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Completed

NCT Number: NCT07830459

Caffeine Dose and Duration in Habitual Female Users

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.

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Key information

Conditions

Caffeine Athletic Performance Resistance Traaining

Age range

20 year–30 year

Sex eligibility

Female

Study type

Interventional

Phase

Not applicable

Primary location

Faculty of Sport Sciences, University of Birjand

Birjand, South Khorasan Province, 9717434765, Iran

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

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) -

Exclusion criteria

Occurrence of any injury during the study

Failure to adhere to the supplement consumption protocol

Withdrawal from the study-

Treatment and study plan

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 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.

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.

Primary outcomes

  1. Change in Peak Power (PP) During Maximal Strength Test

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

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

Secondary outcomes

  1. Change in Peak Power During Strength-Endurance Test

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

    eak concentric power (Watts) during bench press at 50% of 1-RM to failure, measured using Kinect camera

  2. Change in Medicine Ball Throw Distance

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

    Distance (cm) of 3-kg medicine ball throw from chest position

  3. Change in Vertical Jump Height

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

    Countermovement jump height (cm) measured using Kinect camera

  4. Change in Number of Repetitions (Strength-Endurance)

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

    Number of repetitions performed at 50% of 1-RM until failure

Sponsors and collaborators

Lead sponsor

Birjand University of Medical Sciences

Other

Registry information

Official study title

Comparison Effects of Acute and Short-Term Consumption of Different Doses of Caffeine on Strength and Power Indices in Habitual Caffeine-Consuming Women

Important dates

Study start
2023
Primary completion
2023
Study completion
2023
First posted
Sep 21, 2026
Registry last updated
Sep 21, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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