{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,30]],"date-time":"2026-10-30T16:15:28Z","timestamp":1793376928813,"version":"4.5.0"},"reference-count":52,"publisher":"Public Library of Science (PLoS)","issue":"1","license":[{"start":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T00:00:00Z","timestamp":1768953600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003554","name":"Lundbeck Foundation","doi-asserted-by":"publisher","award":["R344-2020-254"],"award-info":[{"award-number":["R344-2020-254"]}],"id":[{"id":"10.13039\/501100003554","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003554","name":"Lundbeck Foundation","doi-asserted-by":"publisher","award":["R402-2022-1387"],"award-info":[{"award-number":["R402-2022-1387"]}],"id":[{"id":"10.13039\/501100003554","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Nordea fonden"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>The extent of inter-individual variability in response to heavy resistance exercise training (HReT), and the possible existence of non-responders, remains unclear. This study aimed to determine the degree of variability in response to prolonged HReT in healthy older men.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      We conducted a secondary analysis of an 8- and 16-week intervention involving thrice-weekly HReT (EX) or continuation of a sedentary lifestyle (SED). Fifty-eight healthy men (age 72\u2009\u00b1\u20095) were randomized to EX (n\u2009=\u200938) or SED (n\u2009=\u200920). Assessments were conducted at baseline, 8-weeks, and 16-weeks for five outcomes: maximal voluntary contraction strength (MVC), rate of force development (RFD), quadriceps cross-sectional area (qCSA), and type I and II myofibre cross-sectional area (fCSA). Inter-individual variability was assessed using the standard deviation of individual responses (SD\n                      <jats:sub>IR<\/jats:sub>\n                      ). Individual changes relative to a Typical Error were used to classify responders as Poor, Trivial, Robust, or Excellent.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>16 weeks of EX led to group-level increases in MVC (19\u2009\u00b1\u200914%), RFD (58\u2009\u00b1\u200980%), qCSA (3\u2009\u00b1\u20094%), and type II fCSA (14\u2009\u00b1\u200925%), with no changes in SED. Substantial inter-individual variability was observed. After 16 weeks, 82% of EX participants were classified as Robust or Excellent responders; only 5% were Poor responders. Training compliance and 1RM progression did not explain this variability. Lower baseline levels were linked to greater improvements but did not fully account for response differences.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec004\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>This study provides strong evidence of inter-individual variability in response to HReT among healthy older men. Given the rarity of true non-responders, our data support HReT as the universally recommended first-line strategy for enhancing muscle mass and strength.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1371\/journal.pone.0338775","type":"journal-article","created":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T18:24:16Z","timestamp":1769019856000},"page":"e0338775","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":8,"title":["Heavy resistance exercise training in older men: A responder and inter-individual variability analysis"],"prefix":"10.1371","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6579-5700","authenticated-orcid":true,"given":"Casper","family":"Soendenbroe","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jesper L.","family":"Andersen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mette F.","family":"Heisterberg","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Kjaer","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2017-4580","authenticated-orcid":true,"given":"Abigail L.","family":"Mackey","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2026,1,21]]},"reference":[{"issue":"18","key":"pone.0338775.ref001","doi-asserted-by":"crossref","first-page":"1211","DOI":"10.1136\/bjsports-2023-106807","article-title":"Resistance training prescription for muscle strength and hypertrophy in healthy adults: a systematic review and Bayesian network meta-analysis","volume":"57","author":"BS Currier","year":"2023","journal-title":"Br J Sports Med"},{"issue":"1","key":"pone.0338775.ref002","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1007\/s004210000248","article-title":"Neuromuscular adaptation during prolonged strength training, detraining and re-strength-training in middle-aged and elderly people","volume":"83","author":"K H\u00e4kkinen","year":"2000","journal-title":"Eur J Appl Physiol"},{"key":"pone.0338775.ref003","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1016\/j.exger.2017.03.014","article-title":"Improved skeletal muscle mass and strength after heavy strength training in very old individuals","volume":"92","author":"RL Bechsh\u00f8ft","year":"2017","journal-title":"Exp Gerontol"},{"issue":"5","key":"pone.0338775.ref004","doi-asserted-by":"crossref","first-page":"6418","DOI":"10.1096\/fj.202000196R","article-title":"Preserved capacity for satellite cell proliferation, regeneration, and hypertrophy in the skeletal muscle of healthy elderly men","volume":"34","author":"A Karlsen","year":"2020","journal-title":"FASEB J"},{"issue":"1","key":"pone.0338775.ref005","doi-asserted-by":"crossref","DOI":"10.1152\/ajpcell.00365.2021","article-title":"Human skeletal muscle acetylcholine receptor gene expression in elderly males performing heavy resistance exercise","volume":"323","author":"C Soendenbroe","year":"2022","journal-title":"Am J Physiol Cell Physiol"},{"issue":"6","key":"pone.0338775.ref006","first-page":"964","article-title":"Variability in muscle size and strength gain after unilateral resistance training","volume":"37","author":"MJ Hubal","year":"2005","journal-title":"Med Sci Sports Exerc"},{"issue":"5","key":"pone.0338775.ref007","doi-asserted-by":"crossref","first-page":"400","DOI":"10.1016\/j.jamda.2015.01.071","article-title":"There Are No Nonresponders to Resistance-Type Exercise Training in Older Men and Women","volume":"16","author":"TA Churchward-Venne","year":"2015","journal-title":"J Am Med Dir Assoc"},{"issue":"7","key":"pone.0338775.ref008","doi-asserted-by":"crossref","first-page":"966","DOI":"10.1002\/sim.6739","article-title":"Mastering variation: variance components and personalised medicine","volume":"35","author":"S Senn","year":"2016","journal-title":"Stat Med"},{"issue":"12","key":"pone.0338775.ref009","doi-asserted-by":"crossref","first-page":"1450","DOI":"10.1152\/japplphysiol.00714.2014","article-title":"Individual response to exercise training - 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