expansion strains (E) and maximum shear strain (Emax) based on paired t-test was also performed for each ankle angle.
Results:
Compressive strains/SRs were significantly lower at 25%MVC. Normalized strains/SR were significantly different between %MVC and ankle angles with lowest values for DF. Absolute values of E and Emax were significantly higher than E for DF suggesting higher deformation asymmetry and higher shear strain, respectively.
Conclusions:
In addition to the known optimum muscle fiber length, the study identified two potential new causes of increased force generation at dorsiflexion ankle angle, higher fiber cross-section deformation asymmetry and higher shear strains.
Related Concept Videos
Measurements of Strain
Three-Dimensional Analysis of Strain
Normal Strain under Axial Loading
Transformation of Plane Strain
Under plane strain conditions, typical for members where one dimension significantly exceeds the others, deformations and resultant strains are...

