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
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
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
Parallel
Creatine Monohydrate
Dietary supplementParticipants 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.
Maltodextrin (Placebo)
Dietary supplementParticipants will consume maltodextrin matched to creatine supplementation appearance and dosing schedule during the loading and maintenance phases of the study.
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.
Change in Total Body Water
Total body water measured using bioelectrical impedance analysis (InBody 230).
Change in Intracellular Water
Intracellular water estimated using bioelectrical impedance analysis.
Change in Extracellular Water
Extracellular water estimated using bioelectrical impedance analysis.
Change in VO₂ Peak
VO₂ peak assessed during supramaximal cycling exercise using breath-by-breath metabolic gas analysis.
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