Cedar Falls

Researchers are investigating whether one week of creatine monohydrate supplementation affects inflammation, markers of acute kidney injury AKI risk, and cognitive performance in active, young, healthy adults. The study aims to find out if creatine changes urinary inflammation markers during exercise in heat, alters AKI risk markers, and lessens cognitive decline caused by fatigue from exertional heat stress compared to a placebo. This research involves a randomized, double-blind design comparing creatine to maltodextrin placebo. Participants will complete three visits a baseline visit and two exercise trials. At baseline, they undergo physical measurements, cognitive tests, and a maximal aerobic exercise test to determine cycling workload. For each exercise trial, participants will take 20 grams per day of creatine or placebo for seven days, plus 5 grams on the day of exercise. Exercise involves 90 minutes of cycling in a heated chamber at controlled temperature and humidity, alternating between low and high intensity. Urine and blood samples, core temperature via rectal thermistor, heart rate, and cognitive tests are collected before, during, and after exercise. Participants will self-collect urine samples before, immediately after, and one hour after exercise. They will also self-insert a rectal thermistor to measure core temperature and complete cognitive tasks using the NIH Toolbox before and after exercise. Various questionnaires assess mood, fatigue, thermal comfort, and gastrointestinal symptoms. Researchers will monitor hydration, body composition, blood pressure, and metabolic rate throughout the study. After a 21-day washout, participants complete the alternate supplementation trial. The primary outcome is the change in urinary biomarkers indicating AKI risk from before to after exercise in heat. Total participation spans several weeks including baseline and two exercise visits.