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

23 juillet 2026 mis à jour par: Yunliang Zhang

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.

Aperçu de l'étude

Statut

Pas encore de recrutement

Les conditions

Intervention / Traitement

Type d'étude

Interventionnel

Inscription (Estimé)

40

Phase

  • N'est pas applicable

Contacts et emplacements

Cette section fournit les coordonnées de ceux qui mènent l'étude et des informations sur le lieu où cette étude est menée.

Coordonnées de l'étude

Critères de participation

Les chercheurs recherchent des personnes qui correspondent à une certaine description, appelée critères d'éligibilité. Certains exemples de ces critères sont l'état de santé général d'une personne ou des traitements antérieurs.

Critère d'éligibilité

Âges éligibles pour étudier

  • Adulte

Accepte les volontaires sains

Non

La description

Inclusion Criteria:

  1. Aged between 18and 19years (adolescent)
  2. Able to complete standardized 1RM maximal strength test and muscular endurance protocol for back squat and bench press
  3. Meet criteria for mild mental fatigue verified by validated scale (PVT + VAS Mental Fatigue ≥4/10 or Brief Fatigue Inventory) prior to experimental session
  4. Habitual daily caffeine intake ≤ 150 mg/day (low-to-moderate habitual consumption)
  5. Non-smoker; no regular alcohol consumption
  6. Consistent strength training status: No physical training for the past 3 months, or maintenance of a consistent daily activity routine throughout the study
  7. Able to attend all scheduled testing visits, comply with pre-test restrictions (diet, sleep, exercise, supplements)
  8. Participant provides written assent; parent/legal guardian provides written informed consent
  9. Able to understand and follow verbal and written study instructions

Exclusion Criteria:

  1. History of cardiovascular disease, arrhythmia, hypertension, asthma requiring regular medication
  2. Known hypersensitivity or adverse reaction to caffeine, vitamin C
  3. Chronic neurological disorders: epilepsy, migraine disorder, ADHD with stimulant medication
  4. Current psychiatric diagnosis (anxiety, depression) receiving psychotropic medication
  5. Musculoskeletal injury in the past 3 months limiting lower/upper body maximal strength testing
  6. Regular intake of ergogenic supplements (creatine, beta-alanine, energy drinks) within 4 weeks before screening
  7. Use of any stimulants, anti-fatigue drugs, corticosteroids within 30 days prior to enrollment
  8. Chronic gastrointestinal disease, kidney stone history (vitamin C related risk)
  9. Irregular sleep-wake cycle, diagnosed sleep disorder
  10. Females: current pregnancy; regular oral contraceptive use
  11. Participated in other human intervention trials within past 8 weeks
  12. Investigator judges any condition that compromises participant safety or interferes with outcome measurements

Plan d'étude

Cette section fournit des détails sur le plan d'étude, y compris la façon dont l'étude est conçue et ce que l'étude mesure.

Comment l'étude est-elle conçue ?

Détails de conception

  • Objectif principal: Traitement
  • Répartition: Randomisé
  • Modèle interventionnel: Affectation séquentielle
  • Masquage: Double

Armes et Interventions

Groupe de participants / Bras
Intervention / Traitement
Expérimental: Contrôler
Comportemental: 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 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].
Expérimental: caf
Comportemental: 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 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].
Expérimental: VC
Comportemental: 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 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].
Expérimental: caf+VC
Comportemental: 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 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].

Que mesure l'étude ?

Principaux critères de jugement

Mesure des résultats
Délai
1RM Squats and Bench Presses；Number of repetitions for 65% 1RM squats and bench presses
Délai: 5 week
5 week

Collaborateurs et enquêteurs

C'est ici que vous trouverez les personnes et les organisations impliquées dans cette étude.

Parrainer

Yunliang Zhang

Dates d'enregistrement des études

Ces dates suivent la progression des dossiers d'étude et des soumissions de résultats sommaires à ClinicalTrials.gov. Les dossiers d'étude et les résultats rapportés sont examinés par la Bibliothèque nationale de médecine (NLM) pour s'assurer qu'ils répondent à des normes de contrôle de qualité spécifiques avant d'être publiés sur le site Web public.

Dates principales de l'étude

Début de l'étude (Estimé)

25 juillet 2026

Achèvement primaire (Estimé)

20 septembre 2026

Achèvement de l'étude (Estimé)

22 septembre 2026

Dates d'inscription aux études

Première soumission

17 juillet 2026

Première soumission répondant aux critères de contrôle qualité

21 juillet 2026

Première publication (Réel)

24 juillet 2026

Mises à jour des dossiers d'étude

Dernière mise à jour publiée (Réel)

27 juillet 2026

Dernière mise à jour soumise répondant aux critères de contrôle qualité

23 juillet 2026

Dernière vérification

1 juillet 2026

Plus d'information

Termes liés à cette étude

Mots clés

Termes MeSH pertinents supplémentaires

Autres numéros d'identification d'étude

  • TJUS2026-30

Plan pour les données individuelles des participants (IPD)

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OUI

Description du régime IPD

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Informations sur les médicaments et les dispositifs, documents d'étude

Étudie un produit pharmaceutique réglementé par la FDA américaine

Non

Étudie un produit d'appareil réglementé par la FDA américaine

Non

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