]>
IRCT20190530043762N5 IRCT 2026-10-02 Shiraz University Effects of Caffeine, L-Theanine, and Their Combination on Physical Performance in Adolescent Soccer Players Acute Effects of Caffeine, L-Theanine, and Their Combination on Sprint, Jump, Change-of-Direction, and Repeated-Sprint Performance in Trained Adolescent Soccer Players: A Randomized, Double-Blind, Crossover Trial 2026-10-07 anticipated 16 Complete https://irct.ir/trial/92384 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Crossover, Purpose: Supportive, Randomization description: Randomization will be performed at the individual level using a simple randomization procedure. Four balanced treatment sequences will be predetermined for allocation of participants to the four treatment sequences. These four sequences will be: caffeine–caffeine and L-theanine combination–placebo–L-theanine; L-theanine–caffeine–caffeine and L-theanine combination–placebo; placebo–L-theanine–caffeine–caffeine and L-theanine combination; and caffeine and L-theanine combination–placebo–L-theanine–caffeine. Each sequence will be written on four identical cards; therefore, a total of 16 sequence cards will be prepared. In addition, the identification number of each of the 16 participants will be written on a separate identical card. The sequence cards and participant identification cards will be placed in two separate opaque containers. Random allocation will be performed by an independent investigator who will not be involved in intervention administration, outcome assessment, or experimental procedures. At each allocation step, one sequence card will be randomly drawn from the sequence container and one participant identification card will then be randomly drawn from the second container. The selected participant will be assigned to the treatment sequence indicated on the selected sequence card. This procedure will be repeated until all 16 participants have been allocated, resulting in four participants assigned to each treatment sequence. The unit of randomization will be the individual participant, and neither cluster randomization nor stratified randomization will be used. The random sequence will be generated and allocated using a manual lottery procedure with identical and indistinguishable cards, and no statistical software or random-number table will be used. For allocation concealment, the treatment-sequence cards will be kept in a separate container from the participant-identification cards. The investigator responsible for randomization will be independent of the researchers involved in intervention administration and outcome assessment. Therefore, the treatment sequence assigned to each participant will not be known until the lottery procedure has been performed and the cards have been drawn from the two separate containers, Blinding description: The study will be conducted using a double-blind design. Participants will be blinded to the identity of the capsules and will not be informed of their assigned treatment condition. Active and placebo capsules will be visually identical and will be administered in the same number and manner across all experimental conditions. The investigators responsible for performance testing and outcome assessment will also remain blinded to treatment allocation throughout all stages of data collection. The statistical analyst will likewise be blinded to treatment identity during the statistical analyses, with the experimental conditions represented by treatment codes rather than their actual condition names. The treatment codes will be maintained by an investigator who will not be involved in outcome assessment. These codes will not be disclosed to the research team or the statistical analyst until completion of all experimental procedures and the primary statistical analyses. Thus, the identity of the treatment conditions will remain concealed throughout the experimental procedures and primary statistical analyses. 3 Physical Activity and Exercise Performance. Intervention 1: Placebo condition: In this condition, participants will receive two capsules that are visually identical to the active ingredient capsules. One capsule will serve as the caffeine placebo and the other as the L-theanine placebo. Both capsules will be ingested simultaneously 60 minutes prior to the commencement of the functional tests.”. Intervention 2: First intervention group_ Caffeine condition: Participants will ingest one capsule containing caffeine (3 mg·kg⁻¹ body mass) and one L-theanine placebo capsule. Both capsules will be ingested simultaneously 60 minutes prior to the commencement of the functional tests. Intervention 3: Second intervention group _ L-Theanine Condition: In this condition, participants will receive one caffeine placebo capsule and one capsule containing L-theanine at a dose of 3 mg·kg⁻¹ of body mass. Both capsules will be ingested simultaneously 60 minutes prior to the commencement of the functional tests. Intervention 4: Third intervention group _ Caffeine + L-Theanine Condition: In this condition, participants will receive one capsule containing caffeine at a dose of 3 mg·kg⁻¹ of body mass and one capsule containing L-theanine at a dose of 3 mg·kg⁻¹ of body mass. Both capsules will be ingested simultaneously 60 minutes prior to the commencement of the functional tests. Yes - There is a plan to make this available What will be shared: De-identified individual participant data will be made available in a public data repository or as a supplementary file to the article following the publication of the study results. Prior to sharing, all data will be processed to remove participant-identifying information. The study protocol will be made available as a supplementary file to the article or in a public scientific repository after the study is completed and the main results are published. The statistical analysis plan will be made available as a supplementary file to the article or in a public scientific repository after the study is completed and the main results are published. A data dictionary—including variable names, definitions, units of measurement, and coding schemes—will be made available alongside the de-identified individual participant data. When: The period for accessing data and documentation will begin one week after the publication of the results. To whom: Researchers working in academic and scientific institutions Conditions: The study data and documentation may be used solely for research and scientific purposes, including conducting secondary research, re-analyzing data, and verifying or replicating study results. Access to individual-level data is contingent upon the de-identification of participant information and adherence to principles of confidentiality, privacy, and ethical requirements regarding the use of research data. Data usage must be strictly confined to scientific and research objectives, with no attempt to re-identify participants Where to obtain: Applicants may request access to the study's data and documentation by contacting the principal investigator or corresponding author via the email address listed on the study's official webpage or in the published article. The designated contact person is Dr. Alireza Niknam (email: Alireza73.Niknam@gmail.com). Requests will be evaluated based on the research objective and verification that participant confidentiality and anonymity are maintained; upon approval, the relevant data or documentation will be provided to the applicant. How to obtain: Requests for data or documentation will be reviewed by the principal investigator or the research team. The applicant must specify the purpose and intended use of the requested data or documentation. Following the initial review, the request will be evaluated for alignment with scientific objectives, adherence to confidentiality requirements, and the assurance of participant anonymity. Upon approval, the requested data or documentation will be provided to the applicant in an appropriate format. The use of data to re-identify participants or for purposes inconsistent with research ethics principles is prohibited. Comments:
