Investigating Respiratory Frequency as a Core Temperature Proxy in Division 1 American Football

Exertional heat illness (EHI) is a leading cause of preventable sudden death in sports. American football (AmFb) accounts for 75% of reported heat-related illnesses in NCAA sports. EHI fatalities in AmFb have surpassed those from direct trauma since 1990, mainly occurring during preseason practices when wet bulb globe temperatures (WBGT) exceed 27.8°C. Although internal temperature monitoring has been explored, the relationship between electrocardiogram-derived respiratory frequency (EDR) and core temperature (Tc) remains undefined. PURPOSE: This study aims to evaluate EDR as a non-invasive, real-time monitoring strategy for heat stress compared to ECG-Tc during preseason practices. METHODS: Six University of Utah football players (20.3 ± 1.6 years) were recruited for the study. Following the pilot phase, data collection occurred during early preseason, which included observing back-to-back afternoon practice sessions. Participants ingested a BodyCap thermometer capsule the morning of their first scheduled practice to measure Tc. Physiological data (e.g., heart rate) were collected with ECG-integrated Catapult sensors. Individuals met with the researcher following observed sessions to synthesize data. Practice conditions were also documented. Investigators preprocessed and analyzed data in RStudio. RESULTS: Preliminary Pearson correlation analyses showed a moderate, positive relationship between measured Tc and HR-derived Tc estimates (r = 0.52, p < 0.001), but no significant relationship with EDR (r = 0.34, p = 0.57); additional data will be incorporated as analyses progress. CONCLUSION: Early findings indicate that ECG-Tc better represents actual Tc values than EDR; ongoing analyses will further inform ecological monitoring strategies to support athlete safety.