Maximum ForceNCT07726745
The Effects of Caffeine and Vitamin C on Maximum Strength and Strength Endurance in Adolescents With Mild Mental Fatigue
A study testing 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses in people with Maximum Force and Strength Endurance, run by Yunliang Zhang.
Trial summary
Objective To investigate the independent and combined effects of caffeine and vitamin C on maximal strength and strength endurance in female adolescents with mild mental fatigue. Methods A randomised, double-blind, crossover experimental design was adopted. Read more about this study
- Who is it for?
- Ages 18 to 19 years, women only
- Conditions the study is for
- Maximum Force, Strength Endurance, Mental Fatigue
- What is being tested?
- 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 40 participants
- Where
- No sites listed yet
- Study dates
- 25 Jul 2026to 22 Sep 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 19 years
- Women only
- No healthy volunteers
- Adult
Who may be able to join
- Aged between 18and 19years (adolescent)
- Able to complete standardized 1RM maximal strength test and muscular endurance protocol for back squat and bench press
- Meet criteria for mild mental fatigue verified by validated scale (PVT + VAS Mental Fatigue ≥4/10 or Brief Fatigue Inventory) prior to experimental session
- Habitual daily caffeine intake ≤ 150 mg/day (low-to-moderate habitual consumption)
- Non-smoker; no regular alcohol consumption
- Consistent strength training status: No physical training for the past 3 months, or maintenance of a consistent daily activity routine throughout the study
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- Able to attend all scheduled testing visits, comply with pre-test restrictions (diet, sleep, exercise, supplements)
- Participant provides written assent; parent/legal guardian provides written informed consent
- Able to understand and follow verbal and written study instructions
Who cannot join
- History of cardiovascular disease, arrhythmia, hypertension, asthma requiring regular medication
- Known hypersensitivity or adverse reaction to caffeine, vitamin C
- Chronic neurological disorders: epilepsy, migraine disorder, ADHD with stimulant medication
- Current psychiatric diagnosis (anxiety, depression) receiving psychotropic medication
- Musculoskeletal injury in the past 3 months limiting lower/upper body maximal strength testing
- Regular intake of ergogenic supplements (creatine, beta-alanine, energy drinks) within 4 weeks before screening
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- Use of any stimulants, anti-fatigue drugs, corticosteroids within 30 days prior to enrollment
- Chronic gastrointestinal disease, kidney stone history (vitamin C related risk)
- Irregular sleep-wake cycle, diagnosed sleep disorder
- Females: current pregnancy; regular oral contraceptive use
- Participated in other human intervention trials within past 8 weeks
- Investigator judges any condition that compromises participant safety or interferes with outcome measurements
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
About this study
Objective To investigate the independent and combined effects of caffeine and vitamin C on maximal strength and strength endurance in female adolescents with mild mental fatigue.
Methods A randomised, double-blind, crossover experimental design was adopted. Forty female college students presenting mild mental fatigue were recruited as participants. Each participant completed five laboratory sessions in total. The first session determined their one-repetition maximum (1RM) for bench press and back squat. The remaining four experimental sessions involved four supplement interventions administered in random order: placebo control, vitamin C (VC) alone, caffeine (CAF) alone, and combined caffeine plus vitamin C (CAF+VC). A one-week washout interval was arranged between every two supplementation trials.
Read more
In each test session, participants completed a 45-min Stroop task to induce mental fatigue prior to exercise assessments. Measurements included the Visual Analogue Scale for Mental Fatigue (VAS-MF), 1RM bench press and squat performance, as well as the maximal number of repetitions at 65% 1RM for both movements. Immediately after the strength endurance test, perceived exertion and muscle pain were rated. Blood glucose and blood lactate concentrations were sampled before and after all exercise protocols.
Supplementation was administered 1 hour prior to testing: a standard caffeine dosage of 3.0 mg per kg body mass and a single 500 mg dose of vitamin C were provided for the corresponding intervention groups.
- Conditions
- Maximum Force, Strength Endurance, Mental Fatigue
- Being tested
- 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses
- Medical subject headings
- Mental Fatigue
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench pressesBehavioural
A randomized, double-blind, crossover design was employed. Professional coaches assessed the subjects' bench press and back squat performances to examine the effects of caffeine combined with vitamin C on maximum strength (1RM) and strength endurance (repetitions to failure at 65% of 1RM) during bench press and back squat training. 65% of 1RM is a widely recognized load for strength endurance testing [28]. The formal experiment consisted of five test sessions: one for familiarization with the entire experimental procedure and a preliminary 1RM test to reconfirm the 1RM measured three weeks prior to the study. The remaining four sessions were conducted sequentially for the control group, vitamin C (VC), caffeine (CAF), and caffeine plus vitamin C (CAF+VC) groups. Each test was spaced 7 days apart to eliminate carryover effects [30]. All tests were scheduled between 12:00 PM and 4:00 PM to control for the effects of circadian rhythms [30].
| Study group | Role | What they receive |
|---|---|---|
| caf | Experimental | Not described Receives: Behavioral: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses |
| VC | Experimental | Not described Receives: Behavioral: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses |
| caf+VC | Experimental | Not described Receives: Behavioral: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses |
| Control | Experimental | Not described Receives: Behavioral: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses |
What is being measured
The primary outcome is the main question the study is designed to answer.