public Alireza Niknam
Vahdat Sports Complex, Shiraz University Cultural Complex, West Coastal Street, Shiraz
Shiraz Iran (Islamic Republic of) 7134868164 +98 71 3613 3318 alireza.niknam@yahoo.com Shiraz University scientific Alireza Niknam
Vahdat Sports Complex, Shiraz University Cultural Complex, West Coastal Street, Shiraz
Shiraz Iran (Islamic Republic of) 7134868164 +98 71 3613 3318 alireza.niknam@yahoo.com Shiraz University Iran (Islamic Republic of) The age range should be 16 to 18 years. The Body Mass Index (BMI) should be within the normal range (18.5–24.5). The gender of the samples must be male. The subjects must have at least two years of experience participating in regular soccer training. The participants' general health must be confirmed by a physician. Participants must not have a known sensitivity to caffeine or theanine. 16 years 18 years Male History of musculoskeletal injury preventing participation in sports activities Use of prohibited ergogenic substances according to the World Anti-Doping Agency. Lack of consent from participants to take part in the study process. Y93.B Activities involving other muscle strengthening exercises Placebo Rehabilitation Rehabilitation Rehabilitation Placebo condition: In this condition, participants will receive two capsules that are visually identical to the active ingredient capsules. One capsule will serve as the caffeine placebo and the other as the L-theanine placebo. Both capsules will be ingested simultaneously 60 minutes prior to the commencement of the functional tests.” First intervention group_ Caffeine condition: Participants will ingest one capsule containing caffeine (3 mg·kg⁻¹ body mass) and one L-theanine placebo capsule. Both capsules will be ingested simultaneously 60 minutes prior to the commencement of the functional tests. Second intervention group _ L-Theanine Condition: In this condition, participants will receive one caffeine placebo capsule and one capsule containing L-theanine at a dose of 3 mg·kg⁻¹ of body mass. Both capsules will be ingested simultaneously 60 minutes prior to the commencement of the functional tests. Third intervention group _ Caffeine + L-Theanine Condition: In this condition, participants will receive one capsule containing caffeine at a dose of 3 mg·kg⁻¹ of body mass and one capsule containing L-theanine at a dose of 3 mg·kg⁻¹ of body mass. Both capsules will be ingested simultaneously 60 minutes prior to the commencement of the functional tests. The 20-meter sprint time will be measured as the time required to cover a distance of 20 meters at maximum possible speed. Following a standard warm-up, participants will perform three maximal-effort sprints, with a minimum of one minute of passive rest between trials. The time for each trial will be recorded using an optical timing system, and the fastest time_measured in seconds_will be taken as the outcome value for each testing session. Timepoint: The 20-meter sprint time during each of the four testing sessions will be measured at two time points: first, following a standard warm-up and prior to the start of the repeated-sprint test; and second, immediately after the completion of the repeated-sprint test and a two-minute rest period. The four testing sessions will be conducted with a seven-day washout period between them. Method of measurement: DesiKala digital optical timing device with a measurement precision of 0.001 seconds. The standing long jump distance is measured as the horizontal distance from the starting line to the point where the heel makes its nearest contact with the ground following a maximal jump. After a standard warm-up, participants will perform three maximal-effort trials, with a one-minute passive rest period between attempts. The longest jump recorded, measured in centimeters, will be taken as the outcome value for the testing session. Timepoint: Standing long jump distance will be measured at two time points during each of the four testing sessions: first, following a standard warm-up and prior to the repeated sprint test; and second, immediately after the completion of the repeated sprint test and a two-minute rest period. The four testing sessions will be conducted with a seven-day washout period between them. Method of measurement: A graduated, standard tape measure for measuring the horizontal jump distance, with results recorded in centimeters. Change-of-direction time will be measured as the time required to complete the standard Illinois change-of-direction test at maximum speed. Participants will perform two maximal-effort trials, with a two-minute passive rest period between them. The completion time for each trial will be recorded using an optical timing system, and the fastest time—measured in seconds—will be taken as the outcome value for each testing session. Timepoint: The change-of-direction test time during each of the four experimental sessions will be measured at two time points: first, following a standard warm-up and prior to the repeated-sprint test; and second, immediately after the completion of the repeated-sprint test and a two-minute rest period. The four experimental sessions will be conducted with a seven-day washout period between them. Method of measurement: DesiKala digital optical timing device with a measurement precision of 0.001 seconds. Rate of Perceived Exertion (RPE) will be measured as the participants’ subjective perception of the exertion intensity resulting from the Repeated Sprint Test. This variable will be recorded using the 10-point Rating of Perceived Exertion scale (Borg CR10 scale). Timepoint: The Rate of Perceived Exertion (RPE) will be recorded at each of the four experimental sessions: immediately before the start of the Repeated Sprint Test and immediately following the completion of each of the three test blocks. Thus, four measurements will be taken per session, consisting of one pre-test measurement and three post-exercise measurements (after the first, second, and third blocks, respectively). The four experimental sessions will be separated by a seven-day washout period. Method of measurement: Borg 10-point Category-Ratio (CR10) scale. Shiraz University Approved 2026-07-15 Research Ethics Committees of Faculty of Psychology and Educational Sciences Jomhoori Eslami Blvd Shiraz Fars Iran (Islamic Republic of)