{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,14]],"date-time":"2026-01-14T05:21:30Z","timestamp":1768368090017,"version":"3.49.0"},"reference-count":24,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2023,4,11]],"date-time":"2023-04-11T00:00:00Z","timestamp":1681171200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000049","name":"National Institute on Aging (National Institute of Health, USA)","doi-asserted-by":"publisher","award":["R01AG056999"],"award-info":[{"award-number":["R01AG056999"]}],"id":[{"id":"10.13039\/100000049","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Tomography"],"abstract":"<jats:p>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 (E\u03bb1) and radial expansion strains (E\u03bb2) 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\u03bb2 and Emax were significantly higher than E\u03bb1 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.<\/jats:p>","DOI":"10.3390\/tomography9020068","type":"journal-article","created":{"date-parts":[[2023,4,12]],"date-time":"2023-04-12T03:49:17Z","timestamp":1681271357000},"page":"840-856","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Strain and Strain Rate Tensor Mapping of Medial Gastrocnemius at Submaximal Isometric Contraction and Three Ankle Angles"],"prefix":"10.3390","volume":"9","author":[{"given":"Ryan","family":"Hernandez","sequence":"first","affiliation":[{"name":"Department of Physics, San Diego State University, San Diego, CA 92182, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Usha","family":"Sinha","sequence":"additional","affiliation":[{"name":"Department of Physics, San Diego State University, San Diego, CA 92182, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0426-1457","authenticated-orcid":false,"given":"Vadim","family":"Malis","sequence":"additional","affiliation":[{"name":"Muscle Imaging and Modeling Lab., Department of Radiology, University of California San Diego, San Diego, CA 92037, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Brandon","family":"Cunnane","sequence":"additional","affiliation":[{"name":"Department of Physics, San Diego State University, San Diego, CA 92182, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Edward","family":"Smitaman","sequence":"additional","affiliation":[{"name":"Department of Radiology, University of California San Diego, San Diego, CA 92182, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shantanu","family":"Sinha","sequence":"additional","affiliation":[{"name":"Muscle Imaging and Modeling Lab., Department of Radiology, University of California San Diego, San Diego, CA 92037, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,4,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1852","DOI":"10.1002\/mrm.25312","article-title":"Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: Potential index of lateral force transmission","volume":"73","author":"Sinha","year":"2014","journal-title":"Magn. 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