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

23. juli 2026 oppdatert av: 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.

Studieoversikt

Status

Har ikke rekruttert ennå

Forhold

Intervensjon / Behandling

Studietype

Intervensjonell

Registrering (Antatt)

40

Fase

  • Ikke aktuelt

Kontakter og plasseringer

Denne delen inneholder kontaktinformasjon for de som utfører studien, og informasjon om hvor denne studien blir utført.

Studiekontakt

Deltakelseskriterier

Forskere ser etter personer som passer til en bestemt beskrivelse, kalt kvalifikasjonskriterier. Noen eksempler på disse kriteriene er en persons generelle helsetilstand eller tidligere behandlinger.

Kvalifikasjonskriterier

Alder som er kvalifisert for studier

  • Voksen

Tar imot friske frivillige

Nei

Beskrivelse

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

Studieplan

Denne delen gir detaljer om studieplanen, inkludert hvordan studien er utformet og hva studien måler.

Hvordan er studiet utformet?

Designdetaljer

  • Primært formål: Behandling
  • Tildeling: Randomisert
  • Intervensjonsmodell: Sekvensiell tildeling
  • Masking: Dobbelt

Våpen og intervensjoner

Deltakergruppe / Arm
Intervensjon / Behandling
Eksperimentell: Kontroll
Atferdsmessig: 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].
Eksperimentell: caf
Atferdsmessig: 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].
Eksperimentell: VC
Atferdsmessig: 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].
Eksperimentell: caf+VC
Atferdsmessig: 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].

Hva måler studien?

Primære resultatmål

Resultatmål
Tidsramme
1RM Squats and Bench Presses；Number of repetitions for 65% 1RM squats and bench presses
Tidsramme: 5 week
5 week

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Sponsor

Yunliang Zhang

Studierekorddatoer

Disse datoene sporer fremdriften for innsending av studieposter og sammendragsresultater til ClinicalTrials.gov. Studieposter og rapporterte resultater gjennomgås av National Library of Medicine (NLM) for å sikre at de oppfyller spesifikke kvalitetskontrollstandarder før de legges ut på det offentlige nettstedet.

Studer hoveddatoer

Studiestart (Antatt)

25. juli 2026

Primær fullføring (Antatt)

20. september 2026

Studiet fullført (Antatt)

22. september 2026

Datoer for studieregistrering

Først innsendt

17. juli 2026

Først innsendt som oppfylte QC-kriteriene

21. juli 2026

Først lagt ut (Faktiske)

24. juli 2026

Oppdateringer av studieposter

Sist oppdatering lagt ut (Faktiske)

27. juli 2026

Siste oppdatering sendt inn som oppfylte QC-kriteriene

23. juli 2026

Sist bekreftet

1. juli 2026

Mer informasjon

Begreper knyttet til denne studien

Nøkkelord

Ytterligere relevante MeSH-vilkår

Andre studie-ID-numre

  • TJUS2026-30

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