Effect of Low-Dose Caffeine on Performance in Elite Sitting Volleyball Players

The Effect of Low Dose Caffeine on Serve Speed, Spike Speed, and Speed-Endurance in Elite Sitting Volleyball Players: A Randomized Double-Blind Crossover Study

Background: Sitting volleyball is a sport that relies primarily on upper body strength and anaerobic capacity. In critical in-game skills such as serve and spike, factors such as speed-endurance time and impact power play a decisive role in performance. There are limited studies in the literature examining the effects of low-dose caffeine consumption on these skills. The effects of ergogenic supplements in Paralympic sports have not been sufficiently investigated, and the potential benefits of caffeine on serve and spike performance in sitting volleyball players remain unclear. Purpose: The main purpose of this research was to determine the effects of low-dose caffeine (3 mg/kg) consumption on the serve speed, spike speed and Speed-Endurance performances of elite-level sitting volleyball players. Method: The study was designed using a randomized, double-blind, balanced, and crossover experimental design. 13 elite male athletes from the 2024 Paravolley European Champion Sitting Volleyball Men's National Team participated in the study. Participants were evaluated for serve speed, spike speed, and speed-endurance performances in both 3 mg/kg caffeine (CAF) and placebo (PLA) conditions.

Study Overview

• Status: Completed
• Conditions: Muscle Strength; Caffeine; Physical Endurance; Paralympic Athletes
• Intervention / Treatment: Dietary supplement: Caffeine; Dietary supplement: Placebo

Detailed Description

This study aimed to investigate the effects of low-dose caffeine ingestion on key performance parameters in elite-level sitting volleyball athletes. Sitting volleyball is a Paralympic sport that relies heavily on upper body explosive strength and short-term anaerobic power. While caffeine is a well-known ergogenic aid in able-bodied sports, its role in Paralympic contexts remains underexplored. Using a randomized, double-blind, placebo-controlled crossover design, the effects of 3 mg/kg caffeine consumption were assessed in 13 elite male sitting volleyball players. Each participant completed performance assessments under both caffeine and placebo conditions. The primary goal was to examine whether caffeine intake would enhance serve speed, spike speed, and repeated sprint ability. The study provides new insights into the acute ergogenic effects of caffeine in Paralympic team sport athletes, highlighting its selective benefit on explosive upper-body tasks such as serving.

• Study Type: Interventional
• Enrollment (Actual): 13
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey
  • Central
    • Karaman, Central, Turkey, 695002
      • Karamanoğlu Mehmetbey University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Male sitting volleyball players aged between 18 and 40
• Member of the 2024 National Sitting Volleyball Team
• At least 3 years of competitive playing experience
• No caffeine consumption 48 hours prior to testing
• Provided informed consent to participate

Exclusion Criteria:

• Known cardiovascular, neurological, or metabolic disorders
• Current use of medications that may affect caffeine metabolism
• Allergy or sensitivity to caffeine
• Use of performance-enhancing substances within the last month

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Low-Dose Caffeine Arm; Participants receive a single oral dose of caffeine (3 mg/kg) during the first session and a placebo in the second session. There is a washout period of at least 48 hours between sessions.	Dietary supplement: Caffeine; A single oral dose of 3 mg of caffeine per kilogram of body weight form approximately 60 minutes before performance testing. Supplied by Oxford Vitality, ISO-certified.; Dietary supplement: Placebo; polydextrose used as Placebo
Experimental: Placebo Arm; Participants receive a placebo during the first session and a single oral dose of caffeine (3 mg/kg) in the second session. There is a washout period of at least 48 hours between sessions.	Dietary supplement: Caffeine; A single oral dose of 3 mg of caffeine per kilogram of body weight form approximately 60 minutes before performance testing. Supplied by Oxford Vitality, ISO-certified.; Dietary supplement: Placebo; polydextrose used as Placebo

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Serve Speed	Serve speed will be assessed using a calibrated radar device to record peak velocity of each participant's volleyball serve.	After 60 minutes ingestion of the supplement on test day (CAF and PLA)
Spike Speed	Maximum spike speed will be measured in kilometers per hour (km/h) using a radar gun during a standardized spike task conducted after supplementation in each condition.	After 60 minutes ingestion of the supplement on test day (CAF and PLA)
Speed-Endurance	The number of maximal shuttle runs completed in a repeated sprint ability (RSA) test protocol will be recorded to assess speed-endurance capacity.	After 60 minutes ingestion of the supplement on test day (CAF and PLA)

Collaborators and Investigators

• Sponsor: Ulaç Can YILDIRIM
• Investigators: Study Chair: Ulas C Yildirim, sinop university faculty of sport sciences

Study record dates

Study Major Dates

• Study Start (Actual): March 5, 2025
• Primary Completion (Actual): March 11, 2025
• Study Completion (Actual): March 12, 2025

Study Registration Dates

• First Submitted: June 21, 2025
• First Submitted That Met QC Criteria: June 28, 2025
• First Posted (Actual): July 9, 2025

Study Record Updates

• Last Update Posted (Actual): July 9, 2025
• Last Update Submitted That Met QC Criteria: June 28, 2025
• Last Verified: June 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Molecular Mechanisms of Pharmacological Action; Enzyme Inhibitors; Neurotransmitter Agents; Purinergic Antagonists; Purinergic Agents; Central Nervous System Stimulants; Phosphodiesterase Inhibitors; Purinergic P1 Receptor Antagonists; Caffeine
• Other Study ID Numbers: 2025/91

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No