{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T12:01:54Z","timestamp":1781784114563,"version":"3.54.5"},"reference-count":27,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2022,3,26]],"date-time":"2022-03-26T00:00:00Z","timestamp":1648252800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The assessment of the force\u2013length relationship under mechanical loading is widely used to evaluate the mechanical properties of tendons and to gain information about their adaptation, function, and injury. This study aimed to provide a time-efficient ultrasound method for assessing Achilles tendon mechanical properties. On two days, eleven healthy young non-active adults performed eight maximal voluntary isometric ankle plantarflexion contractions on a dynamometer with simultaneous ultrasonographic recording. Maximal tendon elongation was assessed by digitizing ultrasound images at rest and at maximal tendon force. Achilles tendon stiffness index was calculated from the ratio of tendon force-to-strain. No within- and between-day differences were detected between the proposed method and manual frame by frame tracking in Achilles tendon maximal force, maximal elongation, maximal strain, and stiffness index. The overall coefficient of variation between trials ranged from 3.4% to 10.3% and average difference in tendon tracking between methods was less than 0.6% strain. Furthermore, an additional assessment demonstrated significant differences between elite athletes, healthy young, and older adults in Achilles tendon force and stiffness index. Hence, the analysis has the potential to reliably and accurately monitor changes in Achilles tendon mechanical properties due to aging and altered mechanical loading in a time-efficient manner.<\/jats:p>","DOI":"10.3390\/s22072549","type":"journal-article","created":{"date-parts":[[2022,3,27]],"date-time":"2022-03-27T21:31:25Z","timestamp":1648416685000},"page":"2549","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Reliability and Accuracy of a Time-Efficient Method for the Assessment of Achilles Tendon Mechanical Properties by Ultrasonography"],"prefix":"10.3390","volume":"22","author":[{"given":"Steve","family":"Hunter","sequence":"first","affiliation":[{"name":"Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5268-2478","authenticated-orcid":false,"given":"Julian","family":"Werth","sequence":"additional","affiliation":[{"name":"Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Darren","family":"James","sequence":"additional","affiliation":[{"name":"Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2902-4255","authenticated-orcid":false,"given":"Yiannis","family":"Lambrianides","sequence":"additional","affiliation":[{"name":"Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kenton","family":"Smith","sequence":"additional","affiliation":[{"name":"Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1839-6643","authenticated-orcid":false,"given":"Kiros","family":"Karamanidis","sequence":"additional","affiliation":[{"name":"Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7241-1533","authenticated-orcid":false,"given":"Gaspar","family":"Epro","sequence":"additional","affiliation":[{"name":"Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,3,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"649","DOI":"10.1111\/j.1469-7793.2001.0649c.xd","article-title":"Effects of different duration isometric contractions on tendon elasticity in human quadriceps muscles","volume":"536","author":"Kubo","year":"2001","journal-title":"J. Physiol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2743","DOI":"10.1242\/jeb.003814","article-title":"Adaptational responses of the human Achilles tendon by modulation of the applied cyclic strain magnitude","volume":"210","author":"Arampatzis","year":"2007","journal-title":"J. Exp. Biol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"670","DOI":"10.1152\/japplphysiol.00259.2009","article-title":"Tendinopathy alters mechanical and material properties of the Achilles tendon","volume":"108","author":"Arya","year":"2010","journal-title":"J. Appl. Physiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"4715","DOI":"10.1242\/jeb.01950","article-title":"In vivo mechanical properties of the human Achilles tendon during one-legged hopping","volume":"208","author":"Lichtwark","year":"2005","journal-title":"J. Exp. Biol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"406","DOI":"10.1016\/j.jbiomech.2004.12.017","article-title":"Mechanical and morphological properties of human quadriceps femoris and triceps surae muscle-tendon unit in relation to aging and running","volume":"39","author":"Karamanidis","year":"2006","journal-title":"J. Biomech."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1016\/j.jelekin.2006.09.008","article-title":"Mechanical and morphological properties of the triceps surae muscle-tendon unit in old and young adults and their interaction with a submaximal fatiguing contraction","volume":"18","author":"Mademli","year":"2008","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1675","DOI":"10.3389\/fphys.2020.607544","article-title":"Monitoring Muscle-Tendon Adaptation over Several Years of Athletic Training and Competition in Elite Track and Field Jumpers","volume":"11","author":"Karamanidis","year":"2020","journal-title":"Front. Physiol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"3073","DOI":"10.1016\/j.jbiomech.2010.08.014","article-title":"Plasticity of human Achilles tendon mechanical and morphological properties in response to cyclic strain","volume":"43","author":"Arampatzis","year":"2010","journal-title":"J. Biomech."