{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T18:12:47Z","timestamp":1789150367276,"version":"build-2803163510"},"reference-count":45,"publisher":"Public Library of Science (PLoS)","issue":"9","license":[{"start":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T00:00:00Z","timestamp":1789084800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>This study examined within-player associations between GPS-derived external training load variables and heart rate-based internal training load during in-season training in elite youth soccer players. A secondary aim was to identify which intensity-based external load variables are independently associated with heart rate (HR) exertion per minute.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Eleven under-17 male soccer players were monitored across a nine-week in-season period. 266 player-session observations were included. External training load was assessed using GPS units with integrated inertial sensors, including total distance covered, high-speed running distance, explosive efforts, player load, and their time-normalized derivatives. Internal training load was quantified using heart rate exertion derived from individualized HR zones. Within-player associations were examined using repeated-measures correlations. A linear mixed-effects model was used to examine predictors of heart rate exertion per minute.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      HR exertion showed nearly perfect within-player associations with total distance covered (r\u2009=\u20090.921, p\u2009&lt;\u20090.001) and PlayerLoad\n                      <jats:sup>TM<\/jats:sup>\n                      (r\u2009=\u20090.924, p\u2009&lt;\u20090.001), while large associations were observed for high-speed running distance (r\u2009=\u20090.662, p\u2009&lt;\u20090.001) and explosive efforts (r\u2009=\u20090.621, p\u2009&lt;\u20090.001). Intensity-based variables, including total distance covered per minute and explosive efforts per minute, were significant positive predictors of HR exertion\u00b7min\u2009\n                      <jats:sup>\u2212<\/jats:sup>\n                      \u2009\u00b9.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec004\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>\n                      In elite under-17 youth soccer training, cumulative HR exertion primarily reflects accumulated external training volume, whereas HR exertion\u00b7min\u2009\n                      <jats:sup>\u2212<\/jats:sup>\n                      \u2009\u00b9 is more closely related to locomotor and explosive action intensity. These findings highlight the need to interpret cumulative and intensity-based internal training load metrics separately in within-player training monitoring.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1371\/journal.pone.0357176","type":"journal-article","created":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T17:59:28Z","timestamp":1789149568000},"page":"e0357176","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["Within-player associations between GPS-derived external training load and heart rate-based internal training load in elite youth male soccer training"],"prefix":"10.1371","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8365-4848","authenticated-orcid":true,"given":"Kriszti\u00e1n","family":"Havanecz","sequence":"first","affiliation":[{"name":"Training Theory and Methodology Research Center, Hungarian University of Sports 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