Effect of Caffeinated Chewing Gum on Vertical Jump Performance in Female Volleyball Players

NCT ID: NCT07240506

Last Updated: 2025-11-28

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 10 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-02-10
• Study Completion Date: 2025-05-01

Brief Summary

This study aimed to examine the acute effects of caffeine intake through caffeinated chewing gum on the vertical jump performance of professional female volleyball players. Ten athletes from the Turkish Women's Volleyball First League voluntarily participated in this single-blind, placebo-controlled, randomized crossover study. Each athlete completed two test sessions: one with caffeinated gum containing 200 mg of caffeine and one with a caffeine-free placebo gum. After chewing the gum for 5 minutes, participants performed three types of vertical jump tests: squat jump, countermovement jump, and block jump. The results showed that caffeinated gum significantly improved countermovement jump height compared with the placebo, while no significant differences were observed for squat or block jumps. The findings suggest that caffeine in gum form may enhance explosive performance in sports requiring rapid power output, such as volleyball.

Detailed Description

Caffeine is a well-established ergogenic aid known to improve endurance, strength, and cognitive performance. However, limited evidence exists on its acute effects in female team-sport athletes. This study was designed to evaluate the impact of acute caffeine intake via caffeinated chewing gum on vertical jump performance among professional female volleyball players. The research employed a randomized, single-blind, placebo-controlled crossover design.

Ten professional athletes aged 18-33 years from the Yeşilyurt Sports Club Women's A Team, competing in the Turkish Volleyball Federation Women's 1st League, were included. Participants underwent two experimental sessions: one involving caffeinated gum (CAF, 200 mg total caffeine from two 100 mg pieces) and one involving placebo gum (PLA, identical but caffeine-free), separated by a six-day washout period. The gums were chewed for 5 minutes, and jump performance tests were conducted 15 minutes later.

Vertical jump performance was evaluated using a Chronojump jump mat for three jump types: squat jump (SJ), countermovement jump (CMJ), and block jump (BJ). Each test included three attempts, with the highest score recorded for analysis. Data were analyzed with paired-sample t-tests using SPSS 27.0, with significance set at p<0.05.

The results showed that caffeine gum significantly increased CMJ height compared with the placebo (p<0.05), but no significant effects were observed for SJ or BJ performance. The findings indicate that caffeine in gum form may acutely improve explosive performance involving stretch-shortening cycle movements.

The study was approved by the Non-Interventional Clinical Research Ethics Committee of Istanbul Medipol University (Approval No: E-10840098-202.3.02-735). All participants provided informed consent prior to data collection.

Conditions

Athletic Performance

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: SINGLE

Study Groups

Caffeinated Gum (CAF)

Participants chewed two pieces of caffeinated chewing gum containing a total of 200 mg caffeine (2 × 100 mg). After chewing for 5 minutes, they performed squat jump, countermovement jump, and block jump tests.

Group Type: EXPERIMENTAL

Caffeinated chewing gum

Intervention Type: DIETARY_SUPPLEMENT

Two pieces of caffeinated chewing gum providing 200 mg total caffeine; administered 15 minutes before performance testing.

Placebo Gum (PLA)

Participants chewed two pieces of placebo chewing gum identical in appearance and flavor but containing no caffeine. After chewing for 5 minutes, they performed the same vertical jump tests as in the caffeinated condition.

Group Type: PLACEBO_COMPARATOR

Placebo chewing gum

Intervention Type: DIETARY_SUPPLEMENT

Two pieces of placebo chewing gum identical in appearance and flavor to the caffeinated gum but containing no caffeine; administered 15 minutes before performance testing.

Interventions

Caffeinated chewing gum

Two pieces of caffeinated chewing gum providing 200 mg total caffeine; administered 15 minutes before performance testing.

Intervention Type: DIETARY_SUPPLEMENT

Placebo chewing gum

Two pieces of placebo chewing gum identical in appearance and flavor to the caffeinated gum but containing no caffeine; administered 15 minutes before performance testing.

Intervention Type: DIETARY_SUPPLEMENT

Eligibility Criteria

Inclusion Criteria

Self-identified female athletes aged 18-33 years Professional volleyball players actively competing in the Turkish Women's Volleyball First League Minimum of 3 years of competitive volleyball experience Healthy individuals without any diagnosed medical conditions Willing to abstain from caffeine-containing products for at least 24 hours before each testing session Voluntarily agreed to participate and provided written informed consent

Exclusion Criteria

Known cardiovascular, metabolic, or neurological disorders Current use of medications or supplements affecting physical performance or caffeine metabolism Pregnancy or breastfeeding History of caffeine sensitivity, intolerance, or allergy Failure to comply with pre-test instructions (e.g., caffeine restriction, rest period) Musculoskeletal injuries preventing full jump performance

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 33 Years
• Eligible Sex: FEMALE
• Accepts Healthy Volunteers: Yes

Sponsors

Muttalip Ayar

OTHER

Sponsor Role: lead

Responsible Party

Muttalip Ayar

Assistant Professor

Responsibility Role: SPONSOR_INVESTIGATOR

Locations

Yeşilyurt Sports Club - Women's Volleyball Team Training Facility

Istanbul, Bakırköy, Turkey (Türkiye)

Countries

Turkey (Türkiye)

Other Identifiers

E-10840098-202.3.02-735

Identifier Type: -

Identifier Source: org_study_id