The Effects of Caffeine and Vitamin C on Maximum Strength and Strength Endurance in Adolescents With Mild Mental Fatigue | NCT07726745

NCT07726745

Overview

NCT ID: NCT07726745
Lead Sponsor: Yunliang ZhangOTHER
Official Title: The Effects of Caffeine and Vitamin C on Maximum Strength and Strength Endurance in Adolescents With Mild Mental Fatigue
Brief 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. 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.

Status and Timeline

Status: Not yet recruiting
Last Update Posted: Jul 27, 2026Actual
Start Date: Jul 25, 2026Estimated
Primary Completion Date: Sep 20, 2026Estimated
Completion Date

Participation Criteria

Ages Eligible for Study: Adult (18-64)
Sexes Eligible for Study: Female
Accepts Healthy Volunteers?: No
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

Study Plan

Study Type: Interventional
Phase: Not Applicable
Enrollment: 40Estimated
Primary Purpose: Treatment
Allocation: Randomized
Interventional Model: Sequential Assignment
Masking: Double

Contacts and Locations

Central Contacts: Zhizheng RENContact
19862079078@163.com+8619862079078

Overview

Status and Timeline

Participation Criteria

Study Plan

Contacts and Locations

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