Effects of Creatine and Heat Exposure on Exercise Performance and Body Water Distribution

Creatine Monohydrate Supplementation During Repeated Heat Exposure: Effects on Fluid Balance and Exercise Performance in a Randomized Double-Blind, Placebo-Controlled Trial

The goal of this clinical trial is to learn whether creatine supplementation changes how the body adapts to repeated exercise in the heat in healthy recreationally active adults and varsity athletes. The study will also examine whether creatine affects fluid balance, blood volume changes and exercise performance.

The main questions it aims to answer are:

Does creatine supplementation increase plasma volume and total body water during repeated heat exposure more than placebo? Does creatine supplementation improve exercise performance after heat acclimation more than placebo? Does creatine supplementation influence cardiovascular responses to heat stress?

Researchers will compare a creatine supplementation group to a placebo group to determine whether creatine changes the magnitude of heat acclimation adaptations.

Participants will:

Complete baseline measurements of body composition, hydration, blood markers, and exercise performance.

Consume either creatine monohydrate or a placebo supplement daily Complete repeated supervised exercise sessions in a controlled heated environment Undergo repeated assessments of body water, temperature, heart rate, and exercise performance throughout the study

Study Overview

• Status: Not yet recruiting
• Conditions: Exercise Performance; Hydration; Plasma Volume; Heat Exposure; Body Fluid Compartments; Creatine Supplementation; Placebo - Control
• Intervention / Treatment: Dietary supplement: Creatine Monohydrate; Dietary supplement: Maltodextrin (Placebo)

Detailed Description

Heat acclimation (HA) is a physiological adaptation process that occurs following repeated exposure to hot environmental conditions. HA is associated with several beneficial cardiovascular and thermoregulatory adaptations, including plasma volume expansion, improved heat tolerance, lower physiological strain during exercise, and improved exercise performance in hot and temperate environments. However, substantial variability exists in the magnitude and rate of adaptation between individuals.

Creatine monohydrate supplementation is widely used to improve high-intensity exercise performance and is known to increase intracellular water retention within skeletal muscle. Because HA also influences fluid regulation and plasma volume expansion, creatine supplementation may alter fluid distribution and cardiovascular responses during repeated heat exposure. Despite this theoretical interaction, limited research has investigated the combined effects of creatine supplementation and HA on fluid balance and exercise performance.

The purpose of this randomized, double-blind, placebo-controlled trial is to examine whether creatine monohydrate supplementation influences body-fluid distribution, plasma volume expansion, and exercise performance during repeated heat exposure in healthy recreationally active males and varsity athletes.

Participants will complete baseline testing consisting of body composition assessment, body water measurement, capillary blood sampling, resting temperature assessment, and cardiorespiratory and musculoskeletal performance testing using cycle ergometry. Participants will then be randomly assigned to receive either creatine monohydrate or a placebo supplement under double-blind conditions.

The supplementation protocol will include a 7-day loading phase followed by a maintenance phase throughout the remainder of the study. Following supplementation, participants will complete 7 consecutive days of supervised heat exposure consisting of moderate-intensity cycling in a heated environment designed to elevate body temperature and induce heat acclimation adaptations.

Throughout the study, researchers will assess changes in plasma volume, total body water, resting temperature, heart rate responses, and exercise performance. Physiological monitoring will occur during all heat exposure sessions to support participant safety.

The findings from this study may improve understanding of how creatine supplementation influences fluid regulation and adaptation to heat stress. Results may have implications for athletes, physically active individuals, and occupational populations exposed to hot environmental conditions.

• Study Type: Interventional
• Enrollment (Estimated): 25
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Andrew S Perrotta, Phd; Phone Number: 604 679 7172; Email: Andrew.Perrotta@uwindsor.ca
• Study Contact Backup: Name: Benjamin R Tilson, (BSc); Phone Number: 519 819 7732; Email: tilsonb@uwindsor.ca

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Healthy biological males between 18 and 27 years of age
• Recreationally active males and varsity athletes
• Able to safely participate in moderate-intensity exercise and heat exposure
• Willing to maintain habitual diet and physical activity throughout the study
• Willing to refrain from additional dietary supplementation during study participation
• Able to attend all required laboratory visits and heat exposure sessions
• Able to provide informed consent

Exclusion Criteria:

• History of cardiovascular, metabolic, respiratory, renal, neurological, or heat-related illness
• Contraindications to exercise testing or heat exposure identified during health screening
• Current musculoskeletal injury limiting exercise participation
• Current use of creatine supplementation or inability to complete the required washout period
• Current use of medications or supplements known to affect hydration, thermoregulation, cardiovascular function, or exercise performance
• Known allergy or intolerance to creatine monohydrate, maltodextrin, or orange juice
• Inability to comply with study procedures or supplementation protocol
• Resting tympanic temperature ≥38.0°C prior to a heat exposure session
• Participation in another research study that may interfere with this protocol

