The Effects of Caffeine and Vitamin C on Maximum Strength and Strength Endurance in Adolescents With Mild Mental Fatigue
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- The protocol lists: 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses.
- Who it may be relevant to
- Registry conditions: Maximum Force, Strength Endurance, Mental Fatigue. Basic parameters: 18 years — 19 years · Female.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- Center list to be confirmed — check the primary protocol.
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
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Overview
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.
Interventions
- Behavioral 1RM squats and bench presses; repetitions at 65% of 1RM for squats and bench presses
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
Primary outcome measures
- 1RM Squats and Bench Presses；Number of repetitions for 65% 1RM squats and bench presses [Time frame: 5 week]
Eligibility criteria
Inclusion criteria
- 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
- 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
Exclusion criteria
- 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
- 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
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: No
Study design
- Allocation
- Randomized
- Model
- Sequential
- Masking
- Double blind
- Primary purpose
- Treatment
Study locations
Center list to be confirmed — check the primary protocol.
Identifiers
NCT: NCT07726745 · TJUS2026-30