{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,9]],"date-time":"2026-03-09T17:07:21Z","timestamp":1773076041092,"version":"3.50.1"},"reference-count":44,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,3,9]],"date-time":"2026-03-09T00:00:00Z","timestamp":1773014400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Applied Sciences"],"abstract":"<jats:p>This study investigates the performance characteristics of U18 semi-professional soccer players by examining both technical load (TL) and physical load (PL) variables across various playing positions during the 2021\/2022 Spanish Football U18 National League Championship. Methods: Principal Component Analysis (PCA) was employed to simplify the dataset, which comprised 246 match records from 49 athletes (mean age 17.9 \u00b1 0.7 years; height ~177.6 \u00b1 6.3 cm; body mass ~72.0 \u00b1 7.2 kg) across ten matches. This analytical approach aimed to facilitate a deeper understanding of player performance dynamics. Results: Kaiser\u2013Meyer\u2013Olkin (KMO) values varied across positions (technical load: 0.20\u20130.93; physical load: 0.27\u20130.91). This indicates acceptable sampling adequacy for several positional models, but low adequacy for others; therefore, results for positions with low-KMO values should be interpreted cautiously. Factor analysis for both technical and physical load variables identified two components each, explaining substantial total variance (technical load: 63.75\u201386.65%; and physical load: 71.74\u201388.92% across position), with significantly high factor correlations (p &lt; 0.001). The findings further indicate that players occupying defensive positions, such as goalkeepers and center-backs, generally exhibit lower levels of physical intensity and technical engagement compared to their counterparts in more dynamic roles, including full-backs, wingers, and forwards. The latter groups demonstrate higher involvement in high-intensity running and offensive actions. Conclusions: The observed performance patterns highlight the necessity for tailored training programs that align with the specific demands of each playing position. This approach is expected to optimize individual player performance and enhance overall tactical efficiency. Furthermore, the study underscores the importance of developing individualized conditioning strategies that address the unique physical and technical requirements inherent to each role on the field. This analytical approach using PCA provides a more structured and data-driven understanding of these positional differences, reinforming the need for tailored training programs and individualized conditioning strategies.<\/jats:p>","DOI":"10.3390\/app16052596","type":"journal-article","created":{"date-parts":[[2026,3,9]],"date-time":"2026-03-09T10:16:12Z","timestamp":1773051372000},"page":"2596","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Decoding Positional Variability in U18 Semi-Professional Soccer Players: A Principal Component Analysis Utilizing Inertial Measurement Units to Identify Key Determinants"],"prefix":"10.3390","volume":"16","author":[{"given":"Jos\u00e9 Carlos","family":"Barbero-\u00c1lvarez","sequence":"first","affiliation":[{"name":"Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, 18011 Granada, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3575-3507","authenticated-orcid":false,"given":"Jos\u00e9 Antonio S\u00e1nchez","family":"Fuentes","sequence":"additional","affiliation":[{"name":"Research Group Movement Sciences and Sport (MS&SPORT), Department of Physical Activity and Sport, Faculty of Sport Sciences, University of Murcia, 30100 Murcia, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6188-9443","authenticated-orcid":false,"given":"Luis Manuel","family":"Mart\u00ednez-Aranda","sequence":"additional","affiliation":[{"name":"SEJ-680: Science-Based Training (SBT) Research Group, Faculty of Sports Sciences, Pablo de Olavide University, 41013 Seville, Spain"},{"name":"Physical and Sports Performance Research Centre, Faculty of Sports Sciences, Pablo de Olavide University, 41013 Seville, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9813-2842","authenticated-orcid":false,"given":"Filipe Manuel","family":"Clemente","sequence":"additional","affiliation":[{"name":"Department of Biomechanics and Sport Engineering, Gdansk University of Physical Education and Sport, 80-336 Gda\u0144sk, Poland"},{"name":"Sport Physical Activity and Health Research & Innovation Center, Polytechnic University of Coimbra, 3045-093 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1772-1272","authenticated-orcid":false,"given":"Ana Filipa","family":"Silva","sequence":"additional","affiliation":[{"name":"Sport Physical Activity and Health Research & Innovation Center, Polytechnic University of Coimbra, 3045-093 Coimbra, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"990","DOI":"10.47197\/retos.v60.108324","article-title":"Mapeo y tendencias de la investigaci\u00f3n sobre la carga de trabajo en el f\u00fatbol: An\u00e1lisis bibliom\u00e9trico (Soccer training load research mapping and trends: A bibliometric analysis)","volume":"60","author":"Apriantono","year":"2024","journal-title":"Retos"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"902","DOI":"10.1080\/15438627.2023.2297190","article-title":"Relationship between external and internal load indicators and injury using machine learning in professional soccer: A systematic review and meta-analysis","volume":"32","author":"Pillitteri","year":"2024","journal-title":"Res. 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