The Effects of Caffeine on Exercise Physiology and Time-trial Performance in a Hot Environment

NCT ID: NCT07129200

Last Updated: 2025-08-19

Basic Information

• Recruitment Status: NOT_YET_RECRUITING
• Clinical Phase: NA
• Total Enrollment: 15 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-08-22
• Study Completion Date: 2026-06-30

Brief Summary

Maintaining a stable core temperature is vital for physiological function; yet, exercise in heat can be problematic, and there is risk of exertional heat-related illness (Flouris & Schlader, 2015; Leyk et al., 2019; Périard et al., 2021; Tyler et al., 2016; Veltmeijer et al., 2015). While aerobic fitness improves heat tolerance (Alhadad et al., 2019), strategies like acclimation and pre-cooling also mitigate heat stress (Casadio et al., 2016; Lorenzo et al., 2010; Ross et al., 2013; Siegel et al., 2010). Caffeine, an ergogenic aid (Del Corso et al., 2011; John et al., 2024), is known to enhance performance via adenosine antagonism and increased catecholamines in normothermic environments (Fredholm et al., 1999; Graham & Spriet, 1991). However, effects in heat are inconsistent (Ganio et al., 2009; Zhang et al., 2014), possibly due to caffeine reducing the ability to thermoregulate effectively. Therefore, the aim of this study is to investigate the effects of a moderate dose of caffeine (5 mg/kg) on thermoregulation during a 30-minute running time trial in 35°C heat.

Conditions

Caffeine; Thermoregulation

Study Design

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

Study Groups

Caffeine

5 mg/kg dose of caffeine (in pill form)

Group Type: EXPERIMENTAL

Hot environment

Intervention Type: OTHER

Hot environment of 35 degrees Celsius

Thermoneutral environment

Intervention Type: OTHER

Thermoneutral environment of 18 degrees Celsius

Placebo

5 mg/kg dose of placebo (maltodextrin - in pill form)

Group Type: PLACEBO_COMPARATOR

Hot environment

Intervention Type: OTHER

Hot environment of 35 degrees Celsius

Thermoneutral environment

Intervention Type: OTHER

Thermoneutral environment of 18 degrees Celsius

Interventions

Hot environment

Hot environment of 35 degrees Celsius

Intervention Type: OTHER

Thermoneutral environment

Thermoneutral environment of 18 degrees Celsius

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Healthy trained runners

Exclusion Criteria

-

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 45 Years
• Eligible Sex: MALE
• Accepts Healthy Volunteers: Yes

Sponsors

St. Mary's University, Twickenham

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Central Contacts

Mark Glaister

Role: CONTACT

mark.glaister@stmarys.ac.uk

+447957616552

Other Identifiers

SMU_ETHICS_2024-25_1111

Identifier Type: -

Identifier Source: org_study_id