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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Date results information initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
Caffeine and anaerobic exercise performance: an exploration of caffeine’s effects on performance in young men and the influence of genotype on the variation in responses
Scientific title
The effect of CYP1A2 genotype on the ergogenic effects of caffeine during anaerobic exercise
Secondary ID [1] 298301 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Exercise performance 312931 0
Condition category
Condition code
Musculoskeletal 311422 311422 0 0
Normal musculoskeletal and cartilage development and function
Metabolic and Endocrine 311638 311638 0 0
Normal metabolism and endocrine development and function

Study type
Description of intervention(s) / exposure
Caffeine supplementation.
Dose: 3 mg per kg of body weight
The duration of administration: only on one occasion.
Mode of administration: oral tablet.
Wash out period between the caffeine and placebo conditions is from 4 to 7 days.
The CYP1A2 genotype will be assessed using a buccal swab sample collected before the caffeine and placebo conditions.
Intervention code [1] 314536 0
Other interventions
Comparator / control treatment
Composition of the placebo treatment: glucose capsule,
Control group

Primary outcome [1] 320143 0
Primary Outcome 1: vertical jump height and power assessed using a countermovement jump on a force platform.
Timepoint [1] 320143 0
One hour post caffeine and placebo ingestion.
Primary outcome [2] 320340 0
Primary Outcome 2: barbell velocity in the bench press exercise assessed using linear position transducers.
Timepoint [2] 320340 0
One hour post caffeine and placebo ingestion.
Primary outcome [3] 320341 0
Primary Outcome 3: maximal number of repetitions in an upper-body muscle endurance test.
Timepoint [3] 320341 0
One hour post caffeine and placebo ingestion.
Secondary outcome [1] 370691 0
Secondary Outcome 1: side-effects to caffeine ingestion such as tachycardia, self-reported by the participants.
Timepoint [1] 370691 0
Immediately post testing and upon waking up in the morning after testing.
Secondary outcome [2] 371274 0
Primary Outcome 4: mean and peak power in the Wingate test.
Timepoint [2] 371274 0
One hour post caffeine and placebo ingestion.

Key inclusion criteria
The sample size will consist of resistance-trained men. Resistance-trained men will be defined as having a minimum of 6 months of resistance training experience with a minimum weekly training frequency of two times on most weeks.
Minimum age
18 Years
Maximum age
40 Years
Can healthy volunteers participate?
Key exclusion criteria
The exclusion criteria will be: (1) current smoker; (2) prior or current use of anabolic steroids; and (3) existence of health limitations.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation is not concealed.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using a randomisation table created by computer software (i.e. computerised sequence generation)
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
Intervention assignment
Other design features
Phase 0
Type of endpoint/s
Statistical methods / analysis
In order to calculate the sample size, we used the G*Power software, version 3.1. The expected effect size was 0.25, which is the average effect size across all meta-analyses that examined the effects of caffeine on exercise performance (Grgic et al. 2019). Here, the alpha error level was set at 0.05 and the statistical power was at 80%. The correlation between repeated measures was set at 0.75 which was determined by our previously published data (Grgic and Mikulic, 2017) and previous review papers (Polito et al., 2016). Based on this power analysis, the total required sample size for this study is 18 participants. Two-way ANOVAs (experimental treatment x genotype group) will be done for the analysis of the data. In addition, absolute and relative effect sizes (i.e. absolute differences between means and Cohen’s d values, respectively) will be calculated.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment postcode(s) [1] 26560 0
3011 - Footscray
Recruitment postcode(s) [2] 26561 0
3032 - Maribyrnong

Funding & Sponsors
Funding source category [1] 302843 0
Name [1] 302843 0
Victoria University
Country [1] 302843 0
Primary sponsor type
Victoria University
PO Box 14428, Melbourne, Vic 8001, Australia; Street address: Footscray Park Campus, Ballarat Road, Footscray 3011
Secondary sponsor category [1] 302791 0
Name [1] 302791 0
Address [1] 302791 0
Country [1] 302791 0

Ethics approval
Ethics application status
Ethics committee name [1] 303421 0
Victoria University Human Research Ethics Committee
Ethics committee address [1] 303421 0
PO Box 14428, Melbourne, Vic 8001, Australia; Street address: Footscray Park Campus, Ballarat Road, Footscray 3011
Ethics committee country [1] 303421 0
Date submitted for ethics approval [1] 303421 0
Approval date [1] 303421 0
Ethics approval number [1] 303421 0

Brief summary
The aim of the study will be to investigate the effects of caffeine (3 mg/kg 60 min pre-exercise) on vertical jump performance, movement velocity in resistance exercise, muscular endurance, and power output. Additionally, the aim is to explore if the inter-individual variation in responses to caffeine ingestion influenced by variations in genotype. The study hypothesis is that individuals classified as AA genotype will experience greater improvements in exercise performance following caffeine ingestion than those with AC and CC genotypes.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 93622 0
Prof David Bishop
Address 93622 0
Victoria University, Melbourne
Footscray Park Campus | Ballarat Road | Footscray VIC 3001
PO Box 14428
Country 93622 0
Phone 93622 0
+61 0435 962 364
Fax 93622 0
Email 93622 0
Contact person for public queries
Name 93623 0
Mr Jozo Grgic
Address 93623 0
Victoria University, Melbourne
Footscray Park Campus | Ballarat Road | Footscray VIC 3001
PO Box 14428
Country 93623 0
Phone 93623 0
+61 0459337908
Fax 93623 0
Email 93623 0
Contact person for scientific queries
Name 93624 0
Mr Jozo Grgic
Address 93624 0
Victoria University, Melbourne
Footscray Park Campus | Ballarat Road | Footscray VIC 3001
PO Box 14428
Country 93624 0
Phone 93624 0
+61 0459337908
Fax 93624 0
Email 93624 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
What data in particular will be shared?
All data.
When will data be available (start and end dates)?
Immediately following publication, no end date.
Available to whom?
Only researchers who provide a methodologically sound proposal.
Available for what types of analyses?
Only to achieve the aims in the approved proposal.
How or where can data be obtained?
Individual participant data will be available based on a request to the corresponding author.

What supporting documents are/will be available?

No Supporting Document Provided

Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.