{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T18:29:44Z","timestamp":1791570584785,"version":"4.3.4"},"reference-count":57,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2024,7,26]],"date-time":"2024-07-26T00:00:00Z","timestamp":1721952000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>There is evidence that both intra-serial variable resistance (I-sVR), as pre-activation within the post-activation performance enhancement cycle (PAPE), and creatine and caffeine supplementation increase athletic performance in isolation. However, the effect of the three conditioning factors on 30 m repeated sprint ability (RSA) performance in young soccer players is unknown. This study determined the summative and isolation effect of ergogenic aids and pre-activation in half-back squats (HBSs) with I-sVR on performance in an RSA test in young soccer players. Twenty-eight young soccer players were randomly assigned to either EG1 (n = 7, creatine + caffeine + I-sVR), EG2 (n = 7, creatine + placebo2 + I-sVR), EG3 (n = 7, placebo1 + caffeine + I-sVR), or EG4 (n = 7, placebo1 + placebo2 + I-sVR), using a factorial, four-group-matched, double-blind, placebo-controlled design. Creatine supplementation included 0.3 g\/kg\/day for 14 days, caffeine supplementation included 0.3 mg\/kg per day, and pre-activation in HBS with I-sVR (1 \u00d7 5 at 30% 1RM [1.0\u20131.1 m\/s] + 1 \u00d7 4 at 60% 1RM [0.6\u20130.7 m\/s]). The RSA test and HBS outcomes were evaluated. Three-way ANOVA showed non-significant differences for the RSA test and HBS outcomes (p &gt; 0.05). At the end of this study, it was found that the three ergogenic aids, together, do not generate a summative effect on the physical performance of young soccer players. However, it is important to analyze individual responses to these specific protocols.<\/jats:p>","DOI":"10.3390\/nu16152437","type":"journal-article","created":{"date-parts":[[2024,7,26]],"date-time":"2024-07-26T13:04:59Z","timestamp":1721999099000},"page":"2437","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Combined Impact of Creatine, Caffeine, and Variable Resistance on Repeated Sprint Ability in Young Soccer Players"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6871-098X","authenticated-orcid":false,"given":"\u00c1lvaro","family":"Huerta Ojeda","sequence":"first","affiliation":[{"name":"N\u00facleo de Investigaci\u00f3n en Salud, Actividad F\u00edsica y Deporte ISAFYD, Universidad de Las Am\u00e9ricas, Vi\u00f1a del Mar 2531098, Chile"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4091-1709","authenticated-orcid":false,"given":"Carlos","family":"Jorquera-Aguilera","sequence":"additional","affiliation":[{"name":"Facultad de Ciencias, Escuela de Nutrici\u00f3n y Diet\u00e9tica, Universidad Mayor, Santiago 8580745, Chile"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,7,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1703","DOI":"10.1519\/JSC.0000000000004447","article-title":"Linear and Change of Direction Repeated Sprint Ability Tests: A Systematic Review","volume":"37","author":"Kyles","year":"2023","journal-title":"J. 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