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"772","DOI":"10.1016\/j.clinbiomech.2011.02.011","article-title":"Mechanical properties of the human Achilles tendon, in vivo","volume":"26","author":"Kongsgaard","year":"2011","journal-title":"Clin. Biomech."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1111\/j.1469-7793.2001.0277j.x","article-title":"Load-displacement properties of the human triceps surae aponeurosis in vivo","volume":"531","author":"Magnusson","year":"2001","journal-title":"J. Physiol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1123\/jab.24.1.75","article-title":"An algorithm for automated analysis of ultrasound images to measure tendon excursion in vivo","volume":"24","author":"Lee","year":"2008","journal-title":"J. Appl. Biomech."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1019","DOI":"10.1016\/S0021-9290(02)00047-7","article-title":"Tensile properties of in vivo human tendinous tissue","volume":"35","author":"Maganaris","year":"2002","journal-title":"J. Biomech."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"665","DOI":"10.1152\/japplphysiol.00624.2004","article-title":"Elastic properties of human Achilles tendon are correlated to muscle strength","volume":"99","author":"Muraoka","year":"2005","journal-title":"J. Appl. Physiol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"238","DOI":"10.1177\/0269215510382600","article-title":"The effect of eccentric and concentric calf muscle training on Achilles tendon stiffness","volume":"25","author":"Morrissey","year":"2011","journal-title":"Clin. Rehabil."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1689","DOI":"10.1016\/j.ultrasmedbio.2016.02.019","article-title":"Use of a Lucas-Kanade-based template tracking algorithm to examine in vivo tendon excursion during voluntary contraction using ultrasonography","volume":"42","author":"Karamanidis","year":"2016","journal-title":"Ultrasound Med. Biol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"517","DOI":"10.1111\/cpf.12472","article-title":"Loading rate and contraction duration effects on in vivo human Achilles tendon mechanical properties","volume":"38","author":"McCrum","year":"2018","journal-title":"Clin. Physiol. Funct. Imaging"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"S39","DOI":"10.1098\/rsbl.2003.0004","article-title":"Tendon conditioning: Artefact or property?","volume":"270","author":"Maganaris","year":"2003","journal-title":"Proc. Biol. Sci."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"3266","DOI":"10.1242\/jeb.018812","article-title":"Running biomechanics: Shorter heels, better economy","volume":"211","author":"Scholz","year":"2008","journal-title":"J. Exp. Biol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1671","DOI":"10.1152\/jappl.2001.90.5.1671","article-title":"Mechanical properties of tendon and aponeurosis of human gastrocnemius muscle in vivo","volume":"90","author":"Muramatsu","year":"2001","journal-title":"J. Appl. Physiol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"419","DOI":"10.1016\/0021-9290(83)90074-X","article-title":"Tendon excursion and moment arm of index finger muscles","volume":"16","author":"An","year":"1983","journal-title":"J. Biomech."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"363","DOI":"10.1007\/s004210000247","article-title":"In vivo measurement-based estimations of the human Achilles tendon moment arm","volume":"83","author":"Maganaris","year":"2000","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_22","unstructured":"Portney, L.G. (2020). Foundations of Clinical Research: Applications to Evidence-Based Practice, FA Davis. [4th ed.]."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/j.jcm.2016.02.012","article-title":"A Guideline of Selecting and Reporting Intraclass Correlation Coefficients for Reliability Research","volume":"15","author":"Koo","year":"2016","journal-title":"J. Chiropr. Med."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"217","DOI":"10.2165\/00007256-199826040-00002","article-title":"Statistical methods for assessing measurement error (reliability) in variables relevant to sports medicine","volume":"26","author":"Atkinson","year":"1998","journal-title":"Sports Med."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1016\/j.gaitpost.2009.08.249","article-title":"Reproducibility of fascicle length and pennation angle of gastrocnemius medialis in human gait in vivo","volume":"31","author":"Aggeloussis","year":"2010","journal-title":"Gait Posture"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"833","DOI":"10.1016\/j.jbiomech.2004.04.031","article-title":"Strain and elongation of the human gastrocnemius tendon and aponeurosis during maximal plantarflexion effort","volume":"38","author":"Arampatzis","year":"2005","journal-title":"J. Biomech."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"413","DOI":"10.1016\/j.jelekin.2005.10.001","article-title":"In vivo motion transmission in the inactive gastrocnemius medialis muscle-tendon unit during ankle and knee joint rotation","volume":"16","author":"Arampatzis","year":"2006","journal-title":"J. Electromyogr. Kinesiol."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/7\/2549\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:43:58Z","timestamp":1760136238000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/7\/2549"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,3,26]]},"references-count":27,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2022,4]]}},"alternative-id":["s22072549"],"URL":"https:\/\/doi.org\/10.3390\/s22072549","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,3,26]]}}}