{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T10:11:38Z","timestamp":1789121498376,"version":"build-2803163510"},"reference-count":30,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T00:00:00Z","timestamp":1789084800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Funct. Morphol. Kinesiol.","JFMK"],"abstract":"<jats:p>Background and Objectives: Wearable technologies increasingly monitor internal training load in high-performance sport, but their alignment with coach-prescribed physiological objectives remains unclear. This study examined within-athlete associations between WHOOP Activity Strain, coach-prescribed objectives, athlete-perceived load, and completed swimming exposure in one elite junior swimmer. Methods: An exploratory longitudinal single-case secondary analysis was conducted using routinely collected training and athlete-monitoring data from 4 January to 3 July 2026. WHOOP Activity Strain and Session-RPE were synchronized by session, and generalized estimating equations assessed differences across prescribed objectives and variable associations. Results: Of 161 sessions with exact-plan cards, 134 were classified and 128 had strict WHOOP matches. Conventional robust-covariance GEE suggested an objective-related difference (exchangeable p = 0.013; AR(1) p = 0.014), but this was not statistically detectable with the bias-reduced covariance estimator (p = 0.080 and p = 0.075, respectively) and was not reproduced using the legacy classification. WHOOP Activity Strain was consistently associated with Session-RPE Load, Session-RPE, and actual swimming distance. Conclusions: Within this athlete, WHOOP Activity Strain was associated with perceived load and completed swimming distance. Objective-related differences were post hoc and sensitive to the classification source and covariance estimator; they should therefore be considered exploratory and hypothesis-generating.<\/jats:p>","DOI":"10.3390\/jfmk11030369","type":"journal-article","created":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T08:17:42Z","timestamp":1789114662000},"page":"369","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Within-Athlete Associations Between WHOOP Activity Strain, Coach-Prescribed Training Objectives, and Session-RPE in an Elite Junior Swimmer: A Longitudinal Single-Case Study"],"prefix":"10.3390","volume":"11","author":[{"given":"\u00c1rp\u00e1d","family":"Petrov","sequence":"first","affiliation":[{"name":"Doctoral School of Regional and Economic Sciences, Sz\u00e9chenyi Istv\u00e1n University, 9026 Gy\u0151r, Hungary"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"}]},{"given":"Istv\u00e1n","family":"Barthalos","sequence":"additional","affiliation":[{"name":"Department of Health Promotion and Exercise Sciences, Sz\u00e9chenyi Istv\u00e1n University, 9026 Gy\u0151r, Hungary"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"software","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-1976-5045","authenticated-orcid":false,"given":"Daniel","family":"Arany","sequence":"additional","affiliation":[{"name":"Doctoral School of Education, Faculty of Pedagogy and Psychology, E\u00f6tv\u00f6s Lor\u00e1nd University, 1075 Budapest, Hungary"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8729-1706","authenticated-orcid":false,"given":"Katalin","family":"Nagyv\u00e1radi","sequence":"additional","affiliation":[{"name":"Institute of Sport Sciences, Faculty of Education and Psychology, E\u00f6tv\u00f6s Lor\u00e1nd University, 9700 Szombathely, Hungary"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"software","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-0773-1877","authenticated-orcid":false,"given":"Iv\u00e1n","family":"Petrov","sequence":"additional","affiliation":[{"name":"Doctoral School of Health Sciences, Faculty of Health Sciences, University of P\u00e9cs, 7621 P\u00e9cs, Hungary"},{"name":"Heart and Vascular Centre, Semmelweis University, 1085 Budapest, Hungary"},{"name":"Department of Sports Medicine, Semmelweis University, 1085 Budapest, Hungary"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5486-6665","authenticated-orcid":false,"given":"Zolt\u00e1n","family":"Alf\u00f6ldi","sequence":"additional","affiliation":[{"name":"Department of Health Promotion and Exercise Sciences, Sz\u00e9chenyi Istv\u00e1n University, 9026 Gy\u0151r, Hungary"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0213-2237","authenticated-orcid":false,"given":"Ferenc","family":"Ih\u00e1sz","sequence":"additional","affiliation":[{"name":"Department of Health Promotion and Exercise Sciences, Sz\u00e9chenyi Istv\u00e1n University, 9026 Gy\u0151r, Hungary"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"779","DOI":"10.2165\/11317780-000000000-00000","article-title":"The quantification of training load, the training response and the effect on performance","volume":"39","author":"Borresen","year":"2009","journal-title":"Sports Med."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"S139","DOI":"10.1007\/s40279-014-0253-z","article-title":"Monitoring training load to understand fatigue in athletes","volume":"44","author":"Halson","year":"2014","journal-title":"Sports Med."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"S2-161","DOI":"10.1123\/IJSPP.2017-0208","article-title":"Monitoring athlete training loads: Consensus statement","volume":"12","author":"Bourdon","year":"2017","journal-title":"Int. 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