Caffeine Dose and Duration in Habitual Female Users

NCT07830459 | Completed

• 1 other identifier: IR.BIRJAND.REC.1401.012
• Study Type: interventional
• Target: 36
• Locations: 1 country
• Sites: 1

Brief Summary

This study compares the effects of acute (single-session) and short-term (7-day) consumption of different doses of caffeine (3 and 6 mg/kg) on maximal strength, strength endurance, vertical jump, and medicine ball throw performance in habitual caffeine-consuming women (daily intake of 5 mg/kg). Thirty-six resistance-trained women were randomly assigned to three groups: 3 mg/kg caffeine, 6 mg/kg caffeine, or placebo in a double-blind crossover design. Participants completed both acute (60 min pre-exercise) and short-term (7 consecutive days) protocols. The main findings showed that acute ingestion of 6 mg/kg caffeine impaired peak power in the maximal strength test, while short-term consumption of the same dose improved peak power in the strength-endurance test. The 3 mg/kg dose was ineffective in all conditions. Caffeine did not affect jump or throw performance. The study highlights the need for individualized caffeine guidelines based on timing, dosage, and habituation status.

Conditions

Caffeine; Athletic Performance; Resistance Traaining

Outcome Measures

Primary Outcomes (1)

• Change in Peak Power (PP) During Maximal Strength Test

  Peak concentric power (Watts) during 1-RM bench press test, measured using a validated Kinect camera

  Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)

Secondary Outcomes (4)

• Change in Peak Power During Strength-Endurance Test

  Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)

• Change in Medicine Ball Throw Distance

  Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)

• Change in Vertical Jump Height

  Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)

• Change in Number of Repetitions (Strength-Endurance)

  Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)

Study Arms (3)

Caffeine 3 mg/kg

EXPERIMENTAL

Participants received 3 mg/kg body weight of caffeine powder in gelatin capsules daily for 7 days. Acute consumption: 60 minutes before testing. Short-term consumption: 7 consecutive days

Dietary Supplement: Caffeine 3 mg/kg

Caffeine 6 mg/kg

EXPERIMENTAL

Participants received 6 mg/kg body weight of caffeine powder in gelatin capsules daily for 7 days. Acute consumption: 60 minutes before testing. Short-term consumption: 7 consecutive days

Dietary Supplement: Caffeine 6 mg/kg

Placebo

PLACEBO COMPARATOR

Participants received identical capsules containing flour, consumed daily for 7 days

Dietary Supplement: Placebo

Interventions

Caffeine 3 mg/kg DIETARY_SUPPLEMENT

Caffeine powder (99% purity) encapsulated in gelatin capsules at a dose of 3 mg per kilogram of body weight. The capsules are identical in appearance, odor, and taste to the placebo. Participants consume the capsules daily for 7 consecutive days. On the testing day, the capsules are ingested 60 minutes prior to the exercise tests.

Caffeine 3 mg/kg

Caffeine 6 mg/kg DIETARY_SUPPLEMENT

Caffeine powder (99% purity) encapsulated in gelatin capsules at a dose of 6 mg per kilogram of body weight. The capsules are identical in appearance, odor, and taste to the placebo. Participants consume the capsules daily for 7 consecutive days. On the testing day, the capsules are ingested 60 minutes prior to the exercise tests.

Caffeine 6 mg/kg

Placebo DIETARY_SUPPLEMENT

Placebo capsules containing inert flour (or microcrystalline cellulose), identical in appearance, odor, and taste to the caffeine capsules. Participants consume the capsules daily for 7 consecutive days. On the testing day, the capsules are ingested 60 minutes prior to the exercise tests.

Placebo

Eligibility Criteria

• Age: 20 Years - 30 Years
• Sex: female
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Absence of neuromuscular and musculoskeletal disorders
• At least 2 years of regular resistance training experience (minimum 3 sessions per week)
• At least 6 months of resistance training prior to enrollment
• Absence of renal and hepatic disorders
• Daily caffeine consumption of 5 mg/kg body weight (based on questionnaire)
• No use of specific medications or supplements that could affect study outcomes (e.g., beta-alanine, creatine, pre-workout supplements) -

You may not qualify if:

• Occurrence of any injury during the study
• Failure to adhere to the supplement consumption protocol
• Withdrawal from the study-

Sponsors & Collaborators

• Birjand University of Medical Sciences: lead

Study Sites (1)

Faculty of Sport Sciences, University of Birjand

Birjand, South Khorasan Province, 9717434765, Iran

Location

MeSH Terms

Interventions

Caffeine

Intervention Hierarchy (Ancestors)

Xanthines; Alkaloids; Heterocyclic Compounds; Purinones; Purines; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Masking Details: Double Blind
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor of Exercise Physiology

Study Record Dates

• First Submitted: September 15, 2026
• First Posted: September 21, 2026
• Study Start: February 12, 2023
• Primary Completion: March 20, 2023
• Study Completion: March 30, 2023
• Last Updated: September 21, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

IR (1)