{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,10]],"date-time":"2026-10-10T22:14:31Z","timestamp":1791670471533,"version":"4.3.4"},"reference-count":46,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2026,5,9]],"date-time":"2026-05-09T00:00:00Z","timestamp":1778284800000},"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>Objective: This study compared the acute effects of caffeine capsule ingestion and caffeine mouth rinsing on physical performance and volleyball-specific skills at different times of day in trained adolescent male volleyball players. Methods: Twenty-four well-trained male volleyball players (age: 16.9 \u00b1 0.7 years) completed a randomized, double-blind, placebo-controlled crossover study involving three supplementation conditions, caffeine capsule (CAFcap, 3 mg\u00b7kg\u22121), caffeine mouth rinse (CAFrinse, 3 mg\u00b7kg\u22121), and placebo (PLA), administered via a double-dummy procedure (nine sessions per participant: 3 conditions \u00d7 3 times of day) at 08:00, 12:00, and 18:00. Participants completed squat jump (SJ), countermovement jump (CMJ), block jump, attack jump, 10 \u00d7 10 m t-test, spike accuracy, and serve accuracy assessments. Data were analyzed using two-way repeated-measures ANOVA. Results: Significant main effects of condition and time of day were observed for all outcomes. Significant condition \u00d7 time-of-day interactions were found for SJ, CMJ, attack jump, and change-of-direction speed, indicating that caffeine-related ergogenic effects were most evident in the morning and at midday, whereas these benefits were attenuated in the evening when baseline performance was highest. At 08:00 and 12:00, both CAFcap and CAFrinse improved jump performance and agility compared with PLA, with capsule ingestion showing a small-to-moderate advantage over mouth rinsing for selected lower-limb power outcomes at midday (mean difference range: 0.51\u20130.57 cm; dz = 0.57\u20130.65). For block jump, spike accuracy, and serve accuracy, both caffeine conditions improved performance relative to placebo, while a progressive improvement across the day was observed under all conditions, including placebo, confirming a diurnal rhythm effect independent of supplementation. Overall, the data indicate that caffeine partially reduced the amplitude of diurnal variation in several physical performance measures. Conclusions: Both caffeine capsule ingestion and caffeine mouth rinsing enhanced physical and volleyball-specific performance in trained adolescent male volleyball players. The ergogenic effects were more pronounced earlier in the day, suggesting that caffeine may be particularly useful for attenuating morning and midday performance decrements, while mouth rinsing represents a practical non-ingestive alternative with meaningful efficacy.<\/jats:p>","DOI":"10.3390\/nu18101514","type":"journal-article","created":{"date-parts":[[2026,5,11]],"date-time":"2026-05-11T12:05:22Z","timestamp":1778501122000},"page":"1514","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Differential Time-of-Day Effects of Caffeine Capsule and Mouth Rinse on Physical Performance and Volleyball-Specific Skills in Adolescent Male Volleyball Players"],"prefix":"10.3390","volume":"18","author":[{"given":"Salma Belhaj","family":"Amor","sequence":"first","affiliation":[{"name":"Physical Activity, Sport and Health Research Unit (UR18JS01), National Observatory of Sports, Tunis 1003, Tunisia"},{"name":"High Institute of Sports and Physical Education of El Kef, University of Jendouba, El Kef 7100, Tunisia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6221-546X","authenticated-orcid":false,"given":"Wissem","family":"Dhahbi","sequence":"additional","affiliation":[{"name":"Research Unit (UR22JS01) \u201cSport Sciences, Health and Movement\u201d, High Institute of Sport and Physical Education of Kef, University of Jendouba, El Kef 7100, Tunisia"},{"name":"Training Department, Police College, Qatar Police Academy, Doha 7157, Qatar"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-3387-9886","authenticated-orcid":false,"given":"Marouen","family":"Souaifi","sequence":"additional","affiliation":[{"name":"Research Unit (UR22JS01) \u201cSport Sciences, Health and Movement\u201d, High Institute of Sport and Physical Education of Kef, University of Jendouba, El Kef 7100, Tunisia"},{"name":"Training Department, Police College, Qatar Police Academy, Doha 7157, Qatar"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-2214-4667","authenticated-orcid":false,"given":"Halil \u0130brahim","family":"Ceylan","sequence":"additional","affiliation":[{"name":"Physical Education of Sports Teaching Department, Faculty of Sports Sciences, Atat\u00fcrk University, 25240 Erzurum, T\u00fcrkiye"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4254-3105","authenticated-orcid":false,"given":"Johnny","family":"Padulo","sequence":"additional","affiliation":[{"name":"Department of Biomedical Sciences for Health (SCIBIS), Universit\u00e0 Degli Studi di Milano, 20134 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7302-4191","authenticated-orcid":false,"given":"Stefano","family":"Vando","sequence":"additional","affiliation":[{"name":"Fitkion\u2014Center for Kinesiology and Adapted Physical Activity, 04100 Latina, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nagihan Bur\u00e7ak","family":"Ceylan","sequence":"additional","affiliation":[{"name":"Graduate Education Institute, Bayburt University, 69000 Bayburt, T\u00fcrkiye"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4615-6687","authenticated-orcid":false,"given":"Raul Ioan","family":"Muntean","sequence":"additional","affiliation":[{"name":"Department of Physical Education and Sport, Faculty of Law and Social Sciences, University \u201c1 Decembrie 1918\u201d of Alba Iulia, 510009 Alba Iulia, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1227-8221","authenticated-orcid":false,"given":"Nizar","family":"Souissi","sequence":"additional","affiliation":[{"name":"Physical Activity, Sport and Health Research Unit (UR18JS01), National Observatory of Sports, Tunis 1003, Tunisia"},{"name":"High Institute of Sport and Physical Education, University of Manouba, Ksar-Said, Manouba 2010, Tunisia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1123\/ijspp.1.2.95","article-title":"The development of a standardized skill assessment for junior volleyball players","volume":"1","author":"Gabbett","year":"2006","journal-title":"Int. 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