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Creatine Monohydrate + Heat Exposure; Participants assigned to this arm will complete a 7-day creatine monohydrate loading phase followed by daily maintenance supplementation during a 7-day heat acclimation protocol. Participants will complete daily supervised heat exposure sessions consisting of cycling exercise in a controlled hot environment.	Dietary supplement: Creatine Monohydrate; Participants assigned to this intervention will consume micronized creatine monohydrate during a 7-day loading phase at 0.3 g·kg-¹·day-¹ followed by a maintenance dose of 0.03 g·kg-¹·day-¹ during the heat acclimation protocol. Supplements will be dissolved in orange juice and consumed under supervision during laboratory visits. Creatine supplementation will continue throughout the heat acclimation period.
Placebo Comparator: Placebo + Heat Exposure; Participants assigned to this arm will consume a placebo supplement (maltodextrin) matched in appearance and dosing schedule to the creatine condition during a 7-day heat acclimation protocol. Participants will complete daily supervised heat exposure sessions consisting of cycling exercise in a controlled hot environment.	Dietary supplement: Maltodextrin (Placebo); Participants will consume maltodextrin matched to creatine supplementation appearance and dosing schedule during the loading and maintenance phases of the study.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Plasma Volume Change Following Heat Acclimation and Creatine Supplementation	Percent change in plasma volume estimated from capillary blood hematocrit measurements. Following centrifugation, packed red blood cell volume and plasma layers will be measured using a microhematocrit reader, and hematocrit will be expressed as a percentage of total blood volume. Relative changes in blood volume and plasma volume will be inferred from repeated hematological measurements obtained at standardized time points throughout the study.	Measured at baseline (pre-supplementation), after 7 days of creatine/placebo loading, and after 7 days of heat acclimation.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Total Body Water	Total body water measured using bioelectrical impedance analysis (InBody 230).	Measured at baseline (pre-supplementation), after 7 days of creatine/placebo loading, and after 7 days of heat acclimation.
Change in Intracellular Water	Intracellular water estimated using bioelectrical impedance analysis.	Measured at baseline (pre-supplementation), after 7 days of creatine/placebo loading, and after 7 days of heat acclimation.
Change in Extracellular Water	Extracellular water estimated using bioelectrical impedance analysis.	Measured at baseline (pre-supplementation), after 7 days of creatine/placebo loading, and after 7 days of heat acclimation.
Change in VO₂ Peak	VO₂ peak assessed during supramaximal cycling exercise using breath-by-breath metabolic gas analysis.	Measured at baseline (pre-supplementation), after 7 days of creatine/placebo loading, and after 7 days of heat acclimation.
Change in Musculoskeletal Performance	Musculoskeletal performance assessed during supramaximal cycling exercise using peak and mean power output measures.	Measured at baseline (pre-supplementation), after 7 days of creatine/placebo loading, and after 7 days of heat acclimation.

Collaborators and Investigators

• Sponsor: University of Windsor

Publications and helpful links

General Publications

• Kreider RB, Kalman DS, Antonio J, Ziegenfuss TN, Wildman R, Collins R, Candow DG, Kleiner SM, Almada AL, Lopez HL. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr. 2017 Jun 13;14:18. doi: 10.1186/s12970-017-0173-z. eCollection 2017.
• Periard JD, Racinais S, Sawka MN. Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports. Scand J Med Sci Sports. 2015 Jun;25 Suppl 1:20-38. doi: 10.1111/sms.12408.
• Dill DB, Costill DL. Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration. J Appl Physiol. 1974 Aug;37(2):247-8. doi: 10.1152/jappl.1974.37.2.247. No abstract available.
• Wenger CB (2003). Human adaptation to hot environments. In K. B. Pandolf, M. N. Sawka, & R. R. Gonzalez (Eds.), Human performance physiology and environmental medicine at terrestrial extremes (pp. 379-438). Benchmark Press.
• Mack, G.W. and Nadel, E.R. (1994), Body Fluid Balance During Heat Stress in Humans. Comprehensive Physiology, 1994: 187-214. https://doi.org/10.1002/j.2040-4603.1994.tb01156.x
• Lorenzo S, Halliwill JR, Sawka MN, Minson CT. Heat acclimation improves exercise performance. J Appl Physiol (1985). 2010 Oct;109(4):1140-7. doi: 10.1152/japplphysiol.00495.2010. Epub 2010 Aug 19.

Study record dates

Study Major Dates

• Study Start (Estimated): July 30, 2026
• Primary Completion (Estimated): April 30, 2027
• Study Completion (Estimated): August 30, 2027

Study Registration Dates

• First Submitted: May 11, 2026
• First Submitted That Met QC Criteria: May 11, 2026
• First Posted (Actual): May 18, 2026

Study Record Updates

• Last Update Posted (Actual): May 18, 2026
• Last Update Submitted That Met QC Criteria: May 11, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Fluid Balance; Heat Exposure; Creatine Monohydrate; Plasma Volume; VO2 Max; Heat Acclimation; Wingate Test; Short Term Heat Acclimation; Body Fluid Compartments; Cardiorespiratory Performance; Musculoskeletal Performance
• Additional Relevant MeSH Terms: Amino Acids, Peptides, and Proteins; Organic Chemicals; Amino Acids; Guanidines; Amidines; maltodextrin; Creatine
• Other Study ID Numbers: #26-057

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