Firefighter Thermoregulatory Responses in Active Fire With Betaine Supplementation (FFBET)

The goal of this clinical trial is to compare betaine supplementation to placebo in firefighters undergoing live burn training regarding thermoregulation and inflammation. The main questions it aims to answer are: Does betaine supplementation mitigate rises in core temperature during firefighter live burn training? Does betaine supplementation decrease inflammation from firefighter training? Does betaine supplementation increase total body water stores? Participants will supplement with betaine for 1 month and complete: Total Body Water measures Body Composition measures Live Burn training with Core Temperature Measurements Provide Salivary samples

Determine if BET supplementation impacts the thermal response in professional firefighters during live burn training.

To address Aim 1, we will measure and record changes in core temperature and skin temperature. Temperature will be measured before, during, and after the live burn. Physiological strain index will be calculated based off initial core temperature and heart rate, as well as ending core temperature and heart rate during the live burn. Tegaderm patches will be worn during the live burn to analyze sodium concentration in sweat. Additionally, subjective thermal sensation, rate of perceived exertion, and thirst will be measured before and after the live burn.

Determine if BET supplementation impacts acute physiological stress in professional firefighters during a live burn.

To address Aim 2, we will collect saliva samples before, immediately after, 10 minutes, and 20 minutes after live burn. These saliva samples will be analyzed for cortisol and testosterone to determine Testosterone Cortisol ratios and markers of inflammation (Interleukin 8 [IL-8] and interleukin-6 [IL-6]). Additionally, heart rate will be measured throughout the live burn. Last, pounds per square inch (PSI) in the firefighter's air tank will be recorded to indicate the amount of air usage.

Determine if BET supplementation decreases chronic physiological stress in professional firefighters.

To address Aim 3, we will collect saliva samples before and after the 4-week supplementation period to be analyzed for testosterone, cortisol, uric acid, and c-reactive protein. Resting blood pressure, total body water, and heart rate will also be measured.

Inclusion Criteria: Structural Firefighter Exclusion Criteria: • Participants have a cardiometabolic disease for which they take prescribed medications Participants consume supplements known to impact hydration status or performance that they are not willing to stop taking for the study Participants are pregnant Female participants that have irregular menstrual cycles Participants are injured and would not be able to fulfill the live burn scenario Participants have sickle cell disease Participants have experienced heat stroke within the last 2 years