Time-of-Day Modulates Caffeine Ergogenicity in Adolescent Futsal Players: Effects on Repeated-Sprint Performance, Readiness, and Mood

Determining the Effect of Time of Day on the Ergogenic Effects of Acute Caffeine Ingestion in Adolescent Futsal Players: Effects on Repeated-Sprint Performance, Readiness, and Mood

This study is a randomized, double-blind, placebo-controlled, counterbalanced crossover trial conducted on 24 adolescent futsal players.

Testing sessions are conducted in an indoor futsal facility under standardized environmental conditions in Islamic Azad University Shahrekord branch. Morning trials are performed between 08:00 and 09:00 h and evening trials between 17:00 and 18:00 h. Playing surface, footwear, testing equipment, warm-up, recovery intervals, and verbal instructions are standardized across sessions.

Participants are male adolescent futsal players aged 14–18 years with at least 2 years of structured futsal training and at least 3 training sessions per week. Individuals with recent injury, sleep-related disorders, use of medications affecting performance or sleep, high habitual caffeine intake, caffeine hypersensitivity are excluded.

Each participant completes four experimental conditions in a crossover design: caffeine in the morning, placebo in the morning, caffeine in the evening, and placebo in the evening. Anhydrous caffeine at a dose of 3 milligrams per kilogram of body mass or placebo in the form of microcrystalline cellulose is ingested 60 minutes before testing. A washout interval of at least 72 hours separates the experimental sessions.

Mean time of the Repeated Sprint Ability test, The best time and total time of the Repeated Sprint Ability test , Repeated Sprint Ability decrement, Countermovement Jump height , 10- and 20-m sprint times, Illinois agility test time, Rate of Perceived Exertion , alertness, fatigue, motivation, readiness to perform, Brunel Mood Scale indices.

Caffeine and placebo capsules are identical in shape, color, size, appearance, and packaging. Caffeine is administered as anhydrous caffeine at 3 mg·kg⁻¹ body mass, and placebo capsules contain microcrystalline cellulose. Supplement preparation, coding, and packaging are performed by an independent person. Participants, coaches, outcome assessors, researchers present during testing, and data analysts remain blinded to supplement allocation until completion of analyses. After each experimental trial, participants’ guesses regarding supplement identity are recorded to evaluate blinding success.

Performance, perceptual, mood, and safety data across morning caffeine, morning placebo, evening caffeine, and evening placebo conditions. after deidentification, data will include RSA indices, CMJ, sprint, agility, RPE, VAS, BRUMS, and adverse-symptom variables.

From publication of the article for 6 months

Academic and scientific researchers with a reasonable request and a clearly specified research purpose.

Data may be used only for scientific purposes, reanalysis, meta-analysis, or methodological review; commercial use or attempts to identify participants are not permitted.

From the corresponding author manager

Requests should be submitted by email and include the research purpose, requested data, and planned analyses. After review and approval, data will be shared as a secure digital file. Estimated review time: 2–4 weeks.