1RM Squats and Bench Presses；Number of repetitions for 65% 1RM squats and bench presses
Measured: 5 week
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Jul 2026
- Study start25 Jul 2026 (estimated)
- Primary completion20 Sep 2026 (estimated)
- Study completion22 Sep 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Maximum ForceStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Yunliang Zhang
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor-investigator, Yunliang Zhang, Tianjin University of Sport
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07726745
- Sponsor's protocol ID
- TJUS2026-30
- Status last verified
- Jul 2026
- First submitted
- 17 Jul 2026
- Last updated
- 27 Jul 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: http://www.medresman.org.cn/login.aspx
Study at a glance
From the registry record, last updated by the sponsor on 27 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effects of Caffeine and Vitamin C on Maximum Strength and Strength Endurance in Adolescents With Mild Mental Fatigue
- ClinicalTrials.gov ID
- NCT07726745
- Acronym / sponsor ID
- TJUS2026-30
- Conditions
- Maximum Force, Strength Endurance, Mental Fatigue
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- Yunliang ZhangUniversity, hospital or other
- Study start
- 25 Jul 2026 (estimated)
- Primary completion
- 20 Sep 2026 (estimated)
- Study completion
- 22 Sep 2026 (estimated)
- First posted
- 24 Jul 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Objective To investigate the independent and combined effects of caffeine and vitamin C on maximal strength and strength endurance in female adolescents with mild mental fatigue.
Methods A randomised, double-blind, crossover experimental design was adopted. Forty female college students presenting mild mental fatigue were recruited as participants. Each participant completed five laboratory sessions in total. The first session determined their one-repetition maximum (1RM) for bench press and back squat. The remaining four experimental sessions involved four supplement interventions administered in random order: placebo control, vitamin C (VC) alone, caffeine (CAF) alone, and combined caffeine plus vitamin C (CAF+VC). A one-week washout interval was arranged between every two supplementation trials.
In each test session, participants completed a 45-min Stroop task to induce mental fatigue prior to exercise assessments. Measurements included the Visual Analogue Scale for Mental Fatigue (VAS-MF), 1RM bench press and squat performance, as well as the maximal number of repetitions at 65% 1RM for both movements. Immediately after the strength endurance test, perceived exertion and muscle pain were rated. Blood glucose and blood lactate concentrations were sampled before and after all exercise protocols.
Supplementation was administered 1 hour prior to testing: a standard caffeine dosage of 3.0 mg per kg body mass and a single 500 mg dose of vitamin C were provided for the corresponding intervention groups.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- Double blind (participant, investigator)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| caf | Experimental | Behavioral: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses |
| VC | Experimental | Behavioral: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses |
| caf+VC | Experimental | Behavioral: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses |
| Control | Experimental | Behavioral: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses |
Who may qualify
- Ages
- 18 to 19 years
- Sex
- Female only
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (9 listed)
- Aged between 18and 19years (adolescent)
- Able to complete standardized 1RM maximal strength test and muscular endurance protocol for back squat and bench press
- Meet criteria for mild mental fatigue verified by validated scale (PVT + VAS Mental Fatigue ≥4/10 or Brief Fatigue Inventory) prior to experimental session
- Habitual daily caffeine intake ≤ 150 mg/day (low-to-moderate habitual consumption)
- Non-smoker; no regular alcohol consumption
Key exclusion criteria (12 listed)
- History of cardiovascular disease, arrhythmia, hypertension, asthma requiring regular medication
- Known hypersensitivity or adverse reaction to caffeine, vitamin C
- Chronic neurological disorders: epilepsy, migraine disorder, ADHD with stimulant medication
- Current psychiatric diagnosis (anxiety, depression) receiving psychotropic medication
- Musculoskeletal injury in the past 3 months limiting lower/upper body maximal strength testing
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench pressesA randomized, double-blind, crossover design was employed. Professional coaches assessed the subjects' bench press and back squat performances to examine the effects of caffeine combined with vitamin C on maximum strength (1RM) and strength endurance (repetitions to failure at 65% of 1RM) during bench press and back squat training. 65% of 1RM is a widely recognized load for strength endurance testing [28]. The formal experiment consisted of five test sessions: one for familiarization with the entire experimental procedure and a preliminary 1RM test to reconfirm the 1RM measured three weeks prior to the study. The remaining four sessions were conducted sequentially for the control group, vitamin C (VC), caffeine (CAF), and caffeine plus vitamin C (CAF+VC) groups. Each test was spaced 7 days apart to eliminate carryover effects [30]. All tests were scheduled between 12:00 PM and 4:00 PM to control for the effects of circadian rhythms [30]. | Behavioural | Control, VC, caf, caf+VC |
Primary outcome
1RM Squats and Bench Presses；Number of repetitions for 65% 1RM squats and bench presses
Time frame: 5 week
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 27 Jul 2026.
- Individual participant dataSharing planned: Yes. http://www.medresman.org.cn/login.aspx
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Questions about this trial
What is this clinical trial studying?
A study testing 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses in people with Maximum Force and Strength Endurance, run by Yunliang Zhang.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 9 inclusion and 12 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 27 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Zhizheng REN (+8619862079078, 19862079078@163.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
1RM Squats and Bench Presses；Number of repetitions for 65% 1RM squats and bench presses (time frame: 5 week). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 27 Jul 2026; AzTrials last refreshed its copy on 7 Nov 2026.