The Repeatability of the Effect of Caffeine Supplementation on Submaximal Physiological Responses and Cycling Time Trial Performance

Recently, Grgic (2018) discussed the concept of responders and non-responders to caffeine supplementation highlighting the importance of the repeatability of results. However, the number of studies that have investigated this idea by repeating the same time-trial performance test multiple times with the same caffeine dose is sparse (Astorino et al., 2012; Del Coso et al., 2019). Furthermore, studies have shown that differences in the CYP1A2 genotype may account for some of the variation in time-trial performance (Guest et al., 2018). Thus, the current study aims to identify whether the effects of moderate caffeine supplementation (5 mg/kg) on time-trial performance are repeatable to aid the identification of responders and non-responders. Additionally, the study aims to determine if the CYP1A2 genotype may explain any of the variability in time-trial performance in trained male cyclists.

Study Overview

• Status: Not yet recruiting
• Conditions: Caffeine
• Intervention / Treatment: Dietary supplement: Caffeine; Dietary supplement: Caffeine; Dietary supplement: Placebo

• Study Type: Interventional
• Enrollment (Estimated): 12
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• To be considered for inclusion in the study, participants must be regular cyclists, between 18 and 35 years of age, capable of completing a 20 km cycling time trial at a minimum speed of 30 km/h (arbitrary inclusion criteria to ensure a sufficient standard of athlete).

Exclusion Criteria:

-

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Caffeine; 5 mg/kg dose of caffeine (in pill form) - Trial 1	Dietary supplement: Caffeine; 5 mg/kg of caffeine in pill form; Dietary supplement: Caffeine; 5 mg/kg dose of caffeine in pill form
Placebo Comparator: Placebo; 5 mg/kg dose of placebo (Maltodextrin in pill form) - Trial 2	Dietary supplement: Placebo; 5 mg/kg dose of maltodextrin in pill form

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Blood lactate concentration	Description: Change from baseline in blood lactate concentration measured at rest and at six different exercise intensities (55, 60, 65, 70, 75, and 80% percent of maximal oxygen uptake) on an electromagnetically-braked cycle ergometer	From baseline to completion, up to 31 days
Heart rate	Change from baseline in heart rate measured at rest and at seven different exercise intensities (55, 60, 65, 70, 75, and 80% percent of maximal oxygen uptake) on an electromagnetically-braked cycle ergometer.	From baseline to completion, up to 31 days
Oxygen uptake	Change from baseline in oxygen uptake measured at rest and at seven different exercise intensities (55, 60, 65, 70, 75, and 80% percent of maximal oxygen uptake) on an electromagnetically-braked cycle ergometer	From baseline to completion, up to 31 days
Perceived exertion	Change from baseline in rating of perceived exertion measured (using the 6-20 Borg scale) at seven different exercise intensities (55, 60, 65, 70, 75, and 80% percent of maximal oxygen uptake) on an electromagnetically-braked cycle ergometer	From baseline to completion, up to 31 days
Time trial completion time	Change from baseline in time to complete a time trial at a target amount of work on an electromagnetically-braked cycle ergometer calculated from the power output at maximal oxygen uptake and designed to last approximately 25 minutes.	From baseline to completion, up to 31 days

Collaborators and Investigators

• Sponsor: St. Mary's University, Twickenham

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2025
• Primary Completion (Estimated): August 23, 2025
• Study Completion (Estimated): December 31, 2025

Study Registration Dates

• First Submitted: April 11, 2025
• First Submitted That Met QC Criteria: April 11, 2025
• First Posted (Actual): April 20, 2025

Study Record Updates

• Last Update Posted (Actual): April 20, 2025
• Last Update Submitted That Met QC Criteria: April 11, 2025
• Last Verified: April 1, 2025

More Information

Terms related to this study

• Keywords: genetics; caffeine; cycling; time trial
• 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: SMU_ETHICS_2024-25_992

Drug and device information, study documents

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